Brownian motion of solitons in a Bose–Einstein condensate

PubMed Central

Aycock, Lauren M.; Hurst, Hilary M.; Efimkin, Dmitry K.; Genkina, Dina; Lu, Hsin-I; Galitski, Victor M.; Spielman, I. B.

2017-01-01

We observed and controlled the Brownian motion of solitons. We launched solitonic excitations in highly elongated Rb87 Bose–Einstein condensates (BECs) and showed that a dilute background of impurity atoms in a different internal state dramatically affects the soliton. With no impurities and in one dimension (1D), these solitons would have an infinite lifetime, a consequence of integrability. In our experiment, the added impurities scatter off the much larger soliton, contributing to its Brownian motion and decreasing its lifetime. We describe the soliton’s diffusive behavior using a quasi-1D scattering theory of impurity atoms interacting with a soliton, giving diffusion coefficients consistent with experiment. PMID:28196896

Theoretical study of impurity effects in iron-based superconductors

NASA Astrophysics Data System (ADS)

Navarro Gastiasoro, Maria; Hirschfeld, Peter; Andersen, Brian

2013-03-01

Several open questions remain unanswered for the iron-based superconductors (FeSC), including the importance of electronic correlations and the symmetry of the superconducting order parameter. Motivated by recent STM experiments which show a fascinating variety of resonant defect states in FeSC, we adopt a realistic five-band model including electronic Coulomb correlations to study local effects of disorder in the FeSC. In order to minimize the number of free parameters, we use the pairing interactions obtained from spin-fluctuation exchange to determine the homogeneous superconducting state. The ability of local impurity potentials to induce resonant states depends on their scattering strength Vimp; in addition, for appropriate Vimp, such states are associated with local orbital- and magnetic order. We investigate the density of states near such impurities and show how tunneling experiments may be used to probe local induced order. In the SDW phase, we show how C2 symmetry-breaking dimers are naturally formed around impurities which also form cigar-like (pi,pi) structures embedded in the (pi,0) magnetic bulk phase. Such electronic dimers have been shown to be candidates for explaining the so-called nematogens observed previously by QPI in Co-doped CaFe2As2.

Theoretical Study of Radiation from a Broad Range of Impurity Ions for Magnetic Fusion Diagnostics

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

Safronova, Alla

Spectroscopy of radiation emitted by impurities plays an important role in the study of magnetically confined fusion plasmas. The measurements of these impurities are crucial for the control of the general machine conditions, for the monitoring of the impurity levels, and for the detection of various possible fault conditions. Low-Z impurities, typically present in concentrations of 1%, are lithium, beryllium, boron, carbon, and oxygen. Some of the common medium-Z impurities are metals such as iron, nickel, and copper, and high-Z impurities, such as tungsten, are present in smaller concentrations of 0.1% or less. Despite the relatively small concentration numbers, themore » aforementioned impurities might make a substantial contribution to radiated power, and also influence both plasma conditions and instruments. A detailed theoretical study of line radiation from impurities that covers a very broad spectral range from less than 1 Å to more than 1000 Å has been accomplished and the results were applied to the LLNL Electron Beam Ion Trap (EBIT) and the Sustained Spheromak Physics Experiment (SSPX) and to the National Spherical Torus Experiment (NSTX) at Princeton. Though low- and medium-Z impurities were also studied, the main emphasis was made on the comprehensive theoretical study of radiation from tungsten using different state-of-the-art atomic structure codes such as Relativistic Many-Body Perturbation Theory (RMBPT). The important component of this research was a comparison of the results from the RMBPT code with other codes such as the Multiconfigurational Hartree–Fock developed by Cowan (COWAN code) and the Multiconfiguration Relativistic Hebrew University Lawrence Atomic Code (HULLAC code), and estimation of accuracy of calculations. We also have studied dielectronic recombination, an important recombination process for fusion plasma, for variety of highly and low charged tungsten ions using COWAN and HULLAC codes. Accurate DR rate coefficients are needed for describing the ionization balance of plasmas, which in turn determines the lines contributing to the spectral emission and the radiative power loss. In particular, we have calculated relativistic atomic data and corresponding dielectronic satellite spectra of highly ionized W ions, such as, for example, Li-like W (with the shortest wavelength of x-ray radiation of about 0.2 Å) that might exist in ITER core plasmas at very high temperatures of 30-40 keV. In addition, we have completed relativistic calculations of low ionized W ions from Lu-like (W3+) to Er-like (W6+) and for Sm-like(W12+) and Pm-like (W13+) that cover a spectral range from few hundred to thousand Å and are more relevant to the edge plasma diagnostics in tokamak.« less

Settling of virgin olive oil from horizontal screw solid bowl in static conditions.

PubMed

Gila, Abraham M; Bejaoui, Mohamed A; Beltrán, Gabriel; Jiménez, Antonio

2017-08-01

This work was aimed to study the clarification efficiency of natural decantation in settling tank on virgin olive oil obtained from a two-ways continuous process. For this purpose, the impurities content of the virgin olive oil were monitored during settling process in settling tank at two different depths. Efficiency of purging system was determined for two days. The experiments were performed at industrial scale during three crop years. During the first minutes of settling was observed an ascent of the smaller organic particles of the oil. Then, most of the virgin olive oil impurities were settled at 300 min, independently of the initial content of virgin olive oil. Finally, oil decantation showed slower rate. Higher clarification values were obtained for those decanter oils with higher impurities content, achieving clarification percentages between of 62.69 and 95.91% at 48 h of settling. The highest settling efficiency was observed for those decanter oils with initial higher impurities content. The purging system used in the settling tanks was not able to remove the most of settled impurities since a considerable amount of the impurities remained in the tank after 48 h, between 13.6 and 71.41% for the studied oils. In the tank purges was observed important oil losses. Therefore, decantation was not an efficient system for oil clarification since its settling capacity varied depending on the initial impurities content and due to the settled impurities can not be removed fully by purging system.

Effect of impurities on optical properties of pentaerythritol tetranitrate

NASA Astrophysics Data System (ADS)

Tsyshevskiy, Roman; Sharia, Onise; Kuklja, Maija M.

2012-03-01

Despite numerous efforts, the electronic nature of initiation of high explosives to detonation in general and mechanisms of their sensitivity to laser initiation in particular are far from being completely understood. Recent experiments show that Nd:YAG laser irradiation (at 1064nm) causes resonance explosive decomposition of PETN samples. In an attempt to shed some light on electronic excitations and to develop a rigorous interpretation to these experiments, the electronic structure and optical properties of PETN and a series of common impurities were studied. Band gaps (S0→S1) and optical singlet-triplet (S0→T1) transitions in both an ideal material and PETN containing various defects were simulated by means of state-of-the-art quantum-chemical computational techniques. It was shown that the presence of impurities in the PETN crystal causes significant narrowing of the band gap. The structure and role of molecular excitons in PETN are discussed.

The application of structure-based assessment to support safety and chemistry diligence to manage genotoxic impurities in active pharmaceutical ingredients during drug development.

PubMed

Dobo, Krista L; Greene, Nigel; Cyr, Michelle O; Caron, Stéphane; Ku, Warren W

2006-04-01

Starting materials and intermediates used to synthesize pharmaceuticals are reactive in nature and may be present as impurities in the active pharmaceutical ingredient (API) used for preclinical safety studies and clinical trials. Furthermore, starting materials and intermediates may be known or suspected mutagens and/or carcinogens. Therefore, during drug development due diligence need be applied from two perspectives (1) to understand potential mutagenic and carcinogenic risks associated with compounds used for synthesis and (2) to understand the capability of synthetic processes to control genotoxic impurities in the API. Recently, a task force comprised of experts from pharmaceutical industry proposed guidance, with recommendations for classification, testing, qualification and assessing risk of genotoxic impurities. In our experience the proposed structure-based classification, has differentiated 75% of starting materials and intermediates as mutagenic and non-mutagenic with high concordance (92%) when compared with Ames results. Structure-based assessment has been used to identify genotoxic hazards, and prompted evaluation of fate of genotoxic impurities in API. These two assessments (safety and chemistry) culminate in identification of genotoxic impurities known or suspected to exceed acceptable levels in API, thereby triggering actions needed to assure appropriate control and measurement methods are in place. Hypothetical case studies are presented demonstrating this multi-disciplinary approach.

Non-magnetic impurity effects in LiFeAs studied by STM/STS

NASA Astrophysics Data System (ADS)

Hanaguri, T.; Khim, Seung Hyun; Lee, Bumsung; Kim, Kee Hoon; Kitagawa, K.; Matsubayashi, K.; Mazaki, Y.; Uwatoko, Y.; Takigawa, M.; Takagi, H.

2012-02-01

Detecting the possible sign reversal of the superconducting gap in iron-based superconductors is highly non-trivial. Here we use non-magnetic impurity as a sign indicator. If the sign of the superconducting gap is positive everywhere in momentum space, in-gap bound state should not be observed near the impurity site unless it is magnetic. On the other hand, if there is a sign-reversal in the gap, even non-magnetic impurity may create in-gap bound state [1]. We performed STM/STS experiments on self-flux and Sn-flux grown LiFeAs crystals and examined the effects of Sn impurity. In STM images of Sn-flux grown samples, we found a ring-like object which may represent Sn. Tunneling spectrum taken at this defect site exhibits in-gap bound state. Together with flat-bottom superconducting gap observed far from the defects, sign-reversing s-wave gap is the most plausible gap structure in LiFeAs. [1] T. Kariyado and M. Ogata, JPSJ 79, 083704 (2010).

Absolute intensity measurements of impurity emissions in a shock tunnel and their consequences for laser-induced fluorescence experiments

NASA Technical Reports Server (NTRS)

Palma, P. C.; Houwing, A. F. P.; Sandeman, R. J.

1993-01-01

Absolute intensity measurements of impurity emissions in a shock tunnel nozzle flow are presented. The impurity emission intensities were measured with a photomultiplier and optical multichannel analyzer and calibrated against an intensity standard. The various metallic contaminants were identified and their intensities measured in the spectral regions 290 to 330 nm and 375 to 385 nm. A comparison with calculated fluorescence intensities for predissociated laser-induced fluorescence signals is made. It is found that the emission background is negligible for most fluorescence experiments.

Tunneling spectroscopy of a phosphorus impurity atom on the Ge(111)-(2 × 1) surface

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

Savinov, S. V.; Oreshkin, A. I., E-mail: oreshkin@spmlab.phys.msu.su, E-mail: oreshkin@spmlab.ru; Oreshkin, S. I.

2015-06-15

We numerically model the Ge(111)-(2 × 1) surface electronic properties in the vicinity of a P donor impurity atom located near the surface. We find a notable increase in the surface local density of states (LDOS) around the surface dopant near the bottom of the empty surface state band π*, which we call a split state due to its limited spatial extent and energetic position inside the band gap. We show that despite the well-established bulk donor impurity energy level position at the very bottom of the conduction band, a surface donor impurity on the Ge(111)-(2 × 1) surface mightmore » produce an energy level below the Fermi energy, depending on the impurity atom local environment. It is demonstrated that the impurity located in subsurface atomic layers is visible in a scanning tunneling microscope (STM) experiment on the Ge(111)-(2 × 1) surface. The quasi-1D character of the impurity image, observed in STM experiments, is confirmed by our computer simulations with a note that a few π-bonded dimer rows may be affected by the presence of the impurity atom. We elaborate a model that allows classifying atoms on the experimental low-temperature STM image. We show the presence of spatial oscillations of the LDOS by the density-functional theory method.« less

Experimental studies of collisional plasma shocks and plasma interpenetration via merging supersonic plasma jets

NASA Astrophysics Data System (ADS)

Hsu, S. C.; Moser, A. L.; Merritt, E. C.; Adams, C. S.

2015-11-01

Over the past 4 years on the Plasma Liner Experiment (PLX) at LANL, we have studied obliquely and head-on-merging supersonic plasma jets of an argon/impurity or hydrogen/impurity mixture. The jets are formed/launched by pulsed-power-driven railguns. In successive experimental campaigns, we characterized the (a) evolution of plasma parameters of a single plasma jet as it propagated up to ~ 1 m away from the railgun nozzle, (b) density profiles and 2D morphology of the stagnation layer and oblique shocks that formed between obliquely merging jets, and (c) collisionless interpenetration transitioning to collisional stagnation between head-on-merging jets. Key plasma diagnostics included a fast-framing CCD camera, an 8-chord visible interferometer, a survey spectrometer, and a photodiode array. This talk summarizes the primary results mentioned above, and highlights analyses of inferred post-shock temperatures based on observations of density gradients that we attribute to shock-layer thickness. We also briefly describe more recent PLX experiments on Rayleigh-Taylor-instability evolution with magnetic and viscous effects, and potential future collisionless shock experiments enabled by low-impurity, higher-velocity plasma jets formed by contoured-gap coaxial guns. Supported by DOE Fusion Energy Sciences and LANL LDRD.

Insulator-semimetallic transition in quasi-1D charged impurity-infected armchair boron-nitride nanoribbons

NASA Astrophysics Data System (ADS)

Dinh Hoi, Bui; Yarmohammadi, Mohsen

2018-04-01

We address control of electronic phase transition in charged impurity-infected armchair-edged boron-nitride nanoribbons (ABNNRs) with the local variation of Fermi energy. In particular, the density of states of disordered ribbons produces the main features in the context of pretty simple tight-binding model and Green's functions approach. To this end, the Born approximation has been implemented to find the effect of π-band electron-impurity interactions. A modulation of the π-band depending on the impurity concentrations and scattering potentials leads to the phase transition from insulator to semimetallic. We present here a detailed physical meaning of this transition by studying the treatment of massive Dirac fermions. From our findings, it is found that the ribbon width plays a crucial role in determining the electronic phase of disordered ABNNRs. The obtained results in controllable gap engineering are useful for future experiments. Also, the observations in this study have also fueled interest in the electronic properties of other 2D materials.

Characterization and validation of an in silico toxicology model to predict the mutagenic potential of drug impurities*

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

Valerio, Luis G., E-mail: luis.valerio@fda.hhs.gov; Cross, Kevin P.

Control and minimization of human exposure to potential genotoxic impurities found in drug substances and products is an important part of preclinical safety assessments of new drug products. The FDA's 2008 draft guidance on genotoxic and carcinogenic impurities in drug substances and products allows use of computational quantitative structure–activity relationships (QSAR) to identify structural alerts for known and expected impurities present at levels below qualified thresholds. This study provides the information necessary to establish the practical use of a new in silico toxicology model for predicting Salmonella t. mutagenicity (Ames assay outcome) of drug impurities and other chemicals. We describemore » the model's chemical content and toxicity fingerprint in terms of compound space, molecular and structural toxicophores, and have rigorously tested its predictive power using both cross-validation and external validation experiments, as well as case studies. Consistent with desired regulatory use, the model performs with high sensitivity (81%) and high negative predictivity (81%) based on external validation with 2368 compounds foreign to the model and having known mutagenicity. A database of drug impurities was created from proprietary FDA submissions and the public literature which found significant overlap between the structural features of drug impurities and training set chemicals in the QSAR model. Overall, the model's predictive performance was found to be acceptable for screening drug impurities for Salmonella mutagenicity. -- Highlights: ► We characterize a new in silico model to predict mutagenicity of drug impurities. ► The model predicts Salmonella mutagenicity and will be useful for safety assessment. ► We examine toxicity fingerprints and toxicophores of this Ames assay model. ► We compare these attributes to those found in drug impurities known to FDA/CDER. ► We validate the model and find it has a desired predictive performance.« less

Topological edge states and impurities: Manifestation in the local static and dynamical characteristics of dimerized quantum chains

NASA Astrophysics Data System (ADS)

Zvyagin, A. A.

2018-04-01

Based on the results of exact analytic calculations, we show that topological edge states and impurities in quantum dimerized chains manifest themselves in various local static and dynamical characteristics, which can be measured in experiments. In particular, topological edge states can be observed in the magnetic field behavior of the local magnetization or magnetic susceptibility of dimerized spin chains as jumps (for the magnetization) and features (for the static susceptibility) at zero field. In contrast, impurities reveal themselves in similar jumps and features, however, at nonzero values of the critical field. We also show that dynamical characteristics of dimerized quantum chains also manifest the features, related to the topological edge states and impurities. Those features, as a rule, can be seen more sharply than the manifestation of bulk extended states in, e.g., the dynamical local susceptibility. Such peculiarities can be observed in one-dimensional dimerized spin chains, e.g., in NMR experiments, or in various realizations of quantum dimerized chains in optical experiments.

The Moral Virtue of Authenticity: How Inauthenticity Produces Feelings of Immorality and Impurity.

PubMed

Gino, Francesca; Kouchaki, Maryam; Galinsky, Adam D

2015-07-01

The five experiments reported here demonstrate that authenticity is directly linked to morality. We found that experiencing inauthenticity, compared with authenticity, consistently led participants to feel more immoral and impure. This link from inauthenticity to feeling immoral produced an increased desire among participants to cleanse themselves and to engage in moral compensation by behaving prosocially. We established the role that impurity played in these effects through mediation and moderation. We found that inauthenticity-induced cleansing and compensatory helping were driven by heightened feelings of impurity rather than by the psychological discomfort of dissonance. Similarly, physically cleansing oneself eliminated the relationship between inauthenticity and prosocial compensation. Finally, we obtained additional evidence for discriminant validity: The observed effects on desire for cleansing were not driven by general negative experiences (i.e., failing a test) but were unique to experiences of inauthenticity. Our results establish that authenticity is a moral state--that being true to thine own self is experienced as a form of virtue. © The Author(s) 2015.

Impurity coupled to an artificial magnetic field in a Fermi gas in a ring trap

NASA Astrophysics Data System (ADS)

Ünal, F. Nur; Hetényi, B.; Oktel, M. Ã.-.

2015-05-01

The dynamics of a single impurity interacting with a many-particle background is one of the central problems of condensed-matter physics. Recent progress in ultracold-atom experiments makes it possible to control this dynamics by coupling an artificial gauge field specifically to the impurity. In this paper, we consider a narrow toroidal trap in which a Fermi gas is interacting with a single atom. We show that an external magnetic field coupled to the impurity is a versatile tool to probe the impurity dynamics. Using a Bethe ansatz, we calculate the eigenstates and corresponding energies exactly as a function of the flux through the trap. Adiabatic change of flux connects the ground state to excited states due to flux quantization. For repulsive interactions, the impurity disturbs the Fermi sea by dragging the fermions whose momentum matches the flux. This drag transfers momentum from the impurity to the background and increases the effective mass. The effective mass saturates to the total mass of the system for infinitely repulsive interactions. For attractive interactions, the drag again increases the effective mass which quickly saturates to twice the mass of a single particle as a dimer of the impurity and one fermion is formed. For excited states with momentum comparable to number of particles, effective mass shows a resonant behavior. We argue that standard tools in cold-atom experiments can be used to test these predictions.

Polymeric efficiency in remove impurities during cottonseed biodiesel production

NASA Astrophysics Data System (ADS)

Lin, H. L.; Liang, Y. H.; Yan, J.; Lin, H. D.; Espinosa, A. R.

2016-07-01

This paper describes a new process for developing biodiesel by polymer from crude cottonseed oil. The study was conducted to examine the effectiveness of the alkali transesterification-flocculation-sedimentation process on fast glycerol and other impurities in the separation from biodiesel by using quaternary polyamine-based cationic polymers SL2700 and polyacylamide cationic polymer SAL1100. The settling velocity of glycerol and other impurities in biodiesel was investigated through settling test experiments; the quality of the biodiesel was investigated by evaluating the viscosity and density. The results revealed that SL2700, SAL1100 and their combination dramatically improved the settling velocity of glycerol and other impurities materials than traditional method. SL 2700 with molecular weight of 0.2 million Da and charge density of 50% then plus SAL1100 with molecular weight of 11 million Da and charge density of 10% induced observable particle aggregation with the best settling performance.

Implementation of the reduced charge state method of calculating impurity transport

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

Crume, E.C. Jr.; Arnurius, D.E.

1982-07-01

A recent review article by Hirshman and Sigmar includes expressions needed to calculate the parallel friction coefficients, the essential ingredients of the plateau-Pfirsch-Schluter transport coefficients, using the method of reduced charge states. These expressions have been collected and an expanded notation introduced in some cases to facilitate differentiation between reduced charge state and full charge state quantities. A form of the Coulomb logarithm relevant to the method of reduced charge states is introduced. This method of calculating the f/sub ij//sup ab/ has been implemented in the impurity transport simulation code IMPTAR and has resulted in an overall reduction in computationmore » time of approximately 25% for a typical simulation of impurity transport in the Impurity Study Experiment (ISX-B). Results obtained using this treatment are almost identical to those obtained using an earlier approximate theory of Hirshman.« less

Ultrasoft x-ray imaging system for the National Spherical Torus Experiment

NASA Astrophysics Data System (ADS)

Stutman, D.; Finkenthal, M.; Soukhanovskii, V.; May, M. J.; Moos, H. W.; Kaita, R.

1999-01-01

A spectrally resolved ultrasoft x-ray imaging system, consisting of arrays of high resolution (<2 Å) and throughput (⩾tens of kHz) miniature monochromators, and based on multilayer mirrors and absolute photodiodes, is being designed for the National Spherical Torus Experiment. Initially, three poloidal arrays of diodes filtered for C 1s-np emission will be implemented for fast tomographic imaging of the colder start-up plasmas. Later on, mirrors tuned to the C Lyα emission will be added in order to enable the arrays to "see" the periphery through the hot core and to study magnetohydrodynamic activity and impurity transport in this region. We also discuss possible core diagnostics, based on tomographic imaging of the Lyα emission from the plume of recombined, low Z impurity ions left by neutral beams or fueling pellets. The arrays can also be used for radiated power measurements and to map the distribution of high Z impurities injected for transport studies. The performance of the proposed system is illustrated with results from test channels on the CDX-U spherical torus at Princeton Plasma Physics Laboratory.

Classical confinement and outward convection of impurity ions in the MST RFP

NASA Astrophysics Data System (ADS)

Kumar, S. T. A.; Den Hartog, D. J.; Mirnov, V. V.; Caspary, K. J.; Magee, R. M.; Brower, D. L.; Chapman, B. E.; Craig, D.; Ding, W. X.; Eilerman, S.; Fiksel, G.; Lin, L.; Nornberg, M.; Parke, E.; Reusch, J. A.; Sarff, J. S.

2012-05-01

Impurity ion dynamics measured with simultaneously high spatial and temporal resolution reveal classical ion transport in the reversed-field pinch. The boron, carbon, oxygen, and aluminum impurity ion density profiles are obtained in the Madison Symmetric Torus [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)] using a fast, active charge-exchange-recombination-spectroscopy diagnostic. Measurements are made during improved-confinement plasmas obtained using inductive control of tearing instability to mitigate stochastic transport. At the onset of the transition to improved confinement, the impurity ion density profile becomes hollow, with a slow decay in the core region concurrent with an increase in the outer region, implying an outward convection of impurities. Impurity transport from Coulomb collisions in the reversed-field pinch is classical for all collisionality regimes, and analysis shows that the observed hollow profile and outward convection can be explained by the classical temperature screening mechanism. The profile agrees well with classical expectations. Experiments performed with impurity pellet injection provide further evidence for classical impurity ion confinement.

Effect of high Z impurities on the ignition and Lawson conditions for a thermonuclear reactor

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

Meade, D.M.

1973-06-01

The recent advances in plasma heating and confinement using Tokamak devices have produced plasmas which approach thermonuclear conditions. Substantial amounts (0.1 to 1%) of partially stripped high Z impurities have been observed in these discharges. These high Z impurities (Fe,Mo,W) are presumably due to plasma bombardment of the limiter and vacuum chamber wall. Since the plasma energy will be increasing sharply in the next sequence of experiments from approx. =1kJ in ST tokamak to approx. =3MJ in PLT and up to approx. =100MJ in a feasibility experiment, the bombardment of the wall and limiter will become increasingly important. In thismore » paper, the effects of high Z impurities on the ignition and Lawson conditions for a DT reactor are calculated. 7 refs., 2 figs.« less

Classical impurity ion confinement in a toroidal magnetized fusion plasma.

PubMed

Kumar, S T A; Den Hartog, D J; Caspary, K J; Magee, R M; Mirnov, V V; Chapman, B E; Craig, D; Fiksel, G; Sarff, J S

2012-03-23

High-resolution measurements of impurity ion dynamics provide first-time evidence of classical ion confinement in a toroidal, magnetically confined plasma. The density profile evolution of fully stripped carbon is measured in MST reversed-field pinch plasmas with reduced magnetic turbulence to assess Coulomb-collisional transport without the neoclassical enhancement from particle drift effects. The impurity density profile evolves to a hollow shape, consistent with the temperature screening mechanism of classical transport. Corroborating methane pellet injection experiments expose the sensitivity of the impurity particle confinement time to the residual magnetic fluctuation amplitude.

Development of RP-HPLC, Stability Indicating Method for Degradation Products of Linagliptin in Presence of Metformin HCl by Applying 2 Level Factorial Design; and Identification of Impurity-VII, VIII and IX and Synthesis of Impurity-VII.

PubMed

Jadhav, Sushant B; Reddy, P Sunil; Narayanan, Kalyanaraman L; Bhosale, Popatrao N

2017-06-27

The novel reverse phase-high performance liquid chromatography (RP-HPLC), stability indicating method was developed for determination of linagliptin (LGP) and its related substances in linagliptin and metformin HCl (MET HCl) tablets by implementing design of experiment to understand the critical method parameters and their relation with critical method attributes; to ensure robustness of the method. The separation of nine specified impurities was achieved with a Zorbax SB-Aq 250 × 4.6 mm, 5 µm column, using gradient elution and a detector wavelength of 225 nm, and validated in accordance with International Conference on Harmonization (ICH) guidelines and found to be accurate, precise, reproducible, robust, and specific . The drug was found to be degrading extensively in heat, humidity, basic, and oxidation conditions and was forming degradation products during stability studies. After slight modification in the buffer and the column, the same method was used for liquid chromatography-mass spectrometry (LC-MS) and ultra-performance liquid chromatography -time-of-flight/mass spectrometry UPLC-TOF/MS analysis, to identify m/z and fragmentation of maximum unspecified degradation products i.e., Impurity-VII ( 7 ), Impurity-VIII ( 8 ), and Impurity-IX ( 9 ) formed during stability studies. Based on the results, a degradation pathway for the drug has been proposed and synthesis of Impurity-VII ( 7 ) is also discussed to ensure an in-depth understanding of LGP and its related degradation products and optimum performance during the lifetime of the product.

Effect of the screened Coulomb disorder on magneto-transport in Weyl semimetals

NASA Astrophysics Data System (ADS)

Ji, Xuan-Ting; Lu, Hai-Zhou; Zhu, Zhen-Gang; Su, Gang

2018-05-01

The observation of negative longitudinal magnetoresistivity (NLMR) in Weyl semimetals has gained strong support in recent experiments. It is believed that charged impurities play an important role in the measurement of NLMR. We thus employ a screened Coulomb disorder to model charged impurities and derive a general screening length depending on the magnetic field, chemical potential and temperature. We study the magneto-transport in a two-node Weyl semimetal in which the intra-valley scattering and the inter-valley scattering can be explored simultaneously. We also calculate the effect of the misalignment of the external electric field and the magnetic field on the longitudinal and transverse magnetoconductivities, recovering the experimental observations. We show that the former (latter) is suppressed (enhanced) sensitively with the density of the impurity. This feature makes it hard to observe the NLMR in experiments in the heavy doping case. These results may be exploited to explain the sample-dependent observation of NLMR and deepen our understanding of magneto-transport in Weyl semimetals.

Impurity-defect complexes in non-implanted aluminum

NASA Astrophysics Data System (ADS)

Pedersen, F. T.; Grann, H.; Weyer, G.

1986-02-01

The formation of impurity-defect complexes in ion-implanted aluminum has been studied in the temperature interval 100 400K. Radioactive119In isotopes have been implanted. Mössbauer spectra have been measured for the 24 keV γ-radiation emitted after the decay to119Sn. The spectra could be analysed satisfactorily with two lines, one of which is known to be due to substitutional Sn. A second line, which has a higher isomer shift and lower Debye temperature, is tentatively assigned to vacancy-associated Sn, formed by trapping of thermally mobile (multi-)vacancies. Comparison to similar DPAC experiments suggests that cubic Sn-V4 complexes are formed. Some indication (˜15%) for an athermal formation of impurity defects below 175K is obtained.

Quasiparticle Properties of a Mobile Impurity in a Bose-Einstein Condensate.

PubMed

Christensen, Rasmus Søgaard; Levinsen, Jesper; Bruun, Georg M

2015-10-16

We develop a systematic perturbation theory for the quasiparticle properties of a single impurity immersed in a Bose-Einstein condensate. Analytical results are derived for the impurity energy, effective mass, and residue to third order in the impurity-boson scattering length. The energy is shown to depend logarithmically on the scattering length to third order, whereas the residue and the effective mass are given by analytical power series. When the boson-boson scattering length equals the boson-impurity scattering length, the energy has the same structure as that of a weakly interacting Bose gas, including terms of the Lee-Huang-Yang and fourth order logarithmic form. Our results, which cannot be obtained within the canonical Fröhlich model of an impurity interacting with phonons, provide valuable benchmarks for many-body theories and for experiments.

Impact of the Injection Protocol on an Impurity's Stationary State

NASA Astrophysics Data System (ADS)

Gamayun, Oleksandr; Lychkovskiy, Oleg; Burovski, Evgeni; Malcomson, Matthew; Cheianov, Vadim V.; Zvonarev, Mikhail B.

2018-06-01

We examine stationary-state properties of an impurity particle injected into a one-dimensional quantum gas. We show that the value of the impurity's end velocity lies between zero and the speed of sound in the gas and is determined by the injection protocol. This way, the impurity's constant motion is a dynamically emergent phenomenon whose description goes beyond accounting for the kinematic constraints of the Landau approach to superfluidity. We provide exact analytic results in the thermodynamic limit and perform finite-size numerical simulations to demonstrate that the predicted phenomena are within the reach of the ultracold gas experiments.

Quantifying Main Trends in Lysozyme Nucleation: The Effect of Precipitant Concentration and Impurities

NASA Technical Reports Server (NTRS)

Burke, Michael W.; Judge, Russell A.; Pusey, Marc L.; Rose, M. Franklin (Technical Monitor)

2000-01-01

Full factorial experiment design incorporating multi-linear regression analysis of the experimental data allows the main trends and effects to be quickly identified while using only a limited number of experiments. These techniques were used to identify the effect of precipitant concentration and the presence of an impurity, the physiological lysozyme dimer, on the nucleation rate and crystal dimensions of the tetragonal form of chicken egg white lysozyme. Increasing precipitant concentration was found to decrease crystal numbers, the magnitude of this effect also depending on the supersaturation. The presence of the dimer generally increased nucleation. The crystal axial ratio decreased with increasing precipitant concentration independent of impurity.

Spatially resolved NMR spectra for the Swiss cheese model in heavy fermion PuCoGa5 superconductor

NASA Astrophysics Data System (ADS)

Das, Tanmoy; Zhu, Jian-Xin; Balatsky, A. V.; Graf, M. J.

2011-03-01

Spatially resolved NMR experiments, which probe the local electronic excitations, play a vital role for studying the pairing symmetry of unconventional superconductors. Here we calculate the spatial modulation of the NMR spin-lattice relaxation rate (1/T1) for the Swiss cheese model as a function of impurity concentration in PuCoGa5 superconductor. The local suppression of the superconducting order parameter due to impurities is related to the number of holes in the Swiss cheese model. Our results indicate that Friedel-like oscillations,as seen in the local-density of states near an impurity, are also present in the behavior of 1/T1 as one moves away from the impurity site. We demonstrate that the gap nodes, which are filled by disorder, can be probed by NMR through the local information encoded in the spectra. The advantage of spatially resolved NMR compared to STM measurements is that the former probe is not sensitive to surface states. Work is supported by US DOE.

Impurity behavior during ion-Bernstein wave heating in PBX-M

NASA Astrophysics Data System (ADS)

Isler, R. C.; Post-Zwicker, A. P.; Paul, S. F.; Tighe, W.; Ono, M.; Leblanc, B. P.; Bell, R.; Kugel, H. W.; Kaita, R.

1994-07-01

Ion-Bernstein-wave heating (IBWH) has been tested in several tokamaks. In some cases the results have been quite positive, producing temperature increases and also improving both energy and particle confinement times, whereas in others, no distinctive changes were observed. Most recently, IBWH has been utilized in the Princeton Beta Experiment-Modified (PBX-M) where the long-range goal is the achievement of operation in the second stable region by current and pressure profile control. Investigations have been performed in this machine using IBWH as the sole source of auxiliary power or using IBWH in conjunction with neutral-beam injection (NBI) or with lower-hybrid current drive (LHCD). Impurity studies seem particularly important for IBWH since not only have influxes often been observed to increase, but the global impurity confinement time has also been shown to lengthen as the confinement of the working gas improved. The authors present here a set of characteristic experimental results regarding the impurity behavior in PBX-M; in general, these are consonant with previous observations in other tokamaks.

Morphological transitions in nanoscale patterns produced by concurrent ion sputtering and impurity co-deposition

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

Bradley, R. Mark

2016-04-07

We modify the theory of nanoscale patterns produced by ion bombardment with concurrent impurity deposition to take into account the effect that the near-surface impurities have on the collision cascades. As the impurity concentration is increased, the resulting theory successively yields a flat surface, a rippled surface with its wavevector along the projected direction of ion incidence, and a rippled surface with its wavevector rotated by 90°. Exactly the same morphological transitions were observed in recent experiments in which silicon was bombarded with an argon ion beam and gold was co-deposited [Moon et al., e-print arXiv:1601.02534].

Mixed valent metals

NASA Astrophysics Data System (ADS)

Riseborough, P. S.; Lawrence, J. M.

2016-08-01

We review the theory of mixed-valent metals and make comparison with experiments. A single-impurity description of the mixed-valent state is discussed alongside the description of the nearly-integer valent or Kondo limit. The degeneracy N of the f-shell plays an important role in the description of the low-temperature Fermi-liquid state. In particular, for large N, there is a rapid cross-over between the mixed-valent and the Kondo limit when the number of f electrons is changed. We discuss the limitations on the application of the single-impurity description to concentrated compounds such as those caused by the saturation of the Kondo effect and those due to the presence of magnetic interactions between the impurities. This discussion is followed by a description of a periodic lattice of mixed-valent ions, including the role of the degeneracy N. The article concludes with a comparison of theory and experiment. Topics covered include the single-impurity Anderson model, Luttinger’s theorem, the Friedel sum rule, the Schrieffer-Wolff transformation, the single-impurity Kondo model, Kondo screening, the Wilson ratio, local Fermi-liquids, Fermi-liquid sum rules, the Noziéres exhaustion principle, Doniach’s diagram, the Anderson lattice model, the Slave-Boson method, etc.

Mixed valent metals

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

Riseborough, P. S.; Lawrence, Jon M.

Here, we review the theory of mixed-valent metals and make comparison with experiments. A single-impurity description of the mixed-valent state is discussed alongside the description of the nearly-integer valent or Kondo limit. The degeneracy N of the f-shell plays an important role in the description of the low-temperature Fermi-liquid state. In particular, for large N, there is a rapid cross-over between the mixed-valent and the Kondo limit when the number of f electrons is changed. We discuss the limitations on the application of the single-impurity description to concentrated compounds such as those caused by the saturation of the Kondo effectmore » and those due to the presence of magnetic interactions between the impurities. This discussion is followed by a description of a periodic lattice of mixed-valent ions, including the role of the degeneracy N. The article concludes with a comparison of theory and experiment. Topics covered include the single-impurity Anderson model, Luttinger's theorem, the Friedel sum rule, the Schrieffer–Wolff transformation, the single-impurity Kondo model, Kondo screening, the Wilson ratio, local Fermi-liquids, Fermi-liquid sum rules, the Nozieres exhaustion principle, Doniach's diagram, the Anderson lattice model, the Slave-Boson method, etc.« less

Mixed valent metals

DOE PAGES

Riseborough, P. S.; Lawrence, Jon M.

2016-07-04

Here, we review the theory of mixed-valent metals and make comparison with experiments. A single-impurity description of the mixed-valent state is discussed alongside the description of the nearly-integer valent or Kondo limit. The degeneracy N of the f-shell plays an important role in the description of the low-temperature Fermi-liquid state. In particular, for large N, there is a rapid cross-over between the mixed-valent and the Kondo limit when the number of f electrons is changed. We discuss the limitations on the application of the single-impurity description to concentrated compounds such as those caused by the saturation of the Kondo effectmore » and those due to the presence of magnetic interactions between the impurities. This discussion is followed by a description of a periodic lattice of mixed-valent ions, including the role of the degeneracy N. The article concludes with a comparison of theory and experiment. Topics covered include the single-impurity Anderson model, Luttinger's theorem, the Friedel sum rule, the Schrieffer–Wolff transformation, the single-impurity Kondo model, Kondo screening, the Wilson ratio, local Fermi-liquids, Fermi-liquid sum rules, the Nozieres exhaustion principle, Doniach's diagram, the Anderson lattice model, the Slave-Boson method, etc.« less

Three-dimensional simulation of H-mode plasmas with localized divertor impurity injection on Alcator C-Mod using the edge transport code EMC3-EIRENE

DOE PAGES

Lore, Jeremy D.; Reinke, M. L.; Brunner, D.; ...

2015-04-28

We study experiments in Alcator C-Mod to assess the level of toroidal asymmetry in divertor conditions resulting from poloidally and toroidally localized extrinsic impurity gas seeding show a weak toroidal peaking (~1.1) in divertor electron temperatures for high-power enhanced D-alpha H-modeplasmas. This is in contrast to similar experiments in Ohmically heated L-modeplasmas, which showed a clear toroidal modulation in the divertor electron temperature. Modeling of these experiments using the 3D edge transport code EMC3-EIRENE [Y. Feng et al., J. Nucl. Mater. 241, 930 (1997)] qualitatively reproduces these trends, and indicates that the different response in the simulations is due tomore » the ionization location of the injected nitrogen. Low electron temperatures in the private flux region (PFR) in L-mode result in a PFR plasma that is nearly transparent to neutral nitrogen, while in H-mode the impurities are ionized in close proximity to the injection location, with this latter case yielding a largely axisymmetric radiation pattern in the scrape-off-layer. In conclusion, the consequences for the ITER gas injection system are discussed. Quantitative agreement with the experiment is lacking in some areas, suggesting potential areas for improving the physics model in EMC3-EIRENE.« less

Identification of unknown impurity of azelaic acid in liposomal formulation assessed by HPLC-ELSD, GC-FID, and GC-MS.

PubMed

Han, Stanisław; Karłowicz-Bodalska, Katarzyna; Potaczek, Piotr; Wójcik, Adam; Ozimek, Lukasz; Szura, Dorota; Musiał, Witold

2014-02-01

The identification of new contaminants is critical in the development of new medicinal products. Many impurities, such as pentanedioic acid, hexanedioic acid, heptanedioic acid, octanedioic acid, decanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, and tetradecanedioic acid, have been identified in samples of azelaic acid. The aim of this study was to identify impurities observed during the stability tests of a new liposomal dosage form of azelaic acid that is composed of phosphatidylcholine and a mixture of ethyl alcohol and water, using high-performance liquid chromatography with evaporative light-scattering detector (HPLC-ELSD), gas chromatography-flame ionisation detection (GC-FID), and gas chromatography-mass spectrometry (GC-MS) methods. During the research and development of a new liposomal formulation of azelaic acid, we developed a method for determining the contamination of azelaic acid using HPLC-ELSD. During our analytical tests, we identified a previously unknown impurity of a liposomal preparation of azelaic acid that appeared in the liposomal formulation of azelaic acid during preliminary stability studies. The procedure led to the conclusion that the impurity was caused by the reaction of azelaic acid with one of the excipients that was applied in the product. The impurity was finally identified as an ethyl monoester of azelaic acid. The identification procedure of this compound was carried out in a series of experiments comparing the chromatograms that were obtained via the following chromatographic methods: HPLC-ELSD, GC-FID, and GC-MS. The final identification of the compound was carried out by GC with MS.

Design of aqueous two-phase systems for purification of hyaluronic acid produced by metabolically engineered Lactococcus lactis.

PubMed

Rajendran, Vivek; Puvendran, Kirubhakaran; Guru, Bharath Raja; Jayaraman, Guhan

2016-02-01

Hyaluronic acid has a wide range of biomedical applications and its commercial value is highly dependent on its purity and molecular weight. This study highlights the utility of aqueous two-phase separation as a primary recovery step for hyaluronic acid and for removal of major protein impurities from fermentation broths. Metabolically engineered cultures of a lactate dehydrogenase mutant strain of Lactococcus lactis (L. lactis NZ9020) were used to produce high-molecular-weight hyaluronic acid. The cell-free fermentation broth was partially purified using a polyethylene glycol/potassium phosphate system, resulting in nearly 100% recovery of hyaluronic acid in the salt-rich bottom phase in all the aqueous two-phase separation experiments. These experiments were optimized for maximum removal of protein impurities in the polyethylene glycol rich top phase. The removal of protein impurities resulted in substantial reduction of membrane fouling in the subsequent diafiltration process, carried out with a 300 kDa polyether sulfone membrane. This step resulted in considerable purification of hyaluronic acid, without any loss in recovery and molecular weight. Diafiltration was followed by an adsorption step to remove minor impurities and achieve nearly 100% purity. The final hyaluronic acid product was characterized by Fourier-transform IR and NMR spectroscopy, confirming its purity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tunneling interstitial impurity in iron-chalcogenide-based superconductors

NASA Astrophysics Data System (ADS)

Huang, Huaixiang; Zhang, Degang; Gao, Yi; Ren, Wei; Ting, C. S.

2016-02-01

A pronounced local in-gap zero-energy bound state (ZBS) has been observed by recent scanning tunneling microscopy experiments on the interstitial Fe impurity (IFI) and its nearest-neighboring sites in an FeTe0.5Se0.5 superconducting (SC) compound. By introducing an impurity mechanism, the so-called tunneling impurity, and based on the Bogoliubov-de Gennes equations, we investigate the low-lying energy states of the IFI and the underlying Fe plane. The calculations are performed in the presence as well as in the absence of a magnetic field. We find the IFI-induced ZBS does not shift or split in a magnetic field as long as the tunneling parameter between the IFI and the Fe plane is sufficiently small and the Fe plane is deep in the SC state. Our results are in good agreement with experiments. We also show that in the underdoped cases, modulation of the spin density wave or charge density wave will suppress the intensity of the ZBS on the Fe plane in a vortex state.

Magnetic impurity effect on charge and magnetic order in doped La1.5Ca0.5CoO4

NASA Astrophysics Data System (ADS)

Horigane, K.; Hiraka, H.; Tomiyasu, K.; Ohoyama, K.; Louca, D.; Yamada, K.

2012-02-01

Neutron scattering experiments were performed on single crystals of magnetic impurity doped cobalt oxides La1.5Ca0.5CoO4 to characterize the charge and spin orders. We newly found contrasting impurity effects. Two types of magnetic peaks are observed at q = (0.5,0,L) with L = half-integer and integer in La1.5Ca0.5CoO4, while magnetic peak at L = half-integer (integer) was only observed in Mn (Fe)-substituted sample. Although Mn and Fe impurities degrade charge and magnetic order, Cr impurity stabilizes the ordering at x = 0.5. Based on the crystal structural analysis of Cr doped sample, we found that the excess oxygen and change of octahedron around Co3+ were realized in Cr doped sample.

Cobalt adatoms on graphene: Effects of anisotropies on the correlated electronic structure

NASA Astrophysics Data System (ADS)

Mozara, R.; Valentyuk, M.; Krivenko, I.; Şaşıoǧlu, E.; Kolorenč, J.; Lichtenstein, A. I.

2018-02-01

Impurities on surfaces experience a geometric symmetry breaking induced not only by the on-site crystal-field splitting and the orbital-dependent hybridization, but also by different screening of the Coulomb interaction in different directions. We present a many-body study of the Anderson impurity model representing a Co adatom on graphene, taking into account all anisotropies of the effective Coulomb interaction, which we obtained by the constrained random-phase approximation. The most pronounced differences are naturally displayed by the many-body self-energy projected onto the single-particle states. For the solution of the Anderson impurity model and analytical continuation of the Matsubara data, we employed new implementations of the continuous-time hybridization expansion quantum Monte Carlo and the stochastic optimization method, and we verified the results in parallel with the exact diagonalization method.

Imaging study of using radiopharmaceuticals labeled with cyclotron-produced 99mTc.

PubMed

Hou, X; Tanguay, J; Vuckovic, M; Buckley, K; Schaffer, P; Bénard, F; Ruth, T J; Celler, A

2016-12-07

Cyclotron-produced 99m Tc (CPTc) has been recognized as an attractive and practical substitution of reactor/generator based 99m Tc. However, the small amount of 92-98 Mo in the irradiation of enriched 100 Mo could lead to the production of other radioactive technetium isotopes (Tc-impurities) which cannot be chemically separated. Thus, these impurities could contribute to patient dose and affect image quality. The potential radiation dose caused by these Tc-impurities produced using different targets, irradiation conditions, and corresponding to different injection times have been investigated, leading us to create dose-based limits of these parameters for producing clinically acceptable CPTc. However, image quality has been not considered. The aim of the present work is to provide a comprehensive and quantitative analysis of image quality for CPTc. The impact of Tc-impurities in CPTc on image resolution, background noise, and contrast is investigated by performing both Monte-Carlo simulations and phantom experiments. Various targets, irradiation, and acquisition conditions are employed for investigating the image-based limits of CPTc production parameters. Additionally, the relationship between patient dose and image quality of CPTc samples is studied. Only those samples which meet both dose- and image-based limits should be accepted in future clinical studies.

Imaging study of using radiopharmaceuticals labeled with cyclotron-produced 99mTc

NASA Astrophysics Data System (ADS)

Hou, X.; Tanguay, J.; Vuckovic, M.; Buckley, K.; Schaffer, P.; Bénard, F.; Ruth, T. J.; Celler, A.

2016-12-01

Cyclotron-produced 99mTc (CPTc) has been recognized as an attractive and practical substitution of reactor/generator based 99mTc. However, the small amount of 92-98Mo in the irradiation of enriched 100Mo could lead to the production of other radioactive technetium isotopes (Tc-impurities) which cannot be chemically separated. Thus, these impurities could contribute to patient dose and affect image quality. The potential radiation dose caused by these Tc-impurities produced using different targets, irradiation conditions, and corresponding to different injection times have been investigated, leading us to create dose-based limits of these parameters for producing clinically acceptable CPTc. However, image quality has been not considered. The aim of the present work is to provide a comprehensive and quantitative analysis of image quality for CPTc. The impact of Tc-impurities in CPTc on image resolution, background noise, and contrast is investigated by performing both Monte-Carlo simulations and phantom experiments. Various targets, irradiation, and acquisition conditions are employed for investigating the image-based limits of CPTc production parameters. Additionally, the relationship between patient dose and image quality of CPTc samples is studied. Only those samples which meet both dose- and image-based limits should be accepted in future clinical studies.

Enhanced production of acarbose and concurrently reduced formation of impurity c by addition of validamine in fermentation of Actinoplanes utahensis ZJB-08196.

PubMed

Xue, Ya-Ping; Qin, Jun-Wei; Wang, Ya-Jun; Wang, Yuan-Shan; Zheng, Yu-Guo

2013-01-01

Commercial production of acarbose is exclusively via done microbial fermentation with strains from the genera of Actinoplanes. The addition of C7N-aminocyclitols for enhanced production of acarbose and concurrently reduced formation of impurity C by cultivation of A. utahensis ZJB-08196 in 500-mL shake flasks was investigated, and validamine was found to be the most effective strategy. Under the optimal conditions of validamine addition, acarbose titer was increased from 3560 ± 128 mg/L to 4950 ± 156 mg/L, and impurity C concentration was concurrently decreased from 289 ± 24 mg/L to 107 ± 29 mg/L in batch fermentation after 168 h of cultivation. A further fed-batch experiment coupled with the addition of validamine (20 mg/L) in the fermentation medium prior to inoculation was designed to enhance the production of acarbose. When twice feedings of a mixture of 6 g/L glucose, 14 g/L maltose, and 9 g/L soybean flour were performed at 72 h and 96 h, acarbose titer reached 6606 ± 103 mg/L and impurity C concentration was only 212 ± 12 mg/L at 168 h of cultivation. Acarbose titer and proportion of acarbose/impurity C increased by 85.6% and 152.9% when compared with control experiments. This work demonstrates for the first time that validamine addition is a simple and effective strategy for increasing acarbose production and reducing impurity C formation.

Micellar Packing in Aqueous Solutions of As-Received and Pure Pluronic Block Copolymers

NASA Astrophysics Data System (ADS)

Ryu, Chang; Park, Han Jin

2013-03-01

Pluronic block copolymers (Pluronics) are produced on a commercial scale to enable wide range of novel applications from emulsification and colloidal stabilization as nonionic surfactants. While the Pluronic block copolymers offer the advantages of being readily available for such applications, it contains non-micellizable low molecular weight (MW) impurities that would interfere with the self-assembly and micellar packing of PEO-PPO-PEO triblock copolymers in aqueous solutions. The impacts of the low MW impurities will be discussed on the micellar packing of Pluronics F108 and F127 solutions, which form BCC and FCC. While as-received Pluronic samples typically contain about 20 wt.% low MW impurities, we were able to reduce the impurity level to less than 2 wt.% using our large scale purification technique. Comparative studies on small angle x-ray scattering (SAXS) experiments on as-received and purified Pluronics solutions revealed that the contents of triblock copolymers in solutions essentially governs the inter-micellar distance of Pluronic cubic structures. A universal relationship between triblock copolymer concentration and SAXS-based domain spacing has been finally discussed. Funding from Agency for Defense Development, Korea.

VUV/XUV measurements of impurity emission in plasmas with liquid lithium surfaces on LTX [VUV/XUV measurements of low recycling plasmas with liquid lithium surfaces on LTX

DOE PAGES

Tritz, Kevin; Bell, Ronald E.; Beiersdorfer, Peter; ...

2014-11-12

The VUV/XUV spectrum has been measured on the Lithium Tokamak eXperiment (LTX) using a transmission grating imaging spectrometer (TGIS) coupled to a direct-detection x-ray charge-coupled device camera. TGIS data show significant changes in the ratios between the lithium and oxygen impurity line emission during discharges with varying lithium wall conditions. Lithium coatings that have been passivated by lengthy exposure to significant levels of impurities contribute to a large O/Li ratio measured during LTX plasma discharges. Furthermore, previous results have indicated that a passivated lithium film on the plasma facing components will function as a stronger impurity source when in themore » form of a hot liquid layer compared to a solid lithium layer. However, recent TGIS measurements of plasma discharges in LTX with hot stainless steel boundary shells and a fresh liquid lithium coating show lower O/Li impurity line ratios when compared to discharges with a solid lithium film on cool shells. In conclusion, these new measurements help elucidate the somewhat contradictory results of the effects of solid and liquid lithium on plasma confinement observed in previous experiments.« less

Influence of Alumina Reaction Tube Impurities on the Oxidation of Chemically-Vapor-Deposited Silicon Carbide

NASA Technical Reports Server (NTRS)

Opila, Elizabeth

1995-01-01

Pure coupons of chemically vapor deposited (CVD) SiC were oxidized for 100 h in dry flowing oxygen at 1300 C. The oxidation kinetics were monitored using thermogravimetry (TGA). The experiments were first performed using high-purity alumina reaction tubes. The experiments were then repeated using fused quartz reaction tubes. Differences in oxidation kinetics, scale composition, and scale morphology were observed. These differences were attributed to impurities in the alumina tubes. Investigators interested in high-temperature oxidation of silica formers should be aware that high-purity alumina can have significant effects on experiment results.

Kinetic shear Alfvén instability in the presence of impurity ions in tokamak plasmas

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

Lu, Gaimin; Shen, Y.; Xie, T.

2013-10-15

The effects of impurity ions on the kinetic shear Alfvén (KSA) instability in tokamak plasmas are investigated by numerically solving the integral equations for the KSA eigenmode in the toroidal geometry. The kinetic effects of hydrogen and impurity ions, including transit motion, finite ion Larmor radius, and finite-orbit-width, are taken into account. Toroidicity induced linear mode coupling is included through the ballooning-mode representation. Here, the effects of carbon, oxygen, and tungsten ions on the KSA instability in toroidal plasmas are investigated. It is found that, depending on the concentration and density profile of the impurity ions, the latter can bemore » either stabilizing or destabilizing for the KSA modes. The results here confirm the importance of impurity ions in tokamak experiments and should be useful for analyzing experimental data as well as for understanding anomalous transport and control of tokamak plasmas.« less

X-ray crystal spectrometer upgrade for ITER-like wall experiments at JETa)

NASA Astrophysics Data System (ADS)

Shumack, A. E.; Rzadkiewicz, J.; Chernyshova, M.; Jakubowska, K.; Scholz, M.; Byszuk, A.; Cieszewski, R.; Czarski, T.; Dominik, W.; Karpinski, L.; Kasprowicz, G.; Pozniak, K.; Wojenski, A.; Zabolotny, W.; Conway, N. J.; Dalley, S.; Figueiredo, J.; Nakano, T.; Tyrrell, S.; Zastrow, K.-D.; Zoita, V.

2014-11-01

The high resolution X-Ray crystal spectrometer at the JET tokamak has been upgraded with the main goal of measuring the tungsten impurity concentration. This is important for understanding impurity accumulation in the plasma after installation of the JET ITER-like wall (main chamber: Be, divertor: W). This contribution provides details of the upgraded spectrometer with a focus on the aspects important for spectral analysis and plasma parameter calculation. In particular, we describe the determination of the spectrometer sensitivity: important for impurity concentration determination.

X-ray crystal spectrometer upgrade for ITER-like wall experiments at JET.

PubMed

Shumack, A E; Rzadkiewicz, J; Chernyshova, M; Jakubowska, K; Scholz, M; Byszuk, A; Cieszewski, R; Czarski, T; Dominik, W; Karpinski, L; Kasprowicz, G; Pozniak, K; Wojenski, A; Zabolotny, W; Conway, N J; Dalley, S; Figueiredo, J; Nakano, T; Tyrrell, S; Zastrow, K-D; Zoita, V

2014-11-01

The high resolution X-Ray crystal spectrometer at the JET tokamak has been upgraded with the main goal of measuring the tungsten impurity concentration. This is important for understanding impurity accumulation in the plasma after installation of the JET ITER-like wall (main chamber: Be, divertor: W). This contribution provides details of the upgraded spectrometer with a focus on the aspects important for spectral analysis and plasma parameter calculation. In particular, we describe the determination of the spectrometer sensitivity: important for impurity concentration determination.

Nonequilibrium Quasiparticle Distribution Induced by Kondo Defects

NASA Astrophysics Data System (ADS)

Kroha, J.; Zawadowski, A.

2002-04-01

It is shown that in resistive nanowires out of equilibrium containing either single- or two-channel Kondo impurities the distribution function f(E,U) obeys scaling behavior in terms of the quasiparticle energy E and the bias voltage U. The numerically calculated f(E,U) curves explain quantitatively recent experiments on Cu and Au nanowires. The systematics of the impurity concentration cimp extracted from the comparison between theory and results on various Cu and Au samples strongly suggests that in these systems the scaling arises from magnetic Kondo impurities.

Two-dimensional AXUV-based radiated power density diagnostics on NSTX-Ua)

NASA Astrophysics Data System (ADS)

Faust, I.; Delgado-Aparicio, L.; Bell, R. E.; Tritz, K.; Diallo, A.; Gerhardt, S. P.; LeBlanc, B.; Kozub, T. A.; Parker, R. R.; Stratton, B. C.

2014-11-01

A new set of radiated-power-density diagnostics for the National Spherical Torus Experiment Upgrade (NSTX-U) tokamak have been designed to measure the two-dimensional poloidal structure of the total photon emissivity profile in order to perform power balance, impurity transport, and magnetohydrodynamic studies. Multiple AXUV-diode based pinhole cameras will be installed in the same toroidal angle at various poloidal locations. The local emissivity will be obtained from several types of tomographic reconstructions. The layout and response expected for the new radially viewing poloidal arrays will be shown for different impurity concentrations to characterize the diagnostic sensitivity. The radiated power profile inverted from the array data will also be used for estimates of power losses during transitions from various divertor configurations in NSTX-U. The effect of in-out and top/bottom asymmetries in the core radiation from high-Z impurities will be addressed.

Two-dimensional AXUV-based radiated power density diagnostics on NSTX-U.

PubMed

Faust, I; Delgado-Aparicio, L; Bell, R E; Tritz, K; Diallo, A; Gerhardt, S P; LeBlanc, B; Kozub, T A; Parker, R R; Stratton, B C

2014-11-01

A new set of radiated-power-density diagnostics for the National Spherical Torus Experiment Upgrade (NSTX-U) tokamak have been designed to measure the two-dimensional poloidal structure of the total photon emissivity profile in order to perform power balance, impurity transport, and magnetohydrodynamic studies. Multiple AXUV-diode based pinhole cameras will be installed in the same toroidal angle at various poloidal locations. The local emissivity will be obtained from several types of tomographic reconstructions. The layout and response expected for the new radially viewing poloidal arrays will be shown for different impurity concentrations to characterize the diagnostic sensitivity. The radiated power profile inverted from the array data will also be used for estimates of power losses during transitions from various divertor configurations in NSTX-U. The effect of in-out and top/bottom asymmetries in the core radiation from high-Z impurities will be addressed.

Local destruction of superconductivity by non-magnetic impurities in mesoscopic iron-based superconductors

NASA Astrophysics Data System (ADS)

Li, Jun; Ji, Min; Schwarz, Tobias; Ke, Xiaoxing; van Tendeloo, Gustaaf; Yuan, Jie; Pereira, Paulo J.; Huang, Ya; Zhang, Gufei; Feng, Hai-Luke; Yuan, Ya-Hua; Hatano, Takeshi; Kleiner, Reinhold; Koelle, Dieter; Chibotaru, Liviu F.; Yamaura, Kazunari; Wang, Hua-Bing; Wu, Pei-Heng; Takayama-Muromachi, Eiji; Vanacken, Johan; Moshchalkov, Victor V.

2015-07-01

The determination of the pairing symmetry is one of the most crucial issues for the iron-based superconductors, for which various scenarios are discussed controversially. Non-magnetic impurity substitution is one of the most promising approaches to address the issue, because the pair-breaking mechanism from the non-magnetic impurities should be different for various models. Previous substitution experiments demonstrated that the non-magnetic zinc can suppress the superconductivity of various iron-based superconductors. Here we demonstrate the local destruction of superconductivity by non-magnetic zinc impurities in Ba0.5K0.5Fe2As2 by exploring phase-slip phenomena in a mesoscopic structure with 119 × 102 nm2 cross-section. The impurities suppress superconductivity in a three-dimensional `Swiss cheese'-like pattern with in-plane and out-of-plane characteristic lengths slightly below ~1.34 nm. This causes the superconducting order parameter to vary along abundant narrow channels with effective cross-section of a few square nanometres. The local destruction of superconductivity can be related to Cooper pair breaking by non-magnetic impurities.

Local destruction of superconductivity by non-magnetic impurities in mesoscopic iron-based superconductors

PubMed Central

Li, Jun; Ji, Min; Schwarz, Tobias; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Yuan, Jie; Pereira, Paulo J.; Huang, Ya; Zhang, Gufei; Feng, Hai-Luke; Yuan, Ya-Hua; Hatano, Takeshi; Kleiner, Reinhold; Koelle, Dieter; Chibotaru, Liviu F.; Yamaura, Kazunari; Wang, Hua-Bing; Wu, Pei-Heng; Takayama-Muromachi, Eiji; Vanacken, Johan; Moshchalkov, Victor V.

2015-01-01

The determination of the pairing symmetry is one of the most crucial issues for the iron-based superconductors, for which various scenarios are discussed controversially. Non-magnetic impurity substitution is one of the most promising approaches to address the issue, because the pair-breaking mechanism from the non-magnetic impurities should be different for various models. Previous substitution experiments demonstrated that the non-magnetic zinc can suppress the superconductivity of various iron-based superconductors. Here we demonstrate the local destruction of superconductivity by non-magnetic zinc impurities in Ba0.5K0.5Fe2As2 by exploring phase-slip phenomena in a mesoscopic structure with 119 × 102 nm2 cross-section. The impurities suppress superconductivity in a three-dimensional ‘Swiss cheese'-like pattern with in-plane and out-of-plane characteristic lengths slightly below ∼1.34 nm. This causes the superconducting order parameter to vary along abundant narrow channels with effective cross-section of a few square nanometres. The local destruction of superconductivity can be related to Cooper pair breaking by non-magnetic impurities. PMID:26139568

Local destruction of superconductivity by non-magnetic impurities in mesoscopic iron-based superconductors.

PubMed

Li, Jun; Ji, Min; Schwarz, Tobias; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Yuan, Jie; Pereira, Paulo J; Huang, Ya; Zhang, Gufei; Feng, Hai-Luke; Yuan, Ya-Hua; Hatano, Takeshi; Kleiner, Reinhold; Koelle, Dieter; Chibotaru, Liviu F; Yamaura, Kazunari; Wang, Hua-Bing; Wu, Pei-Heng; Takayama-Muromachi, Eiji; Vanacken, Johan; Moshchalkov, Victor V

2015-07-03

The determination of the pairing symmetry is one of the most crucial issues for the iron-based superconductors, for which various scenarios are discussed controversially. Non-magnetic impurity substitution is one of the most promising approaches to address the issue, because the pair-breaking mechanism from the non-magnetic impurities should be different for various models. Previous substitution experiments demonstrated that the non-magnetic zinc can suppress the superconductivity of various iron-based superconductors. Here we demonstrate the local destruction of superconductivity by non-magnetic zinc impurities in Ba0.5K0.5Fe2As2 by exploring phase-slip phenomena in a mesoscopic structure with 119 × 102 nm(2) cross-section. The impurities suppress superconductivity in a three-dimensional 'Swiss cheese'-like pattern with in-plane and out-of-plane characteristic lengths slightly below ∼1.34 nm. This causes the superconducting order parameter to vary along abundant narrow channels with effective cross-section of a few square nanometres. The local destruction of superconductivity can be related to Cooper pair breaking by non-magnetic impurities.

Ground Based Program for the Physical Analysis of Macromolecular Crystal Growth

NASA Technical Reports Server (NTRS)

Malkin, Alexander J.

1998-01-01

During the past year we have focused on application of in situ Atomic Force Microscopy (AFM) for studies of the growth mechanisms and kinetics of crystallization for different macromolecular systems. Mechanisms of macrostep formation and their decay, which are important in understanding of defect formation, were studied on the surfaces of thaumatin, catalase, canavalin and lysozyme crystals. Experiments revealed that step bunching on crystalline surfaces occurred either due to two- or three-dimensional nucleation on the terraces of vicinal slopes or as a result of uneven step generation by complex dislocation sources. No step bunching arising from interaction of individual steps in the course of the experiment was observed. The molecular structure of the growth steps for thaumatin and lipase crystals were deduced. It was further shown that growth step advance occurs by incorporation of single protein molecules. In singular directions growth steps move by one-dimensional nucleation on step edges followed by lateral growth. One-dimensional nuclei have different sizes, less then a single unit cell, varying for different directions of step movement. There is no roughness due to thermal fluctuations, and each protein molecule which incorporated into the step remained. Growth kinetics for catalase crystals was investigated over wide supersaturation ranges. Strong directional kinetic anisotropy in the tangential step growth rates in different directions was seen. The influence of impurities on growth kinetics and cessation of macromolecular crystals was studied. Thus, for catalase, in addition to pronounced impurity effects on the kinetics of crystallization, we were also able to directly observe adsorption of some impurities. At low supersaturation we repeatedly observed filaments which formed from impurity molecules sedimenting on the surfaces. Similar filaments were observed on the surfaces of thaumatin, canavalin and STMV crystals as well, but the frequency was low compared with catalase crystallization. Cessation of growth of xylanase and lysozyme crystals was also observed and appeared to be a consequence of the formation of dense impurity adsorption layers. Attachment: "An in situ AFM investigation of catalase crystallization", "Atomic force microscopy studies of living cells: visualization of motility, division, aggregation, transformation, and apoptosis", AFM studies on mechanisms of nucleation and growth of macromolecular crystals", and "In situ atomic force microscopy studies of surface morphology, growth kinetics, defect structure and dissolution in macromolecular crystallization".

Material Surface Characteristics and Plasma Performance in the Lithium Tokamak Experiment

NASA Astrophysics Data System (ADS)

Lucia, Matthew James

The performance of a tokamak plasma and the characteristics of the surrounding plasma facing component (PFC) material surfaces strongly influence each other. Despite this relationship, tokamak plasma physics has historically been studied more thoroughly than PFC surface physics. The disparity is particularly evident in lithium PFC research: decades of experiments have examined the effect of lithium PFCs on plasma performance, but the understanding of the lithium surface itself is much less complete. This latter information is critical to identifying the mechanisms by which lithium PFCs affect plasma performance. This research focused on such plasma-surface interactions in the Lithium Tokamak Experiment (LTX), a spherical torus designed to accommodate solid or liquid lithium as the primary PFC. Surface analysis was accomplished via the novel Materials Analysis and Particle Probe (MAPP) diagnostic system. In a series of experiments on LTX, the MAPP x-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS) capabilities were used for in vacuo interrogation of PFC samples. This represented the first application of XPS and TDS for in situ surface analysis of tokamak PFCs. Surface analysis indicated that the thin (dLi ˜ 100nm) evaporative lithium PFC coatings in LTX were converted to Li2O due to oxidizing agents in both the residual vacuum and the PFC substrate. Conversion was rapid and nearly independent of PFC temperature, forming a majority Li2O surface within minutes and an entirely Li2O surface within hours. However, Li2O PFCs were still capable of retaining hydrogen and sequestering impurities until the Li2 O was further oxidized to LiOH, a process that took weeks. For hydrogen retention, Li2O PFCs retained H+ from LTX plasma discharges, but no LiH formation was observed. Instead, results implied that H+ was only weakly-bound, such that it almost completely outgassed as H 2 within minutes. For impurity sequestration, LTX plasma performance---ascertained from plasma current and density measurements---progressively improved as plasma carbon and oxygen impurity levels fell. This was true for PFC conditioning by vacuum baking and argon glow discharge cleaning, as well as by lithium evaporation. Some evidence suggested that impurity sequestration was more important than hydrogen retention in enhancing LTX plasma performance. In contrast with expectations for lithium PFCs, heating the Li2 O PFCs in LTX caused increased plasma impurity levels that tended to reduce plasma performance.

Monitoring xenon purity in the LUX detector with a mass spectrometry system

NASA Astrophysics Data System (ADS)

Balajthy, Jon; LUX Experiment Collaboration

2015-04-01

The LUX dark matter search experiment is a 350 kg two-phase liquid/gas xenon time projection chamber located at the 4850 ft level of the Sanford Underground Research Facility in Lead, SD. To monitor for radioactive impurities such as krypton and impurities which limit charge yield such as oxygen, LUX uses a xenon sampling system consisting of a mass spectrometer and a liquid nitrogen cold trap. The cold trap separates the gaseous impurities from a small sample of xenon and allows them to pass to the mass spectrometer for analysis. We report here on results from the LUX xenon sampling program. We also report on methods to enhance the sensitivity of the cold trap technique in preparation for the next-generation LUX-ZEPLIN experiment which will have even more stringent purity requirements.

Enhanced Production of Acarbose and Concurrently Reduced Formation of Impurity C by Addition of Validamine in Fermentation of Actinoplanes utahensis ZJB-08196

PubMed Central

Xue, Ya-Ping; Qin, Jun-Wei; Wang, Ya-Jun; Wang, Yuan-Shan; Zheng, Yu-Guo

2013-01-01

Commercial production of acarbose is exclusively via done microbial fermentation with strains from the genera of Actinoplanes. The addition of C7N-aminocyclitols for enhanced production of acarbose and concurrently reduced formation of impurity C by cultivation of A. utahensis ZJB-08196 in 500-mL shake flasks was investigated, and validamine was found to be the most effective strategy. Under the optimal conditions of validamine addition, acarbose titer was increased from 3560 ± 128 mg/L to 4950 ± 156 mg/L, and impurity C concentration was concurrently decreased from 289 ± 24 mg/L to 107 ± 29 mg/L in batch fermentation after 168 h of cultivation. A further fed-batch experiment coupled with the addition of validamine (20 mg/L) in the fermentation medium prior to inoculation was designed to enhance the production of acarbose. When twice feedings of a mixture of 6 g/L glucose, 14 g/L maltose, and 9 g/L soybean flour were performed at 72 h and 96 h, acarbose titer reached 6606 ± 103 mg/L and impurity C concentration was only 212 ± 12 mg/L at 168 h of cultivation. Acarbose titer and proportion of acarbose/impurity C increased by 85.6% and 152.9% when compared with control experiments. This work demonstrates for the first time that validamine addition is a simple and effective strategy for increasing acarbose production and reducing impurity C formation. PMID:23484146

Thermodynamics of impurity-enhanced vacancy formation in metals

NASA Astrophysics Data System (ADS)

Bukonte, Laura; Ahlgren, Tommy; Heinola, Kalle

2017-01-01

Hydrogen induced vacancy formation in metals and metal alloys has been of great interest during the past couple of decades. The main reason for this phenomenon, often referred to as the superabundant vacancy formation, is the lowering of vacancy formation energy due to the trapping of hydrogen. By means of thermodynamics, we study the equilibrium vacancy formation in fcc metals (Pd, Ni, Co, and Fe) in correlation with the H amounts. The results of this study are compared and found to be in good agreement with experiments. For the accurate description of the total energy of the metal-hydrogen system, we take into account the binding energies of each trapped impurity, the vibrational entropy of defects, and the thermodynamics of divacancy formation. We demonstrate the effect of vacancy formation energy, the hydrogen binding, and the divacancy binding energy on the total equilibrium vacancy concentration. We show that the divacancy fraction gives the major contribution to the total vacancy fraction at high H fractions and cannot be neglected when studying superabundant vacancies. Our results lead to a novel conclusion that at high hydrogen fractions, superabundant vacancy formation takes place regardless of the binding energy between vacancies and hydrogen. We also propose the reason of superabundant vacancy formation mainly in the fcc phase. The equations obtained within this work can be used for any metal-impurity system, if the impurity occupies an interstitial site in the lattice.

Eutectic Experiment Development for Space Processing

NASA Technical Reports Server (NTRS)

Hopkins, R. H.

1972-01-01

A ground base test plan and a specimen evaluation scheme have been developed for the aluminum-copper eutectic solidification experiment to be run in the M518 multipurpose electric furnace during the Skylab mission. Besides thermal and solidification studies a detailed description is given of the quantitative metallographic technique which is appropriate for characterizing eutectic structures. This method should prove a key tool for evaluating specimen microstructure which is the most sensitive indicator of changes produced during solidification. It has been recommended that single grain pre-frozen eutectic specimens be used to simplify microstructural evaluation and to eliminate any porosity in the as-cast eutectic specimens. High purity (99.999%) materials from one supplier should be employed for all experiments. Laboratory studies indicate that porosity occurs in the MRC as-cast eutectic ingots but that this porosity can be eliminated by directional freezing. Chemical analysis shows that the MRC ingots are slightly Al rich and contain about .03% impurity. Because of the impurity content the lower cooldown rate (1.2 C/min) should be used for eutectic freezing if MRC material is used in the M518 furnace.

Ion Heating During Local Helicity Injection Plasma Startup in the Pegasus ST

NASA Astrophysics Data System (ADS)

Burke, M. G.; Barr, J. L.; Bongard, M. W.; Fonck, R. J.; Hinson, E. T.; Perry, J. M.; Reusch, J. A.

2015-11-01

Plasmas in the Pegasus ST are initiated either through standard, MHD stable, inductive current drive or non-solenoidal local helicity injection (LHI) current drive with strong reconnection activity, providing a rich environment to study ion dynamics. During LHI discharges, a large amount of impurity ion heating has been observed, with the passively measured impurity Ti as high as 800 eV compared to Ti ~ 60 eV and Te ~ 175 eV during standard inductive current drive discharges. In addition, non-thermal ion velocity distributions are observed and appear to be strongest near the helicity injectors. The ion heating is hypothesized to be a result of large-scale magnetic reconnection activity, as the amount of heating scales with increasing fluctuation amplitude of the dominant, edge localized, n =1 MHD mode. An approximate temporal scaling of the heating with the amplitude of higher frequency magnetic fluctuations has also been observed, with large amounts of power spectral density present at several impurity ion cyclotron frequencies. Recent experiments have focused on investigating the impurity ion heating scaling with the ion charge to mass ratio as well as the reconnecting field strength. The ion charge to mass ratio was modified by observing different impurity charge states in similar LHI plasmas while the reconnecting field strength was modified by changing the amount of injected edge current. Work supported by US DOE grant DE-FG02-96ER54375.

Chemometrically assisted development and validation of LC-MS/MS method for the analysis of potential genotoxic impurities in meropenem active pharmaceutical ingredient.

PubMed

Grigori, Katerina; Loukas, Yannis L; Malenović, Anđelija; Samara, Vicky; Kalaskani, Anastasia; Dimovasili, Efi; Kalovidouri, Magda; Dotsikas, Yannis

2017-10-25

A sensitive Liquid Chromatography tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantitative analysis of three potential genotoxic impurities (318BP, M9, S5) in meropenem Active Pharmaceutical Ingredient (API). Due to the requirement for LOD values in ppb range, a high concentration of meropenem API (30mg/mL) had to be injected. Therefore, efficient determination of meropenem from its impurities became a critical aim of this study, in order to divert meropenem to waste, via a switching valve. ‎ After the selection of the important factors affecting analytes' elution, a Box-Behnken design was utilized to set the plan of experiments conducted with UV detector. As responses, the separation factor s between the last eluting impurity and meropenem, as well as meropenem retention factor k were used. Grid point search methodology was implemented aiming to obtain the optimal conditions that simultaneously comply to the conflicted criteria. Optimal mobile phase consisted of ACN, methanol and 0.09% HCOOH at a ratio 71/3.5/15.5v/v. All impurities and internal standard omeprazole were eluted before 7.5min and at 8.0min the eluents were directed to waste. The protocol was transferred to LC-MS/MS and validated according to ICH guidelines. Copyright © 2017 Elsevier B.V. All rights reserved.

[Standard addition determination of impurities in Na2CrO4 by ICP-AES].

PubMed

Wang, Li-ping; Feng, Hai-tao; Dong, Ya-ping; Peng, Jiao-yu; Li, Wu; Shi, Hai-qin; Wang, Yong

2015-02-01

Coupled plasma atomic emission spectrometry (ICP-AES) was used to determine the trace impurities of Ca, Mg, Al, Fe and Si in industrial sodium chromate. Wavelengths of 167.079, 393.366, 259.940, 279.533 and 251.611 nm were selected as analytical lines for the determination of Al, Ca, Fe, Mg and Si, respectively. The analytical errors can be eliminated by adjusting the determined solution with high pure hydrochloric acid. Standard addition method was used to eliminate matrix effects. The linear correlation, detection limit, precision and recovery for the concerned trace impurities have been examined. The effect of standard addition method on the accuracy for the determination under the selected analytical lines has been studied in detail. The results show that the linear correlations of standard curves were very good (R2 = 0.9988 to 0.9996) under the determined conditions. Detection limits of these trace impurities were in the range of 0.0134 to 0.0280 mg x L(-1). Sample recoveries were within 97.30% to 107.50%, and relative standard deviations were lower than 5.86% for eleven repeated determinations. The detection limits and accuracies established by the experiment can meet the analytical requirements and the analytic procedure was used to determine trace impurities in sodium chromate by ion membrane electrolysis technique successfully. Due to sodium chromate can be changed into sodium dichromate and chromic acid by adding acids, the established method can be further used to monitor trace impurities in these compounds or other hexavalent chromium compounds.

Growth Defects in Biomacromolecular Crystals

NASA Technical Reports Server (NTRS)

2003-01-01

NASA's ground based program confirmed close similarity between protein and small molecules crystal growth, but also revealed essential differences. No understanding exists as to why and when crystals grown in space are, in approx. 20 percent of cases, of higher quality. More rationale is needed in flight experiments. Ferritin crystals grown in space are 2.5 times cleaner than their terrestrial counterparts. This may occur because of the existence of a zone depleted with respect to impurities around a crystal growing in stagnant solution. This zone should appear since the distribution coefficient for homologous impurities exceeds unity. This impurity depletion zone hypothesis requires verification and development. Thorough purification from homologous impurities brought about resolution improvement from 2.6 to 1.8 angstroms for ferritin and from 2.6 to 2.0 angstroms for canavalin.

A Finite Difference Method for Modeling Migration of Impurities in Multilayer Systems

NASA Astrophysics Data System (ADS)

Tosa, V.; Kovacs, Katalin; Mercea, P.; Piringer, O.

2008-09-01

A finite difference method to solve the one-dimensional diffusion of impurities in a multilayer system was developed for the special case in which a partition coefficient K impose a ratio of the concentrations at the interface between two adiacent layers. The fictitious point method was applied to derive the algebraic equations for the mesh points at the interface, while for the non-uniform mesh points within the layers a combined method was used. The method was tested and then applied to calculate migration of impurities from multilayer systems into liquids or solids samples, in migration experiments performed for quality testing purposes. An application was developed in the field of impurities migrations from multilayer plastic packagings into food, a problem of increasing importance in food industry.

Impurities block the alpha to omega martensitic transformation in titanium.

PubMed

Hennig, Richard G; Trinkle, Dallas R; Bouchet, Johann; Srinivasan, Srivilliputhur G; Albers, Robert C; Wilkins, John W

2005-02-01

Impurities control phase stability and phase transformations in natural and man-made materials, from shape-memory alloys to steel to planetary cores. Experiments and empirical databases are still central to tuning the impurity effects. What is missing is a broad theoretical underpinning. Consider, for example, the titanium martensitic transformations: diffusionless structural transformations proceeding near the speed of sound. Pure titanium transforms from ductile alpha to brittle omega at 9 GPa, creating serious technological problems for beta-stabilized titanium alloys. Impurities in the titanium alloys A-70 and Ti-6Al-4V (wt%) suppress the transformation up to at least 35 GPa, increasing their technological utility as lightweight materials in aerospace applications. These and other empirical discoveries in technological materials call for broad theoretical understanding. Impurities pose two theoretical challenges: the effect on the relative phase stability, and the energy barrier of the transformation. Ab initio methods calculate both changes due to impurities. We show that interstitial oxygen, nitrogen and carbon retard the transformation whereas substitutional aluminium and vanadium influence the transformation by changing the d-electron concentration. The resulting microscopic picture explains the suppression of the transformation in commercial A-70 and Ti-6Al-4V alloys. In general, the effect of impurities on relative energies and energy barriers is central to understanding structural phase transformations.

Role of impurities in magnetically confined high temperature plasmas

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

Barnett, C.F.

1976-01-01

A summary is given of the atomic physics concerned with plasma cooling by impurities and the limiting effect that impurities may have on heating of plasmas by neutral injection. A general description is given of the tokamak concept and the present and next generation experiments are described. The time and spatial behavior of O and Mo multicharged ions in present hydrogen plasmas is presented. This is followed by a discussion of the power loss from a plasma containing one percent Fe. Finally, the limitation of plasma heating by energetic H or D injection is summarized. (MOW)

Modeling Electronegative Impurity Concentrations in Liquid Argon Detectors

NASA Astrophysics Data System (ADS)

Tang, Wei; Li, Yichen; Thorn, Craig; Qian, Xin

2017-01-01

Achieving long electron lifetime is crucial to reach the high performance of large Liquid Argon Time Projection Chamber (LArTPC) envisioned for next generation neutrino experiments. We have built up a quantitative model to describe the impurity distribution and transportation in a cryostat. Henrys constants of Oxygen and water, which describe the partition of impurities between gas argon and liquid argon, have been deduced through this model with the measurements in BNL 20-L LAr test stand. These results indicate the importance of the gas purification system and prospects on large LArTPC detectors will be discussed.

Benchmarking atomic physics models for magnetically confined fusion plasma physics experiments

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

May, M.J.; Finkenthal, M.; Soukhanovskii, V.

In present magnetically confined fusion devices, high and intermediate {ital Z} impurities are either puffed into the plasma for divertor radiative cooling experiments or are sputtered from the high {ital Z} plasma facing armor. The beneficial cooling of the edge as well as the detrimental radiative losses from the core of these impurities can be properly understood only if the atomic physics used in the modeling of the cooling curves is very accurate. To this end, a comprehensive experimental and theoretical analysis of some relevant impurities is undertaken. Gases (Ne, Ar, Kr, and Xe) are puffed and nongases are introducedmore » through laser ablation into the FTU tokamak plasma. The charge state distributions and total density of these impurities are determined from spatial scans of several photometrically calibrated vacuum ultraviolet and x-ray spectrographs (3{endash}1600 {Angstrom}), the multiple ionization state transport code transport code (MIST) and a collisional radiative model. The radiative power losses are measured with bolometery, and the emissivity profiles were measured by a visible bremsstrahlung array. The ionization balance, excitation physics, and the radiative cooling curves are computed from the Hebrew University Lawrence Livermore atomic code (HULLAC) and are benchmarked by these experiments. (Supported by U.S. DOE Grant No. DE-FG02-86ER53214 at JHU and Contract No. W-7405-ENG-48 at LLNL.) {copyright} {ital 1999 American Institute of Physics.}« less

Effect of impurities and post-experimental purification in SAD phasing with serial femtosecond crystallography data.

PubMed

Zhang, Tao; Gu, Yuanxin; Fan, Haifu

2016-06-01

In serial crystallography (SX) with either an X-ray free-electron laser (XFEL) or synchrotron radiation as the light source, huge numbers of micrometre-sized crystals are used in diffraction data collection. For a SAD experiment using a derivative with introduced heavy atoms, it is difficult to completely exclude crystals of the native protein from the sample. In this paper, simulations were performed to study how the inclusion of native crystals in the derivative sample could affect the result of SAD phasing and how the post-experimental purification proposed by Zhang et al. [(2015), Acta Cryst. D71, 2513-2518] could be used to remove the impurities. A gadolinium derivative of lysozyme and the corresponding native protein were used in the test. Serial femtosecond crystallography (SFX) diffraction snapshots were generated by CrystFEL. SHELXC/D, Phaser, DM, ARP/wARP and REFMAC were used for automatic structure solution. It is shown that a small amount of impurities (snapshots from native crystals) in the set of derivative snapshots can strongly affect the SAD phasing results. On the other hand, post-experimental purification can efficiently remove the impurities, leading to results similar to those from a pure sample.

Test of prototype ITER vacuum ultraviolet spectrometer and its application to impurity study in KSTAR plasmas.

PubMed

Seon, C R; Hong, J H; Jang, J; Lee, S H; Choe, W; Lee, H H; Cheon, M S; Pak, S; Lee, H G; Biel, W; Barnsley, R

2014-11-01

To optimize the design of ITER vacuum ultraviolet (VUV) spectrometer, a prototype VUV spectrometer was developed. The sensitivity calibration curve of the spectrometer was calculated from the mirror reflectivity, the grating efficiency, and the detector efficiency. The calibration curve was consistent with the calibration points derived in the experiment using the calibrated hollow cathode lamp. For the application of the prototype ITER VUV spectrometer, the prototype spectrometer was installed at KSTAR, and various impurity emission lines could be measured. By analyzing about 100 shots, strong positive correlation between the O VI and the C IV emission intensities could be found.

Parity Anomaly and Spin Transmutation in Quantum Spin Hall Josephson Junctions.

PubMed

Peng, Yang; Vinkler-Aviv, Yuval; Brouwer, Piet W; Glazman, Leonid I; von Oppen, Felix

2016-12-23

We study the Josephson effect in a quantum spin Hall system coupled to a localized magnetic impurity. As a consequence of the fermion parity anomaly, the spin of the combined system of impurity and spin-Hall edge alternates between half-integer and integer values when the superconducting phase difference across the junction advances by 2π. This leads to characteristic differences in the splittings of the spin multiplets by exchange coupling and single-ion anisotropy at phase differences, for which time-reversal symmetry is preserved. We discuss the resulting 8π-periodic (or Z_{4}) fractional Josephson effect in the context of recent experiments.

Glycolic acid physical properties and impurities assessment

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

Lambert, D. P.; Pickenheim, B. R.; Hay, M. S.

This document has been revised to add analytical data for fresh, 1 year old, and 4 year old glycolic acid as recommended in Revision 2 of this document. This was needed to understand the concentration of formaldehyde and methoxyacetic acid, impurities present in the glycolic acid used in Savannah River National Laboratory (SRNL) experiments. Based on this information, the concentration of these impurities did not change during storage. These impurities were in the glycolic acid used in the testing included in this report and in subsequent testing using DuPont (now called Chemours) supplied Technical Grade 70 wt% glycolic acid. However,more » these impurities were not reported in the first two versions of this report. The Defense Waste Processing Facility (DWPF) is planning to implement a nitric-glycolic acid flowsheets to increase attainment to meet closure commitment dates during Sludge Batch 9. In fiscal year 2009, SRNL was requested to determine the physical properties of formic and glycolic acid blends.« less

Using a Simulated Industrial Setting for the Development of an Improved Solvent System for the Recrystallization of Benzoic Acid: A Student-Centered Project

ERIC Educational Resources Information Center

Hightower, Timothy R.; Heeren, Jay D.

2006-01-01

Recrystallization of benzoic acid is an excellent way to remove insoluble impurities. In a traditional organic laboratory experiment, insoluble impurities are removed through the recrystallization of benzoic acid utilizing water as the recrystallization solvent. It was our goal to develop a peer-led, problem-solving organic laboratory exercise…

Impact of perturbative, non-axisymmetric impurity fueling on Alcator C-Mod H-modes

NASA Astrophysics Data System (ADS)

Reinke, M. L.; Lore, J. D.; Terry, J.; Brunner, D.; LaBombard, B.; Lipschultz, B.; Hubbard, A.; Hughes, J. W.; Mumgaard, R.; Pitts, R. A.

2017-12-01

Experiments on Alcator C-Mod have been performed to investigate the impact of toroidally localized impurity injection on H-mode exhaust scenarios. Results help to inform sub-divertor gas injector designs, in particular that of the ITER machine, for which this work was primarily undertaken. In repeated EDA H-modes, the amount of N2 injected into the private flux region was scanned up to levels which strongly impacted normalized energy confinement, H98, and led to an H/L back-transition. Repeated scans increased the toroidal peaking of the gas injection, reducing from five equally spaced locations to a single toroidal and poloidal injector. Results show the impact on the pedestal and core plasma is similar between all cases as long as the total gas injection rate is held constant. An influence on toroidally localized impurity spectroscopy is shown, demonstrating a complication in using such data in interpreting experiments and supporting boundary modeling in cases where there are localized extrinsic or intrinsic impurity sources. These results, along with prior work in this area on Alcator C-Mod, form a comprehensive set of L-mode and H-mode data to be used for validation of 3D boundary physics codes.

Near-infrared spectroscopy for burning plasma diagnostic applications.

PubMed

Soukhanovskii, V A

2008-10-01

Ultraviolet and visible (UV-VIS, 200-750 nm) atomic spectroscopy of neutral and ionized fuel species (H, D, T, and Li) and impurities (e.g., He, Be, C, and W) is a key element of plasma control and diagnosis on International Thermonuclear Experimental Reactor and future magnetically confined burning plasma experiments (BPXs). Spectroscopic diagnostic implementation and performance issues that arise in the BPX harsh nuclear environment in the UV-VIS range, e.g., degradation of first mirror reflectivity under charge-exchange atom bombardment (erosion) and impurity deposition, permanent and dynamic loss of window, and optical fiber transmission under intense neutron and gamma-ray fluxes, are either absent or not as severe in the near-infrared (NIR, 750-2000 nm) range. An initial survey of NIR diagnostic applications has been undertaken on the National Spherical Torus Experiment. It is demonstrated that NIR spectroscopy can be used for machine protection and plasma control applications, as well as contribute to plasma performance evaluation and physics studies. Emission intensity estimates demonstrate that NIR measurements are possible in the BPX plasma operating parameter range. Complications in the NIR range due to the parasitic background emissions are expected to occur at very high plasma densities, low impurity densities, and at high plasma-facing component temperatures.

Particle and momentum confinement in tokamak plasmas with unbalanced neutral beam injection and strong rotation

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

Malik, M.A.

1988-01-01

There is a self-consistent theory of the effects of neutral beam injection on impurity transport in tokamak plasmas. The theory predicts that co-injection drives impurities outward and that counter-injection enhances the normally inward flow of impurities. The theory was applied to carry out a detailed analysis of the large experimental database from the PLT and the ISX-B tokamaks. The theory was found to generally model the experimental data quite well. It is, therefore, concluded that neutral beam co-injection can drive impurities outward to achieve clean central plasmas and a cool radiating edge. Theoretical predictions for future thermonuclear reactors such asmore » INTOR, TIBER II, and ITER indicated that neutral beam driven flow reversal might be an effective impurity control method if the rate of beam momentum deposited per plasma ion is adequate. The external momentum drag, which is a pivotal concept in impurity flow reversal theory, is correctly predicted by the gyroviscous theory of momentum confinement. The theory was applied to analyze experimental data from the PLT and the PDX tokamaks with exact experimental conditions. The theory was found to be in excellent agreement with experiment over a wide range of parameters. It is, therefore, possible to formulate the impurity transport theory from first principles, without resort to empiricism.« less

Impurity effect of iron(III) on the growth of potassium sulfate crystal in aqueous solution

NASA Astrophysics Data System (ADS)

Kubota, Noriaki; Katagiri, Ken-ichi; Yokota, Masaaki; Sato, Akira; Yashiro, Hitoshi; Itai, Kazuyoshi

1999-01-01

Growth rates of the {1 1 0} faces of a potassium sulfate crystal were measured in a flow cell in the presence of traces of impurity Fe(III) (up to 2 ppm) over the range of pH=2.5-6.0. The growth rate was significantly suppressed by the impurity. The effect became stronger as the impurity concentration was increased and at pH<5. It became weaker with increasing supersaturation. It also became weaker as the pH was increased and at pH>5 it finally disappeared completely. The concentration and supersaturation effects on the impurity action were reasonably explained with a model proposed by Kubota and Mullin [J. Crystal Growth, 152 (1995) 203]. The surface coverage of the active sites by Fe(III) is estimated to increase linearly on increasing its concentration in solution in the range examined by growth experiments. The impurity effectiveness factor is confirmed to increase inversely proportional to the supersaturation as predicted by the model. Apart from the discussion based on the model, the pH effect on the impurity action is qualitatively explained by assuming that the first hydrolysis product of aqua Fe(III) complex compound, [Fe(H 2O) 5(OH)] 2+, is both growth suppression and adsorption active, but the second hydrolysis product, [Fe(H 2O) 4(OH) 2] +, is only adsorption active.

Acetylated Lysozyme as Impurity in Lysozyme Crystals: Constant Distribution Coefficient

NASA Technical Reports Server (NTRS)

Thomas, B. R.; Chernov, A. A.

2000-01-01

Hen egg white lysozyme (HEWL) was acetylated to modify molecular charge keeping the molecular size and weight nearly constant. Two derivatives, A and B, more and less acetylated, respectively, were obtained, separated, purified and added to the solution from which crystals of tetragonal HEWL crystals were grown. Amounts of the A or B impurities added were 0.76, 0.38 and 0.1 milligram per millimeter while HEWL concentration were 20, 30 and 40 milligram per milliliter. The crystals grown in 18 experiments for each impurity were dissolved and quantities of A or B additives in these crystals were analyzed by cation exchange high performance liquid chromatography. All the data for each set of 18 samples with the different impurity and regular HEWL concentrations is well described by one distribution coefficient K = 2.15 plus or minus 0.13 for A and K = 3.42 plus or minus 0.25 for B. The observed independence of the distribution coefficient on both the impurity concentration and supersaturation is explained by the dilution model described in this paper. It shows that impurity adsorption and incorporation rate is proportional to the impurity concentration and that the growth rate is proportional to the crystallizing protein in solution. With the kinetic coefficient for crystallization, beta = 5.10(exp -7) centimeters per second, the frequency at which an impurity molecule near the growing interface irreversibly joins a molecular site on the crystal was found to be 3 1 per second, much higher than the average frequency for crystal molecules. For best quality protein crystals it is better to have low microheterogeneous protein impurity concentration and high supers aturation.

Effect of Feedstock and Catalyst Impurities on the Methanol‐to‐Olefin Reaction over H‐SAPO‐34

PubMed Central

Vogt, Charlotte; Ruiz‐Martínez, Javier

2016-01-01

Abstract Operando UV/Vis spectroscopy with on‐line mass spectrometry was used to study the effect of different types of impurities on the hydrocarbon pool species and the activity of H‐SAPO‐34 as a methanol‐to‐olefins (MTO) catalyst. Successive reaction cycles with different purity feedstocks were studied, with an intermittent regeneration step. The combined study of two distinct impurity types (i.e., feed and internal impurities) leads to new insights into MTO catalyst activation and deactivation mechanisms. In the presence of low amounts of feed impurities, the induction and active periods of the process are prolonged. Feed impurities are thus beneficial in the formation of the initial hydrocarbon pool, but also aid in the unwanted formation of deactivating coke species by a separate, competing mechanism favoring coke species over olefins. Further, feedstock impurities strongly influence the location of coke deposits, and thus influence the deactivation mechanism, whereas a study of the organic impurities retained after calcination reveals that these species are less relevant for catalyst activity and function as “seeds” for coke formation only. PMID:28163792

Study of the structures of photodegradation impurities and pathways of photodegradation of cilnidipine by liquid chromatography/Q-Orbitrap mass spectrometry.

PubMed

Zeng, Hongxia; Wang, Fan; Zhu, Bingqi; Zhong, Weihui; Shan, Weiguang; Wang, Jian

2016-08-15

The structures of photodegradation impurities in cilnidipine were studied by liquid chromatography/Q-Orbitrap mass spectrometry (LC/Q-Orbitrap MS) for the further improvement of the official monographs in Pharmacopoeias. The complete fragmentation patterns of impurities were investigated to obtain their structural information. Two pathways of photodegradation of cilnidipine were also explored to clarify the source of impurities in cilnidipine. Chromatographic separation was performed on a Boston Group C18 column (250 mm × 4.6 mm, 5 μm). The mobile phase consisted of acetonitrile/H2 O at a ratio of 75:25 (v/v). In order to determine the m/z values of the molecular ions and formulas of all detected impurities, full scan LC/MS in both positive and negative ion modes was firstly performed using a Thermo LC system coupled with a Q-Orbitrap high-resolution mass spectrometer. LC/MS/MS analysis was also carried out on target compounds to obtain as much structural information as possible. Five novel photodegradation impurities of cilnidipine were separated and identified based on the high-resolution MS/MS data. Impurity III was synthesized and its structure was confirmed by (1) H-NMR and (13) C-NMR data. Two photodegradation pathways to produce different photodegradation impurities were also revealed in this study. Among those impurities, impurities II and III were the main impurities which existed in the cilnidipine available on the market. Impurity II (the Z-isomer) was mainly produced when cilnidipine powder was directly exposed to daylight while impurity III (containing a piperidine ring) was mainly produced when cilnidipine was exposed to daylight in an ethanolic solution. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Apoferritin crystals

NASA Technical Reports Server (NTRS)

2001-01-01

Dr. Alexander Chernov, of the Universities Space Research Association (USRA) and based at Marshall Space Flight Center, is investigating why protein crystals grown in space are, in about 20 percent of cases, better-ordered than those grown on the ground. They are testing the idea that the amount of impurities trapped by space-grown crystals may be different than the amount trapped by crystals grown on Earth because convection is negligible in microgravity. The concentrations or impurities in many space-grown crystals turned out to be several times lower than that in the terrestrial ones, sometimes below the detection limit. The ground-based experiment also showed that the amount of impurities per unit volume of the crystals was usually higher than the amount per unit volume of the solution. This means that a growing crystal actually purifies the solution in its immediate vicinity. Here, an impurity depletion zone is created around apoferritin crystals grown in gel, imitating microgravity conditions.

Microgravity

NASA Image and Video Library

2001-01-24

Dr. Alexander Chernov, of the Universities Space Research Association (USRA) and based at Marshall Space Flight Center, is investigating why protein crystals grown in space are, in about 20 percent of cases, better-ordered than those grown on the ground. They are testing the idea that the amount of impurities trapped by space-grown crystals may be different than the amount trapped by crystals grown on Earth because convection is negligible in microgravity. The concentrations or impurities in many space-grown crystals turned out to be several times lower than that in the terrestrial ones, sometimes below the detection limit. The ground-based experiment also showed that the amount of impurities per unit volume of the crystals was usually higher than the amount per unit volume of the solution. This means that a growing crystal actually purifies the solution in its immediate vicinity. Here, an impurity depletion zone is created around apoferritin crystals grown in gel, imitating microgravity conditions.

Passive particle dosimetry. [silver halide crystal growth

NASA Technical Reports Server (NTRS)

Childs, C. B.

1977-01-01

Present methods of dosimetry are reviewed with emphasis on the processes using silver chloride crystals for ionizing particle dosimetry. Differences between the ability of various crystals to record ionizing particle paths are directly related to impurities in the range of a few ppm (parts per million). To understand the roles of these impurities in the process, a method for consistent production of high purity silver chloride, and silver bromide was developed which yields silver halides with detectable impurity content less than 1 ppm. This high purity silver chloride was used in growing crystals with controlled doping. Crystals were grown by both the Czochalski method and the Bridgman method, and the Bridgman grown crystals were used for the experiments discussed. The distribution coefficients of ten divalent cations were determined for the Bridgman crystals. The best dosimeters were made with silver chloride crystals containing 5 to 10 ppm of lead; other impurities tested did not produce proper dosimeters.

Proof-of-concept experiment for on-line laser induced breakdown spectroscopy analysis of impurity layer deposited on optical window and other plasma facing components of Aditya tokamak

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

Maurya, Gulab Singh; Kumar, Rohit; Rai, Awadhesh Kumar, E-mail: awadheshkrai@rediffmail.com

2015-12-15

In the present manuscript, we demonstrate the design of an experimental setup for on-line laser induced breakdown spectroscopy (LIBS) analysis of impurity layers deposited on specimens of interest for fusion technology, namely, plasma-facing components (PFCs) of a tokamak. For investigation of impurities deposited on PFCs, LIBS spectra of a tokamak wall material like a stainless steel sample (SS304) have been recorded through contaminated and cleaned optical windows. To address the problem of identification of dust and gases present inside the tokamak, we have shown the capability of the apparatus to record LIBS spectra of gases. A new approach known asmore » “back collection method” to record LIBS spectra of impurities deposited on the inner surface of optical window is presented.« less

Gamma-ray spectrometry of ultra low levels of radioactivity within the material screening program for the GERDA experiment.

PubMed

Budjás, D; Gangapshev, A M; Gasparro, J; Hampel, W; Heisel, M; Heusser, G; Hult, M; Klimenko, A A; Kuzminov, V V; Laubenstein, M; Maneschg, W; Simgen, H; Smolnikov, A A; Tomei, C; Vasiliev, S I

2009-05-01

In present and future experiments in the field of rare events physics a background index of 10(-3) counts/(keV kg a) or better in the region of interest is envisaged. A thorough material screening is mandatory in order to achieve this goal. The results of a systematic study of radioactive trace impurities in selected materials using ultra low-level gamma-ray spectrometry in the framework of the GERDA experiment are reported.

Cryogenic molecular separation system for radioactive (11)C ion acceleration.

PubMed

Katagiri, K; Noda, A; Suzuki, K; Nagatsu, K; Boytsov, A Yu; Donets, D E; Donets, E D; Donets, E E; Ramzdorf, A Yu; Nakao, M; Hojo, S; Wakui, T; Noda, K

2015-12-01

A (11)C molecular production/separation system (CMPS) has been developed as part of an isotope separation on line system for simultaneous positron emission tomography imaging and heavy-ion cancer therapy using radioactive (11)C ion beams. In the ISOL system, (11)CH4 molecules will be produced by proton irradiation and separated from residual air impurities and impurities produced during the irradiation. The CMPS includes two cryogenic traps to separate specific molecules selectively from impurities by using vapor pressure differences among the molecular species. To investigate the fundamental performance of the CMPS, we performed separation experiments with non-radioactive (12)CH4 gases, which can simulate the chemical characteristics of (11)CH4 gases. We investigated the separation of CH4 molecules from impurities, which will be present as residual gases and are expected to be difficult to separate because the vapor pressure of air molecules is close to that of CH4. We determined the collection/separation efficiencies of the CMPS for various amounts of air impurities and found desirable operating conditions for the CMPS to be used as a molecular separation device in our ISOL system.

Unsteady-state transfer of impurities during crystal growth of sucrose in sugarcane solutions

NASA Astrophysics Data System (ADS)

Martins, P. M.; Ferreira, A.; Polanco, S.; Rocha, F.; Damas, A. M.; Rein, P.

2009-07-01

In this work, we present growth rate data of sucrose crystals in the presence of impurities that can be used by both sugar technologists and crystal growth scientists. Growth rate curves measured in a pilot-scale evaporative crystallizer suggest a period of slow growth that follows the seeding of crystals into supersaturated technical solutions. The observed trend was enhanced by adding typical sugarcane impurities such as starch, fructose or dextran to the industrial syrups. Maximum growth rates of sucrose resulted at intermediate rather than high supersaturation levels in the presence of the additives. The effects of the additives on the sucrose solubility and sucrose mass transfer in solution were taken into account to explain the observed crystal growth kinetics. A novel mechanism was identified of unsteady-state adsorption of impurities at the crystal surface and their gradual replacement by the crystallizing solute towards the equilibrium occupation of the active sites for growth. Specifically designed crystallization experiments at controlled supersaturation confirmed this mechanism by showing increasing crystal growth rates with time until reaching a steady-state value for a given supersaturation level and impurity content.

First-principles calculations of optical transitions at native defects and impurities in ZnO

NASA Astrophysics Data System (ADS)

Lyons, John L.; Varley, Joel B.; Janotti, Anderson; Van de Walle, Chris G.

2018-02-01

Optical spectroscopy is a powerful approach for detecting defects and impurities in ZnO, an important electronic material. However, knowledge of how common optical signals are linked with defects and impurities is still limited. The Cu-related green luminescence is among the best understood luminescence signals, but theoretical descriptions of Cu-related optical processes have not agreed with experiment. Regarding native defects, assigning observed lines to specific defects has proven very difficult. Using first-principles calculations, we calculate the properties of native defects and impurities in ZnO and their associated optical signals. Oxygen vacancies are predicted to give luminescence peaks lower than 1 eV; while related zinc dangling bonds can lead to luminescence near 2.4 eV. Zinc vacancies lead to luminescence peaks below 2 eV, as do the related oxygen dangling bonds. However, when complexed with hydrogen impurities, zinc vacancies can cause higher-energy transitions, up to 2.3 eV. We also find that the Cu-related green luminescence is related to a (+/0) deep donor transition level.

Quasiclassical Theory on Third-Harmonic Generation in Conventional Superconductors with Paramagnetic Impurities

NASA Astrophysics Data System (ADS)

Jujo, Takanobu

2018-02-01

We investigate the third-harmonic generation (THG) of s-wave superconductors under microwave pulse irradiation. We consider the effect of paramagnetic impurities on the THG intensity of dirty superconductors. The nonlinear response function is calculated using the method of the quasiclassical Green function. It is shown that the amplitude mode is included as the vertex correction and makes a predominant contribution to the THG intensity. When the effect of paramagnetic impurities is weak, the THG intensity shows a peak at the temperature at which the superconducting gap is about the same as the frequency of the incident pulse, similarly to in experiments. As the effect of paramagnetic impurities is strengthened, the peak of the THG intensity disappears. This indicates that time-reversal symmetry breaking due to paramagnetic impurities eliminates the well-defined amplitude mode. The result of our calculation shows that the existence of the amplitude mode can be confirmed through the THG intensity. The result of a semiquantitative calculation is in good agreement with the experimental result, and it also shows that the diamagnetic term is negligible.

Probe-type of superconductivity by impurity in materials with short coherence length: the s-wave and η-wave phases study

NASA Astrophysics Data System (ADS)

Ptok, Andrzej; Jerzy Kapcia, Konrad

2015-04-01

The effects of a single non-magnetic impurity on superconducting states in the Penson-Kolb-Hubbard model have been analyzed. The investigations have been performed within the Hartree-Fock mean field approximation in two steps: (i) the homogeneous system is analysed using the Bogoliubov transformation, whereas (ii) the inhomogeneous system is investigated by self-consistent Bogoliubov-de Gennes equations (with the exact diagonalization and the kernel polynomial method). We analysed both signs of the pair hopping, which correspond to s-wave and η-wave superconductivity. Our results show that an enhancement of the local superconducting gap at the impurity-site occurs for both cases. We obtained that Cooper pairs are scattered (at the impurity site) into the states which are from the neighborhoods of the states, which are commensurate ones with the crystal lattice. Additionally, in the η-phase there are peaks in the local-energy gap (in momentum space), which are connected with long-range oscillations in the spatial distribution of the energy gap, superconducting order parameter (SOP), as well as effective pairing potential. Our results can be contrasted with the experiment and predicts how to experimentally differentiate these two different symmetries of SOP by the scanning tunneling microscopy technique.

Electrodeless Plasma Source: Phase II Update

NASA Astrophysics Data System (ADS)

Prager, James; Ziemba, Timothy; Miller, Kenneth

2012-10-01

Eagle Harbor Technologies, in collaboration with the University of Washington, has developed a low-impurity, electrode-less plasma source (EPS) for start-up and source plasma injection for fusion science applications. In order to not interfere with the experiment, a pre-ionizer/plasma source must meet a few critical criteria including low impurity production, low electromagnetic interference (EMI), and minimal disruption to the magnetic geometry of the experiment. This system was designed to be UHV compatible and bakable. Here we present the results of the EPS Phase II upgrade. The output plasma density was increased by two orders of magnitude to >10^17 m-3 in hydrogen with no magnetic field injected. EPS system integration with the HIT-SI experiment has begun.

Suppression of Superfluid Density and the Pseudogap State in the Cuprates by Impurities

DOE PAGES

Erdenemunkh, Unurbat; Koopman, Brian; Fu, Ling; ...

2016-12-16

Here, we use scanning tunneling microscopy (STM) to study magnetic Fe impurities intentionally doped into the high-temperature superconductor Bi 2Sr 2CaCu 2O 8+δ. Our spectroscopic measurements reveal that Fe impurities introduce low-lying resonances in the density of states at Ω 1 ≈ 4 meV and Ω 2 ≈ 15 meV , allowing us to determine that, despite having a large magnetic moment, potential scattering of quasiparticles by Fe impurities dominates magnetic scattering. In addition, using high-resolution spatial characterizations of the local density of states near and away from Fe impurities, we detail the spatial extent of impurity-affected regions as wellmore » as provide a local view of impurity-induced effects on the superconducting and pseudogap states. Lastly, our studies of Fe impurities, when combined with a reinterpretation of earlier STM work in the context of a two-gap scenario, allow us to present a unified view of the atomic-scale effects of elemental impurities on the pseudogap and superconducting states in hole-doped cuprates; this may help resolve a previously assumed dichotomy between the effects of magnetic and nonmagnetic impurities in these materials.« less

Silicon materials task of the low cost solar array project. Phase 3: Effect of impurities and processing on silicon solar cells

NASA Technical Reports Server (NTRS)

Hopkins, R. H.; Davis, J. R.; Blais, P. D.; Rohatgi, A.; Campbell, R. B.; Rai-Choudhury, P.; Mollenkopf, H. C.; Mccormick, J. R.

1979-01-01

The 13th quarterly report of a study entitled an Investigation of the Effects of Impurities and Processing on Silicon Solar Cells is given. The objective of the program is to define the effects of impurities, various thermochemical processes and any impurity-process interactions on the performance of terrestrial silicon solar cells. The Phase 3 program effort falls in five areas: (1) cell processing studies; (2) completion of the data base and impurity-performance modeling for n-base cells; (3) extension of p-base studies to include contaminants likely to be introduced during silicon production, refining or crystal growth; (4) anisotropy effects; and (5) a preliminary study of the permanence of impurity effects in silicon solar cells. The quarterly activities for this report focus on tasks (1), (3) and (4).

Effects of Impurities and Processing on Silicon Solar Cells, Phase 3

NASA Technical Reports Server (NTRS)

Hopkins, R. H.; Davis, J. R.; Blais, P. D.; Rohatgi, A.; Campbell, R. B.; Rai-Choudhury, P.; Stapleton, R. E.; Mollenkopf, H. C.; Mccormick, J. R.

1979-01-01

Results of the 14th quarterly report are presented for a program designed to assess the effects of impurities, thermochemical processes and any impurity process interactions on the performance of terrestrial silicon solar cells. The Phase 3 effort encompasses: (1) potential interactions between impurities and thermochemical processing of silicon; (2) impurity-cell performance relationships in n-base silicon; (3) effect of contaminants introduced during silicon production, refining or crystal growth on cell performance; (4) effects of nonuniform impurity distributions in large area silicon wafers; and (5) a preliminary study of the permanence of impurity effects in silicon solar cells.

Renewal of an old European Pharmacopoeia method for Terazosin using modeling with mass spectrometric peak tracking.

PubMed

Kormány, Róbert; Molnár, Imre; Fekete, Jenő

2017-02-20

An older method for terazosin was reworked in order to reduce the analysis time from 90min (2×45min) to below 5min. The method in European Pharmacopoeia (Ph.Eur.) investigates the specified impurities separately. The reason of the different methods is that the retention of two impurities is not adequate in reversed phase, not even with 100% water. Therefore ion-pair-chromatography has to be applied and since that two impurities absorb at low UV-wavelength they had to be analyzed by different method than the other specified impurities. In our new method we could improve the retention with pH elevation using a new type of stationary phases available for high pH applications. Also a detection wavelength could be selected that is appropriate for the detection and quantification of all impurities. The method development is the bottleneck of liquid chromatography even today, when more and more fast chromatographic systems are used. Expert knowledge with intelligent programs is available to reduce the time of method development and offer extra information about the robustness of the separation. Design of Experiments (DoE) for simultaneous optimization of gradient time (t G ), temperature (T) and ternary eluent composition (t C ) requires 12 experiments. A good alternative way to identify a certain peak in different chromatograms is the molecular mass of the compound, due to its high specificity. Liquid Chromatography-Mass Spectrometry (LC-MS) is now a routine technique and increasingly available in laboratories. In our experiment for the resolution- and retention modeling the DryLab4 method development software (Version 4.2) was used. In recent versions of the software the use of (m/z)-MS-data is possible along the UV-peak-area-tracking technology. The modelled and measured chromatograms showed excellent correlations. The average retention time deviations were ca. 0.5s and there was no difference between the predicted and measured R s,crit -values. Copyright © 2016. Published by Elsevier B.V.

A quasi-linear analysis of the impurity effect on turbulent momentum transport and residual stress

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

Ko, S. H., E-mail: shko@nfri.re.kr; Jhang, Hogun; Singh, R.

2015-08-15

We study the impact of impurities on turbulence driven intrinsic rotation (via residual stress) in the context of the quasi-linear theory. A two-fluid formulation for main and impurity ions is employed to study ion temperature gradient modes in sheared slab geometry modified by the presence of impurities. An effective form of the parallel Reynolds stress is derived in the center of mass frame of a coupled main ion-impurity system. Analyses show that the contents and the radial profile of impurities have a strong influence on the residual stress. In particular, an impurity profile aligned with that of main ions ismore » shown to cause a considerable reduction of the residual stress, which may lead to the reduction of turbulence driven intrinsic rotation.« less

Extension of the operational regime of the LHD towards a deuterium experiment

NASA Astrophysics Data System (ADS)

Takeiri, Y.; Morisaki, T.; Osakabe, M.; Yokoyama, M.; Sakakibara, S.; Takahashi, H.; Nakamura, Y.; Oishi, T.; Motojima, G.; Murakami, S.; Ito, K.; Ejiri, A.; Imagawa, S.; Inagaki, S.; Isobe, M.; Kubo, S.; Masamune, S.; Mito, T.; Murakami, I.; Nagaoka, K.; Nagasaki, K.; Nishimura, K.; Sakamoto, M.; Sakamoto, R.; Shimozuma, T.; Shinohara, K.; Sugama, H.; Watanabe, K. Y.; Ahn, J. W.; Akata, N.; Akiyama, T.; Ashikawa, N.; Baldzuhn, J.; Bando, T.; Bernard, E.; Castejón, F.; Chikaraishi, H.; Emoto, M.; Evans, T.; Ezumi, N.; Fujii, K.; Funaba, H.; Goto, M.; Goto, T.; Gradic, D.; Gunsu, Y.; Hamaguchi, S.; Hasegawa, H.; Hayashi, Y.; Hidalgo, C.; Higashiguchi, T.; Hirooka, Y.; Hishinuma, Y.; Horiuchi, R.; Ichiguchi, K.; Ida, K.; Ido, T.; Igami, H.; Ikeda, K.; Ishiguro, S.; Ishizaki, R.; Ishizawa, A.; Ito, A.; Ito, Y.; Iwamoto, A.; Kamio, S.; Kamiya, K.; Kaneko, O.; Kanno, R.; Kasahara, H.; Kato, D.; Kato, T.; Kawahata, K.; Kawamura, G.; Kisaki, M.; Kitajima, S.; Ko, W. H.; Kobayashi, M.; Kobayashi, S.; Kobayashi, T.; Koga, K.; Kohyama, A.; Kumazawa, R.; Lee, J. H.; López-Bruna, D.; Makino, R.; Masuzaki, S.; Matsumoto, Y.; Matsuura, H.; Mitarai, O.; Miura, H.; Miyazawa, J.; Mizuguchi, N.; Moon, C.; Morita, S.; Moritaka, T.; Mukai, K.; Muroga, T.; Muto, S.; Mutoh, T.; Nagasaka, T.; Nagayama, Y.; Nakajima, N.; Nakamura, Y.; Nakanishi, H.; Nakano, H.; Nakata, M.; Narushima, Y.; Nishijima, D.; Nishimura, A.; Nishimura, S.; Nishitani, T.; Nishiura, M.; Nobuta, Y.; Noto, H.; Nunami, M.; Obana, T.; Ogawa, K.; Ohdachi, S.; Ohno, M.; Ohno, N.; Ohtani, H.; Okamoto, M.; Oya, Y.; Ozaki, T.; Peterson, B. J.; Preynas, M.; Sagara, S.; Saito, K.; Sakaue, H.; Sanpei, A.; Satake, S.; Sato, M.; Saze, T.; Schmitz, O.; Seki, R.; Seki, T.; Sharov, I.; Shimizu, A.; Shiratani, M.; Shoji, M.; Skinner, C.; Soga, R.; Stange, T.; Suzuki, C.; Suzuki, Y.; Takada, S.; Takahata, K.; Takayama, A.; Takayama, S.; Takemura, Y.; Takeuchi, Y.; Tamura, H.; Tamura, N.; Tanaka, H.; Tanaka, K.; Tanaka, M.; Tanaka, T.; Tanaka, Y.; Toda, S.; Todo, Y.; Toi, K.; Toida, M.; Tokitani, M.; Tokuzawa, T.; Tsuchiya, H.; Tsujimura, T.; Tsumori, K.; Usami, S.; Velasco, J. L.; Wang, H.; Watanabe, T.-H.; Watanabe, T.; Yagi, J.; Yajima, M.; Yamada, H.; Yamada, I.; Yamagishi, O.; Yamaguchi, N.; Yamamoto, Y.; Yanagi, N.; Yasuhara, R.; Yatsuka, E.; Yoshida, N.; Yoshinuma, M.; Yoshimura, S.; Yoshimura, Y.

2017-10-01

As the finalization of a hydrogen experiment towards the deuterium phase, the exploration of the best performance of hydrogen plasma was intensively performed in the large helical device. High ion and electron temperatures, T i and T e, of more than 6 keV were simultaneously achieved by superimposing high-power electron cyclotron resonance heating onneutral beam injection (NBI) heated plasma. Although flattening of the ion temperature profile in the core region was observed during the discharges, one could avoid degradation by increasing the electron density. Another key parameter to present plasma performance is an averaged beta value ≤ft< β \\right> . The high ≤ft< β \\right> regime around 4% was extended to an order of magnitude lower than the earlier collisional regime. Impurity behaviour in hydrogen discharges with NBI heating was also classified with a wide range of edge plasma parameters. The existence of a no impurity accumulation regime, where the high performance plasma is maintained with high power heating  >10 MW, was identified. Wide parameter scan experiments suggest that the toroidal rotation and the turbulence are the candidates for expelling impurities from the core region.

Studies of Atomic Free Radicals Stored in a Cryogenic Environment

NASA Technical Reports Server (NTRS)

Lee, David M.; Hubbard, Dorthy (Technical Monitor); Alexander, Glen (Technical Monitor)

2003-01-01

Impurity-Helium Solids are porous gel-like solids consisting of impurity atoms and molecules surrounded by thin layers of solid helium. They provide an ideal medium for matrix isolation of free radicals to prevent recombination and store chemical energy. In this work electron spin resonance, nuclear magnetic resonance, X-ray diffraction, and ultrasound techniques have all been employed to study the properties of these substances. Detailed studies via electron spin resonance of exchange tunneling chemical reactions involving hydrogen and deuterium molecular and atomic impurities in these solids have been performed and compared with theory. Concentrations of hydrogen approaching the quantum solid criterion have been produced. Structured studies involving X ray diffraction, ultrasound, and electron spin resonance have shown that the impurities in impurity helium solids are predominantly contained in impurity clusters, with each cluster being surrounded by thin layers of solid helium.

Full-f XGC1 gyrokinetic study of improved ion energy confinement from impurity stabilization of ITG turbulence

NASA Astrophysics Data System (ADS)

Kim, Kyuho; Kwon, Jae-Min; Chang, C. S.; Seo, Janghoon; Ku, S.; Choe, W.

2017-06-01

Flux-driven full-f gyrokinetic simulations are performed to study carbon impurity effects on the ion temperature gradient (ITG) turbulence and ion thermal transport in a toroidal geometry. Employing the full-f gyrokinetic code XGC1, both main ions and impurities are evolved self-consistently including turbulence and neoclassical physics. It is found that the carbon impurity profile self-organizes to form an inwardly peaked density profile, which weakens the ITG instabilities and reduces the overall fluctuations and ion thermal transport. A stronger reduction appears in the low frequency components of the fluctuations. The global structure of E × B flow also changes, resulting in the reduction of global avalanche like transport events in the impure plasma. Detailed properties of impurity transport are also studied, and it is revealed that both the inward neoclassical pinch and the outward turbulent transport are equally important in the formation of the steady state impurity profile.

Automated statistical experimental design approach for rapid separation of coenzyme Q10 and identification of its biotechnological process related impurities using UHPLC and UHPLC-APCI-MS.

PubMed

Talluri, Murali V N Kumar; Kalariya, Pradipbhai D; Dharavath, Shireesha; Shaikh, Naeem; Garg, Prabha; Ramisetti, Nageswara Rao; Ragampeta, Srinivas

2016-09-01

A novel ultra high performance liquid chromatography method development strategy was ameliorated by applying quality by design approach. The developed systematic approach was divided into five steps (i) Analytical Target Profile, (ii) Critical Quality Attributes, (iii) Risk Assessments of Critical parameters using design of experiments (screening and optimization phases), (iv) Generation of design space, and (v) Process Capability Analysis (Cp) for robustness study using Monte Carlo simulation. The complete quality-by-design-based method development was made automated and expedited by employing sub-2 μm particles column with an ultra high performance liquid chromatography system. Successful chromatographic separation of the Coenzyme Q10 from its biotechnological process related impurities was achieved on a Waters Acquity phenyl hexyl (100 mm × 2.1 mm, 1.7 μm) column with gradient elution of 10 mM ammonium acetate buffer (pH 4.0) and a mixture of acetonitrile/2-propanol (1:1) as the mobile phase. Through this study, fast and organized method development workflow was developed and robustness of the method was also demonstrated. The method was validated for specificity, linearity, accuracy, precision, and robustness in compliance to the International Conference on Harmonization, Q2 (R1) guidelines. The impurities were identified by atmospheric pressure chemical ionization-mass spectrometry technique. Further, the in silico toxicity of impurities was analyzed using TOPKAT and DEREK software. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Out of equilibrium transport through an Anderson impurity: probing scaling laws within the equation of motion approach.

PubMed

Balseiro, C A; Usaj, G; Sánchez, M J

2010-10-27

We study non-equilibrium electron transport through a quantum impurity coupled to metallic leads using the equation of motion technique at finite temperature T. Assuming that the interactions are taking place solely in the impurity and focusing on the infinite Hubbard limit, we compute the out of equilibrium density of states and the differential conductance G(2)(T, V) in order to test several scaling laws. We find that G(2)(T, V)/G(2)(T, 0) is a universal function of both eV/T(K) and T/T(K), T(K) being the Kondo temperature. The effect of an in-plane magnetic field on the splitting of the zero bias anomaly in the differential conductance is also analyzed. For a Zeeman splitting Δ, the computed differential conductance peak splitting depends only on Δ/T(K), and for large fields approaches the value of 2Δ. Besides studying the traditional two leads setup, we also consider other configurations that mimic recent experiments, namely, an impurity embedded in a mesoscopic wire and the presence of a third weakly coupled lead. In these cases, a double peak structure of the Kondo resonance is clearly obtained in the differential conductance while the amplitude of the highest peak is shown to decrease as ln(eV/T(K)). Several features of these results are in qualitative agreement with recent experimental observations reported on quantum dots.

Impurity confinement and transport in high confinement regimes without edge localized modes on DIII-D [Impurity confinement and transport in high confinement regimes without ELMs on DIII-D

DOE PAGES

Grierson, Brian A.; Burrell, Keith H.; Nazikian, Raffi M.; ...

2015-04-17

Here, impurity transport in the DIII-D tokamak is investigated in stationary high confinement (H-mode) regimes without edge localized modes (ELMs). In plasmas maintained by resonant magnetic perturbation (RMP) ELM-suppression and QH-mode the confinement time of fluorine (Z=9) is equivalent to that in ELMing discharges with 40 Hz ELMs. For selected discharges with impurity injection the impurity particle confinement time compared to the energy confinement time is in the range of τ p/τ e ≈ 2 $-$ 3. In QH-mode operation the impurity confinement time is shown to be smaller for intense, coherent magnetic and density fluctuations of the edge harmonicmore » oscillation than weaker fluctuations. Transport coefficients are derived from the time evolution of the impurity density profile and compared to neoclassical and turbulent transport models NEO and TGLF. Neoclassical transport of fluorine is found to be small compared to the experimental values. In the ELMing and RMP ELM-suppressed plasma the impurity transport is affected by the presence of tearing modes. For radii larger than the mode radius the TGLF diffusion coefficient is smaller than the experimental value by a factor of 2-3, while the convective velocity is within error estimates. Low levels of diffusion are observed for radii smaller than the tearing mode radius. In the QH-mode plasma investigated, the TGLF diffusion coefficient higher inside of ρ = 0.4 and lower outside of 0.4 than the experiment, and the TGLF convective velocity is more negative by a factor of approximately 1.7.« less

Argon metastable dynamics and lifetimes in a direct current microdischarge

NASA Astrophysics Data System (ADS)

Stefanović, Ilija; Kuschel, Thomas; Schröter, Sandra; Böke, Marc

2014-09-01

In this paper we study the properties of a pulsed dc microdischarge with the continuous flow of argon. Argon metastable lifetimes are measured by tunable diode laser absorption spectroscopy (TDLAS) and are compared with calculated values which yield information about excitation and de-excitation processes. By increasing the gas flow-rate about 5 times from 10 to 50 sccm, the Arm lifetime increases from 1 to 5 μs due to the reduction of metastable quenching with gas impurities. Optical emission spectroscopy reveals nitrogen and water molecules as the main gas impurities. The estimated N2 density [N2] = 0.1% is too low to explain the measured metastable lifetimes. Water impurity was found to be the main de-excitation source of argon metastable atoms due to high quenching coefficients. The water impurity level of [H2O] = 0.15% to 1% is sufficient to bring calculated metastable lifetimes in line with experiments. The maximum value of water content in the discharge compared to the argon atoms is estimated to approximately 6%, due to the large surface to volume ratio of the microdischarge. The current pulse releases the water molecules from the electrode surface and they are either re-adsorbed in the time between 0.4 ms for [H2O] = 1% and 2.6 ms for [H2O] = 0.15% or pumped out of the discharge with the speed equal to the gas flow-rate. Depending on its partial pressure, the water impurity re-adsorption time is of the order of magnitude or less then the argon gas residence time.

High-Pressure Turbulent Flame Speeds and Chemical Kinetics of Syngas Blends with and without Impurities

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

Peterson, Eric; Mathieu, Olivier; Morones, Anibal

2014-12-01

This Topical Report documents the first year of the project, from October 1, 2013 through September 30, 2014. Efforts for this project included experiments to characterize the atmospheric-pressure turbulent flame speed vessel over a range of operating conditions (fan speeds and turbulent length scales). To this end, a new LDV system was acquired and set up for the detailed characterization of the turbulence field. Much progress was made in the area of impurity kinetics, which included a numerical study of the effect of impurities such as NO2, NO, H2S, and NH3 on ignition delay times and laminar flame speeds ofmore » syngas blends at engine conditions. Experiments included a series of laminar flame speed measurements for syngas (CO/H2) blends with various levels of CH4 and C2H6 addition, and the results were compared to the chemical kinetics model of NUI Galway. Also, a final NOx kinetics mechanism including ammonia was assembled, and a journal paper was written and is now in press. Overall, three journal papers and six conference papers related to this project were published this year. Finally, much progress was made on the design of the new high-pressure turbulent flame speed facility. An overall design that includes a venting system was decided upon, and the detailed design is in progress.« less

Binding energy and photoionization cross-section of hydrogen-like donor impurity in strongly oblate ellipsoidal quantum dot

NASA Astrophysics Data System (ADS)

Hayrapetyan, D. B.; Ohanyan, G. L.; Baghdasaryan, D. A.; Sarkisyan, H. A.; Baskoutas, S.; Kazaryan, E. M.

2018-01-01

Hydrogen-like donor impurity states in strongly oblate ellipsoidal quantum dot have been studied. The hydrogen-like donor impurity states are investigated within the framework of variational method. The trial wave function constructed on the base of wave functions of the system without impurity. The dependence of the energy and binding energy for the ground and first excited states on the geometrical parameters of the ellipsoidal quantum dot and on the impurity position have been calculated. The behavior of the oscillator strength for different angles of incident light and geometrical parameters have been revealed. Photoionization cross-section of the electron transitions from the impurity ground state to the size-quantized ground and first excited states have been studied. The effects of impurity position and the geometrical parameters of the ellipsoidal quantum dot on the photoionization cross section dependence on the photon energy have been considered.

Fabrication of Gate-tunable Graphene Devices for Scanning Tunneling Microscopy Studies with Coulomb Impurities

PubMed Central

Jung, Han Sae; Tsai, Hsin-Zon; Wong, Dillon; Germany, Chad; Kahn, Salman; Kim, Youngkyou; Aikawa, Andrew S.; Desai, Dhruv K.; Rodgers, Griffin F.; Bradley, Aaron J.; Velasco, Jairo; Watanabe, Kenji; Taniguchi, Takashi; Wang, Feng; Zettl, Alex; Crommie, Michael F.

2015-01-01

Owing to its relativistic low-energy charge carriers, the interaction between graphene and various impurities leads to a wealth of new physics and degrees of freedom to control electronic devices. In particular, the behavior of graphene’s charge carriers in response to potentials from charged Coulomb impurities is predicted to differ significantly from that of most materials. Scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) can provide detailed information on both the spatial and energy dependence of graphene's electronic structure in the presence of a charged impurity. The design of a hybrid impurity-graphene device, fabricated using controlled deposition of impurities onto a back-gated graphene surface, has enabled several novel methods for controllably tuning graphene’s electronic properties.1-8 Electrostatic gating enables control of the charge carrier density in graphene and the ability to reversibly tune the charge2 and/or molecular5 states of an impurity. This paper outlines the process of fabricating a gate-tunable graphene device decorated with individual Coulomb impurities for combined STM/STS studies.2-5 These studies provide valuable insights into the underlying physics, as well as signposts for designing hybrid graphene devices. PMID:26273961

Development of Impurity Profiling Methods Using Modern Analytical Techniques.

PubMed

Ramachandra, Bondigalla

2017-01-02

This review gives a brief introduction about the process- and product-related impurities and emphasizes on the development of novel analytical methods for their determination. It describes the application of modern analytical techniques, particularly the ultra-performance liquid chromatography (UPLC), liquid chromatography-mass spectrometry (LC-MS), high-resolution mass spectrometry (HRMS), gas chromatography-mass spectrometry (GC-MS) and high-performance thin layer chromatography (HPTLC). In addition to that, the application of nuclear magnetic resonance (NMR) spectroscopy was also discussed for the characterization of impurities and degradation products. The significance of the quality, efficacy and safety of drug substances/products, including the source of impurities, kinds of impurities, adverse effects by the presence of impurities, quality control of impurities, necessity for the development of impurity profiling methods, identification of impurities and regulatory aspects has been discussed. Other important aspects that have been discussed are forced degradation studies and the development of stability indicating assay methods.

Impurity rejection in the crystallization of ABT-510 as a method to establish starting material specifications.

PubMed

Tolle, John C; Becker, Calvin L; Califano, Jean C; Chang, Jane L; Gernhardt, Kevin; Napier, James J; Wittenberger, Steven J; Yuan, Judy

2009-01-01

Understanding impurity rejection in a drug substance crystallization process is valuable for establishing purity specifications for the starting materials used in the process. Impurity rejection has been determined for all known ABT-510 impurities and for many of the reasonable & conceivable impurities. Based on this study, a very high purity specification (e.g., > 99.7%) can be set for ABT-510 with a high level of confidence.

Impurity effects in crystal growth from solutions: Steady states, transients and step bunch motion

NASA Astrophysics Data System (ADS)

Ranganathan, Madhav; Weeks, John D.

2014-05-01

We analyze a recently formulated model in which adsorbed impurities impede the motion of steps in crystals grown from solutions, while moving steps can remove or deactivate adjacent impurities. In this model, the chemical potential change of an atom on incorporation/desorption to/from a step is calculated for different step configurations and used in the dynamical simulation of step motion. The crucial difference between solution growth and vapor growth is related to the dependence of the driving force for growth of the main component on the size of the terrace in front of the step. This model has features resembling experiments in solution growth, which yields a dead zone with essentially no growth at low supersaturation and the motion of large coherent step bunches at larger supersaturation. The transient behavior shows a regime wherein steps bunch together and move coherently as the bunch size increases. The behavior at large line tension is reminiscent of the kink-poisoning mechanism of impurities observed in calcite growth. Our model unifies different impurity models and gives a picture of nonequilibrium dynamics that includes both steady states and time dependent behavior and shows similarities with models of disordered systems and the pinning/depinning transition.

Impurity bound states in d-wave superconductors with subdominant order parameters

NASA Astrophysics Data System (ADS)

Mashkoori, Mahdi; Björnson, Kristofer; Black-Schaffer, Annica

Single magnetic impurity induces intra-gap bound states in conventional s-wave superconductors (SCs) but, in d-wave SCs only virtual bound states can be induced. However, in small cuprate islands a fully gapped spectrum has recently been discovered. In this work, we investigate the real bound states due to potential and magnetic impurities in the two candidate fully gapped states for this system: the topologically trivial d + is -wave state and the topologically non-trivial d + id' -wave (chiral d-wave state). Using the analytic T-matrix formalism and self-consistent numerical tight-binding lattice calculations, we show that potential and magnetic impurities create entirely different intra-gap bound states in d + is -wave and chiral d-wave SCs. Therefore, our results suggest that the bound states mainly depend on the subdominant order parameter. Considering that recent experiments have demonstrated an access to adjustable coupling J, impurities thus offer an intriguing way to clearly distinguish between the chiral d-wave and topologically trivial d + is -wave state. This work was supported by Swedish Research Council, Swedish Foundation for Strategic Research, the Wallenberg Academy Fellows program and the Göran Gustafsson Foundation. The computations were performed on resources provided by SNIC at LUNARC.

Spin-dependent tunneling recombination in heterostructures with a magnetic layer

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

Denisov, K. S., E-mail: denisokonstantin@gmail.com; Rozhansky, I. V.; Averkiev, N. S.

We propose a mechanism for the generation of spin polarization in semiconductor heterostructures with a quantum well and a magnetic impurity layer spatially separated from it. The spin polarization of carriers in a quantum well originates from spin-dependent tunneling recombination at impurity states in the magnetic layer, which is accompanied by a fast linear increase in the degree of circular polarization of photoluminescence from the quantum well. Two situations are theoretically considered. In the first case, resonant tunneling to the spin-split sublevels of the impurity center occurs and spin polarization is caused by different populations of resonance levels in themore » quantum well for opposite spin projections. In the second, nonresonant case, the spin-split impurity level lies above the occupied states of electrons in the quantum well and plays the role of an intermediate state in the two-stage coherent spin-dependent recombination of an electron from the quantum well and a hole in the impurity layer. The developed theory allows us to explain both qualitatively and quantitatively the kinetics of photoexcited electrons in experiments with photoluminescence with time resolution in Mn-doped InGaAs heterostructures.« less

Floquet theory of microwave absorption by an impurity in the two-dimensional electron gas

NASA Astrophysics Data System (ADS)

Chepelianskii, Alexei D.; Shepelyansky, Dima L.

2018-03-01

We investigate the dynamics of a two-dimensional electron gas (2DEG) under circular polarized microwave radiation in the presence of dilute localized impurities. Inspired by recent developments on Floquet topological insulators we obtain the Floquet wave functions of this system which allow us to predict the microwave absorption and charge density responses of the electron gas; we demonstrate how these properties can be understood from the underlying semiclassical dynamics even for impurities with a size of around a magnetic length. The charge density response takes the form of a rotating charge density vortex around the impurity that can lead to a significant renormalization of the external microwave field which becomes strongly inhomogeneous on the scale of a cyclotron radius around the impurity. We show that this inhomogeneity can suppress the circular polarization dependence which is theoretically expected for microwave induced resistance oscillations but which was not observed in experiments on semiconducting 2DEGs. Our explanation for this so far unexplained polarization independence has close similarities with the Azbel'-Kaner effect in metals where the interaction length between the microwave field and conduction electrons is much smaller than the cyclotron radius due to skin effect generating harmonics of the cyclotron resonance.

Effect of impurities and processing on silicon solar cells. Volume 1: Characterization methods for impurities in silicon and impurity effects data base

NASA Technical Reports Server (NTRS)

Hopkins, R. H.; Davis, J. R.; Rohatgi, A.; Campbell, R. B.; Blais, P. D.; Rai-Choudhury, P.; Stapleton, R. E.; Mollenkopf, H. C.; Mccormick, J. R.

1980-01-01

Two major topics are treated: methods to measure and evaluate impurity effects in silicon and comprehensive tabulations of data derived during the study. Discussions of deep level spectroscopy, detailed dark I-V measurements, recombination lifetime determination, scanned laser photo-response, conventional solar cell I-V techniques, and descriptions of silicon chemical analysis are presented and discussed. The tabulated data include lists of impurity segregation coefficients, ingot impurity analyses and estimated concentrations, typical deep level impurity spectra, photoconductive and open circuit decay lifetimes for individual metal-doped ingots, and a complete tabulation of the cell I-V characteristics of nearly 200 ingots.

A pharmacology guided approach for setting limits on product-related impurities for bispecific antibody manufacturing.

PubMed

Rajan, Sharmila; Sonoda, Junichiro; Tully, Timothy; Williams, Ambrose J; Yang, Feng; Macchi, Frank; Hudson, Terry; Chen, Mark Z; Liu, Shannon; Valle, Nicole; Cowan, Kyra; Gelzleichter, Thomas

2018-04-13

bFKB1 is a humanized bispecific IgG1 antibody, created by conjoining an anti-Fibroblast Growth Factor Receptor 1 (FGFR1) half-antibody to an anti-Klothoβ (KLB) half-antibody, using the knobs-into-holes strategy. bFKB1 acts as a highly selective agonist for the FGFR1/KLB receptor complex and is intended to ameliorate obesity-associated metabolic defects by mimicking the activity of the hormone FGF21. An important aspect of the biologics product manufacturing process is to establish meaningful product specifications regarding the tolerable levels of impurities that copurify with the drug product. The aim of the current study was to determine acceptable levels of product-related impurities for bFKB1. To determine the tolerable levels of these impurities, we dosed obese mice with bFKB1 enriched with various levels of either HMW impurities or anti-FGFR1-related impurities, and measured biomarkers for KLB-independent FGFR1 signaling. Here, we show that product-related impurities of bFKB1, in particular, high molecular weight (HMW) impurities and anti-FGFR1-related impurities, when purposefully enriched, stimulate FGFR1 in a KLB-independent manner. By taking this approach, the tolerable levels of product-related impurities were successfully determined. Our study demonstrates a general pharmacology-guided approach to setting a product specification for a bispecific antibody whose homomultimer-related impurities could lead to undesired biological effects. Copyright © 2018. Published by Elsevier Inc.

High-purity silicon for solar cell applications

NASA Technical Reports Server (NTRS)

Dosaj, V. D.; Hunt, L. P.; Schei, A.

1978-01-01

The article discusses the production of solar cells from high-purity silicon. The process consists of reducing the level of impurities in the raw materials, preventing material contamination before and after entering the furnace, and performing orders-of-magnitude reduction of metal impurity concentrations. The high-purity raw materials are considered with reference to carbon reductants, silica, and graphite electrodes. Attention is also given to smelting experiments used to demonstrate, in an experimental-scale furnace, the production of high-purity SoG-Si. It is found that high-purity silicon may be produced from high-purity quartz and chemically purified charcoal in a 50-kVA arc furnace. The major contamination source is shown to be impurities from the carbon reducing materials.

Complementary Response of Static Spin-Stripe Order and Superconductivity to Nonmagnetic Impurities in Cuprates

DOE PAGES

Guguchia, Z.; Roessli, B.; Khasanov, R.; ...

2017-08-22

Here, we report muon-spin rotation and neutron-scattering experiments on nonmagnetic Zn impurity effects on the static spin-stripe order and superconductivity of the La214 cuprates. Remarkably, it was found that, for samples with hole doping x≈1/8, the spin-stripe ordering temperature T so decreases linearly with Zn doping y and disappears at y≈4%, demonstrating a high sensitivity of static spin-stripe order to impurities within a CuO 2 plane. Moreover, Tso is suppressed by Zn in the same manner as the superconducting transition temperature Tc for samples near optimal hole doping. This surprisingly similar sensitivity suggests that the spin-stripe order is dependent onmore » intertwining with superconducting correlations.« less

Complementary Response of Static Spin-Stripe Order and Superconductivity to Nonmagnetic Impurities in Cuprates

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

Guguchia, Z.; Roessli, B.; Khasanov, R.

Here, we report muon-spin rotation and neutron-scattering experiments on nonmagnetic Zn impurity effects on the static spin-stripe order and superconductivity of the La214 cuprates. Remarkably, it was found that, for samples with hole doping x≈1/8, the spin-stripe ordering temperature T so decreases linearly with Zn doping y and disappears at y≈4%, demonstrating a high sensitivity of static spin-stripe order to impurities within a CuO 2 plane. Moreover, Tso is suppressed by Zn in the same manner as the superconducting transition temperature Tc for samples near optimal hole doping. This surprisingly similar sensitivity suggests that the spin-stripe order is dependent onmore » intertwining with superconducting correlations.« less

Calculation of low-Z impurity pellet induced fluxes of charge exchange neutral particles escaping from magnetically confined toroidal plasmas.

PubMed

Goncharov, P R; Ozaki, T; Sudo, S; Tamura, N; Tolstikhina, I Yu; Sergeev, V Yu

2008-10-01

Measurements of energy- and time-resolved neutral hydrogen and helium fluxes from an impurity pellet ablation cloud, referred to as pellet charge exchange or PCX experiments, can be used to study local fast ion energy distributions in fusion plasmas. The estimation of the local distribution function f(i)(E) of fast ions entering the cloud requires knowledge of both the fraction F(0)(E) of incident ions exiting the cloud as neutral atoms and the attenuation factor A(E,rho) describing the loss of fast atoms in the plasma. Determination of A(E,rho), in turn, requires the total stopping cross section sigma(loss) of neutral atoms in the plasma and the Jacobian reflecting the measurement geometry and the magnetic surface shape. The obtained functions F(0)(E) and A(E,rho) enter multiplicatively into the probability density for escaping neutral particle kinetic energy. A general calculation scheme has been developed and realized as a FORTRAN code, which is to be applied for the calculation of f(i)(E) from PCX experimental results obtained with low-Z impurity pellets.

Fano-shaped impurity spectral density, electric-field-induced in-gap state, and local magnetic moment of an adatom on trilayer graphene

NASA Astrophysics Data System (ADS)

Zhang, Zu-Quan; Li, Shuai; Lü, Jing-Tao; Gao, Jin-Hua

2017-08-01

Recently, the existence of local magnetic moment in a hydrogen adatom on graphene was confirmed experimentally [González-Herrero et al., Science 352, 437 (2016), 10.1126/science.aad8038]. Inspired by this breakthrough, we theoretically investigate the top-site adatom on trilayer graphene (TLG) by solving the Anderson impurity model via self-consistent mean field method. The influence of the stacking order, the adsorption site, and external electric field are carefully considered. We find that, due to its unique electronic structure, the situation of TLG is drastically different from that of the monolayer graphene. First, the adatom on rhombohedral stacked TLG (r-TLG) can have a Fano-shaped impurity spectral density, instead of the normal Lorentzian-like one, when the impurity level is around the Fermi level. Second, the impurity level of the adatom on r-TLG can be tuned into an in-gap state by an external electric field, which strongly depends on the direction of the applied electric field and can significantly affect the local magnetic moment formation. Finally, we systematically calculate the impurity magnetic phase diagrams, considering various stacking orders, adsorption sites, doping, and electric field. We show that, because of the in-gap state, the impurity magnetic phase of r-TLG will obviously depend on the direction of the applied electric field as well. All our theoretical results can be readily tested in experiment, and may give a comprehensive understanding about the local magnetic moment of an adatom on TLG.

Heavy impurity confinement in hybrid operation scenario plasmas with a rotating 1/1 continuous mode

NASA Astrophysics Data System (ADS)

Raghunathan, M.; Graves, J. P.; Nicolas, T.; Cooper, W. A.; Garbet, X.; Pfefferlé, D.

2017-12-01

In future tokamaks like ITER with tungsten walls, it is imperative to control tungsten accumulation in the core of operational plasmas, especially since tungsten accumulation can lead to radiative collapse and disruption. We investigate the behavior of tungsten trace impurities in a JET-like hybrid scenario with both axisymmetric and saturated 1/1 ideal helical core in the presence of strong plasma rotation. For this purpose, we obtain the equilibria from VMEC and use VENUS-LEVIS, a guiding-center orbit-following code, to follow heavy impurity particles. In this work, VENUS-LEVIS has been modified to account for strong plasma flows with associated neoclassical effects arising from such flows. We find that the combination of helical core and plasma rotation augments the standard neoclassical inward pinch compared to axisymmetry, and leads to a strong inward pinch of impurities towards the magnetic axis despite the strong outward diffusion provided by the centrifugal force, as frequently observed in experiments.

Measurement of trace impurities in ultra pure hydrogen and deuterium at the parts-per-billion level using gas chromatography

NASA Astrophysics Data System (ADS)

Ganzha, V.; Ivshin, K.; Kammel, P.; Kravchenko, P.; Kravtsov, P.; Petitjean, C.; Trofimov, V.; Vasilyev, A.; Vorobyov, A.; Vznuzdaev, M.; Wauters, F.

2018-02-01

A series of muon experiments at the Paul Scherrer Institute in Switzerland deploy ultra-pure hydrogen active targets. A new gas impurity analysis technique was developed, based on conventional gas chromatography, with the capability to measure part-per-billion (ppb) traces of nitrogen and oxygen in hydrogen and deuterium. Key ingredients are a cryogenic admixture accumulation, a directly connected sampling system and a dedicated calibration setup. The dependence of the measured concentration on the sample volume was investigated, confirming that all impurities from the sample gas are collected in the accumulation column and measured with the gas chromatograph. The system was calibrated utilizing dynamic dilution of admixtures into the gas flow down to sub-ppb level concentrations. The total amount of impurities accumulated in the purification system during a three month long experimental run was measured and agreed well with the calculated amount based on the measured concentrations in the flow.

High-Pressure Turbulent Flame Speeds and Chemical Kinetics of Syngas Blends with and without Impurities

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

Petersen, Eric; Mathieu, Olivier; Morones, Anibal

This Final Report documents the entire four years of the project, from October 1, 2013 through September 30, 2017. This project was concerned with the chemical kinetics of fuel blends with high-hydrogen content in the presence of impurities. Emphasis was also on the design and construction of a new, high-pressure turbulent flame speed facility and the use of ignition delay times and flame speeds to elucidate the diluent and impurity effects on the fuel chemistry at gas turbine engine conditions and to also validate the chemical kinetics models. The project was divided into five primary tasks: 1) Project Management andmore » Program Planning; 2) Turbulent Flame Speed Measurements at Atmospheric Pressure; 3) Experiments and Kinetics of Syngas Blends with Impurities; 4) Design and Construction of a High-Pressure Turbulent Flame Speed Facility; and 5) High-Pressure Turbulent Flame Speed Measurements. Details on the execution and results of each of these tasks are provided in the main report.« less

Trapped one-dimensional ideal Fermi gas with a single impurity

NASA Astrophysics Data System (ADS)

Astrakharchik, G. E.; Brouzos, I.

2013-08-01

Ground-state properties of a single impurity in a one-dimensional Fermi gas are investigated in uniform and trapped geometries. The energy of a trapped system is obtained (i) by generalizing the McGuire expression from a uniform to trapped system (ii) within the local density approximation (iii) using the perturbative approach in the case of a weakly interacting impurity and (iv) diffusion Monte Carlo method. We demonstrate that there is a closed formula based on the exact solution of the homogeneous case which provides a precise estimation for the energy of a trapped system even for a small number of fermions and arbitrary coupling constant of the impurity. Using this expression, we analyze energy contributions from kinetic, interaction, and potential components, as well as spatial properties such as the system size and the pair-correlation function. Finally, we calculate the frequency of the breathing mode. Our analysis is directly connected and applicable to the recent experiments in microtraps.

Impurity migration pattern under RF sheath potential in tokamak and the response of Plasma to RMP

NASA Astrophysics Data System (ADS)

Xiao, Xiaotao; Gui, Bin; Xia, Tianyang; Xu, Xueqiao; Sun, Youwen

2017-10-01

The migration pattern of impurity sputtered from RF guarder limiter, is simulated by a test particle module. The electric potential with RF sheath boundary condition on the guard limiter and the thermal sheath boundary condition on the divertor surface are used. The turbulence transport is implemented by random walk model. It is found the RF sheath potential enhances the impurity percentage lost at low filed side middle plane, and decreases impurity percentage drifting into core region. This beneficial effect is stronger when sheath potential is large. When turbulence transport is strong enough, their migration pattern will be dominated by transport, not by sheath potential. The Resonant Magnetic field Perturbation (RMP) is successfully applied in EAST experiment and the suppression and mitigation effect on ELM is obtained. A two field fluid model is used to simulate the plasma response to RMP in EAST geometry. The current sheet on the resonance surface is obtained initially and the resonant component of radial magnetic field is suppressed there. With plasma rotation, the Alfven resonance occurs and the current is separated into two current sheets. The simulation result will be integrated with the ELM simulations to study the effects of RMP on ELM. Prepared by LLNL under Contract DE-AC52-07NA27344 and the China Natural Science Foundation under Contract No. 11405215, 11505236 and 11675217.

Understanding of impurity poloidal distribution in the edge pedestal by modelling

NASA Astrophysics Data System (ADS)

Rozhansky, V.; Kaveeva, E.; Molchanov, P.; Veselova, I.; Voskoboynikov, S.; Coster, D.; Fable, E.; Puetterich, T.; Viezzer, E.; Kukushkin, A. S.; Kirk, A.; the ASDEX Upgrade Team

2015-07-01

Simulation of an H-mode ASDEX Upgrade shot with boron impurity was done with the B2SOLPS5.2 transport code. Simulation results were compared with the unique experimental data available for the chosen shot: radial density, electron and ion temperature profiles in the equatorial midplanes, radial electric field profile, radial profiles of the parallel velocity of impurities at the low-field side (LFS) and high-field side (HFS), radial density profiles of impurity ions at LHS and HFS. Simulation results reproduce all available experimental data simultaneously. In particular strong poloidal HFS-LFS asymmetry of B5+ ions was predicted in accordance with the experiment. The simulated HFS B5+ density inside the edge transport barrier is twice larger than that at LFS. This is consistent with the experimental observations where even larger impurity density asymmetry was observed. A similar effect was predicted in the simulation done for the MAST H-mode. Here the HFS density of He2+ is predicted to be 4 times larger than that at LHS. Such a large predicted asymmetry is connected with a larger ratio of HFS and LFS magnetic fields which is typical for spherical tokamaks. The HFS/LFS asymmetry was not measured in the experiment, however modelling qualitatively reproduces the observed change of sign of He+parallel velocity to the counter-current direction at LFS. The understanding of the asymmetry is based on neoclassical effects in plasma with strong gradients. It is demonstrated that simulation results obtained with account of sources of ionization, realistic geometry and turbulent transport are consistent with the simplified analytical approach. Difference from the standard neoclassical theory is emphasized.

Impurity bound states in mesoscopic topological superconducting loops

NASA Astrophysics Data System (ADS)

Jin, Yan-Yan; Zha, Guo-Qiao; Zhou, Shi-Ping

2018-06-01

We study numerically the effect induced by magnetic impurities in topological s-wave superconducting loops with spin-orbit interaction based on spin-generalized Bogoliubov-de Gennes equations. In the case of a single magnetic impurity, it is found that the midgap bound states can cross the Fermi level at an appropriate impurity strength and the circulating spin current jumps at the crossing point. The evolution of the zero-energy mode can be effectively tuned by the located site of a single magnetic impurity. For the effect of many magnetic impurities, two independent midway or edge impurities cannot lead to the overlap of zero modes. The multiple zero-energy modes can be effectively realized by embedding a single Josephson junction with impurity scattering into the system, and the spin current displays oscillatory feature with increasing the layer thickness.

Atomic and molecular data for metallic impurities in fusion plasmas

NASA Astrophysics Data System (ADS)

Gregory, D. C.

1990-06-01

Representatives from electron-impact and ion-atom research groups reviewed and rated the available data on collision processes, of interest to fusion, involving impurity metals. The best available data were identified and rated for accuracy. Gaps and needs for additional experiments and calculations were noted. Summary articles with the group conclusions and recommendations will be published in a special topical issue of Physica Scripta along with articles on specific related topics by members of the Advisory Group. Laboratories at University College, London, were visited in order to renew contact with the research group there, which is one of the three most active in the United Kingdom in electron collision experiments.

Green's function approach to the Kondo effect in nanosized quantum corrals

NASA Astrophysics Data System (ADS)

Li, Q. L.; Wang, R.; Xie, K. X.; Li, X. X.; Zheng, C.; Cao, R. X.; Miao, B. F.; Sun, L.; Wang, B. G.; Ding, H. F.

2018-04-01

We present a theoretical study of the Kondo effect for a magnetic atom placed inside nanocorrals using Green's function calculations. Based on the standard mapping of the Anderson impurity model to a one-dimensional chain model, we formulate a weak-coupling theory to study the Anderson impurities in a hosting bath with a surface state. With further taking into account the multiple scattering effect of the surrounding atoms, our calculations show that the Kondo resonance width of the atom placed at the center of the nanocorral can be significantly tuned by the corral size, in good agreement with recent experiments [Q. L. Li et al., Phys. Rev. B 97, 035417 (2018), 10.1103/PhysRevB.97.035417]. The method can also be applied to the atom placed at an arbitrary position inside the corral where our calculation shows that the Kondo resonance width also oscillates as the function of its separation from the corral center. The prediction is further confirmed by the low-temperature scanning tunneling microscopy studies where a one-to-one correspondence is found. The good agreement with the experiments validates the generality of the method to the system where multiadatoms are involved.

Impurity-directed transport within a finite disordered lattice

NASA Astrophysics Data System (ADS)

Magnetta, Bradley J.; Ordonez, Gonzalo; Garmon, Savannah

2018-02-01

We consider a finite, disordered 1D quantum lattice with a side-attached impurity. We study theoretically the transport of a single electron from the impurity into the lattice, at zero temperature. The transport is dominated by Anderson localization and, in general, the electron motion has a random character due to the lattice disorder. However, we show that by adjusting the impurity energy the electron can attain quasi-periodic motions, oscillating between the impurity and a small region of the lattice. This region corresponds to the spatial extent of a localized state with an energy matched by that of the impurity. By precisely tuning the impurity energy, the electron can be set to oscillate between the impurity and a region far from the impurity, even distances larger than the Anderson localization length. The electron oscillations result from the interference of hybridized states, which have some resemblance to Pendry's necklace states (Pendry, 1987) [21]. The dependence of the electron motion on the impurity energy gives a potential mechanism for selectively routing an electron towards different regions of a 1D disordered lattice.

Impurities in silicon solar cells

NASA Technical Reports Server (NTRS)

Hopkins, R. H.

1985-01-01

Metallic impurities, both singly and in combinations, affect the performance of silicon solar cells. Czochralski silicon web crystals were grown with controlled additions of secondary impurities. The primary electrical dopants were boron and phosphorus. The silicon test ingots were grown under controlled and carefully monitored conditions from high-purity charge and dopant material to minimize unintentional contamination. Following growth, each crystal was characterized by chemical, microstructural, electrical, and solar cell tests to provide a detailed and internally consistent description of the relationships between silicon impurity concentration and solar cell performance. Deep-level spectroscopy measurements were used to measure impurity concentrations at levels below the detectability of other techniques and to study thermally-induced changes in impurity activity. For the majority of contaminants, impurity-induced performance loss is due to a reduction of the base diffusion length. From these observations, a semi-empirical model which predicts cell performance as a function of metal impurity concentration was formulated. The model was then used successfully to predict the behavior of solar cells bearing as many as 11 different impurities.

Effect of Impurities on the Freezing Point of Zinc

NASA Astrophysics Data System (ADS)

Sun, Jianping; Rudtsch, Steffen; Niu, Yalu; Zhang, Lin; Wang, Wei; Den, Xiaolong

2017-03-01

The knowledge of the liquidus slope of impurities in fixed-point metal defined by the International Temperature Scale of 1990 is important for the estimation of uncertainties and correction of fixed point with the sum of individual estimates method. Great attentions are paid to the effect of ultra-trace impurities on the freezing point of zinc in the National Institute of Metrology. In the present work, the liquidus slopes of Ga-Zn, Ge-Zn were measured with the slim fixed-point cell developed through the doping experiments, and the temperature characteristics of the phase diagram of Fe-Zn were furthermore investigated. A quasi-adiabatic Zn fixed-point cell was developed with the thermometer well surrounded by the crucible with the pure metal, and the temperature uniformity of less than 20 mK in the region where the metal is located was obtained. The previous doping experiment of Pb-Zn with slim fixed-point cell was checked with quasi-adiabatic Zn fixed-point cell, and the result supports the previous liquidus slope measured with the traditional fixed-point realization.

Material Surface Characteristics and Plasma Performance in the Lithium Tokamak Experiment

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

Lucia, Matthew James

The performance of a tokamak plasma and the characteristics of the surrounding plasma facing component (PFC) material surfaces strongly influence each other. Despite this relationship, tokamak plasma physics has historically been studied more thoroughly than PFC surface physics. The disparity is particularly evident in lithium PFC research: decades of experiments have examined the effect of lithium PFCs on plasma performance, but the understanding of the lithium surface itself is much less complete. This latter information is critical to identifying the mechanisms by which lithium PFCs affect plasma performance. This research focused on such plasma-surface interactions in the Lithium Tokamak Experimentmore » (LTX), a spherical torus designed to accommodate solid or liquid lithium as the primary PFC. Surface analysis was accomplished via the novel Materials Analysis and Particle Probe (MAPP) diagnostic system. In a series of experiments on LTX, the MAPP x-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS) capabilities were used for in vacuo interrogation of PFC samples. This represented the first application of XPS and TDS for in situ surface analysis of tokamak PFCs. Surface analysis indicated that the thin (d ~ 100nm) evaporative lithium PFC coatings in LTX were converted to Li2O due to oxidizing agents in both the residual vacuum and the PFC substrate. Conversion was rapid and nearly independent of PFC temperature, forming a majority Li2O surface within minutes and an entirely Li2O surface within hours. However, Li2O PFCs were still capable of retaining hydrogen and sequestering impurities until the Li2O was further oxidized to LiOH, a process that took weeks. For hydrogen retention, Li2O PFCs retained H+ from LTX plasma discharges, but no LiH formation was observed. Instead, results implied that H+ was only weakly-bound, such that it almost completely outgassed as H2 within minutes. For impurity sequestration, LTX plasma performance—ascertained from plasma current and density measurements—progressively improved as plasma carbon and oxygen impurity levels fell. This was true for PFC conditioning by vacuum baking and argon glow discharge cleaning, as well as by lithium evaporation. Some evidence suggested that impurity sequestration was more important than hydrogen retention in enhancing LTX plasma performance. In contrast with expectations for lithium PFCs, heating the Li2O PFCs in LTX caused increased plasma impurity levels that tended to reduce plasma performance.« less

Effects of Convective Solute and Impurity Transport in Protein Crystal Growth

NASA Technical Reports Server (NTRS)

Vekilov, Peter G.; Thomas, Bill R.; Rosenberger, Franz

1998-01-01

High-resolution optical interferometry was used to investigate the effects of forced solution convection on the crystal growth kinetics of the model protein lysozyme. Most experiments were conducted with 99.99% pure protein solutions. To study impurity effects, approx. 1% of lysozyme dimer (covalently bound) was added in some cases. We show that the unsteady kinetics, corresponding to bunching of growth steps, can be characterized by the Fourier components of time traces of the growth rate. Specific Fourier spectra are uniquely determined by the solution conditions (composition, temperature, and flow rate) and the growth layer source activity. We found that the average step velocity and growth rate increase by approx. I0% with increasing flow rate, as a result of the enhanced solute supply to the interface. More importantly, faster convective transport results in lower fluctuation amplitudes. This observation supports our rationale for system-dependent effects of transport on the structural perfection of protein crystals. We also found that solution flow rates greater than 500 microns/s result in stronger fluctuations while the average growth rate is decreased. This can lead to growth cessation at low supersaturations. With the intentionally contaminated solutions, these undesirable phenomena occurred at about half the flow rates required in pure solutions. Thus, we conclude that they are due to enhanced convective supply of impurities that are incorporated into the crystal during growth. Furthermore, we found that the impurity effects are reduced at higher crystal growth rates. Since the exposure time of terraces is inversely proportional to the growth rate, this observation suggests that the increased kinetics instability results from impurity adsorption on the interface. Finally, we provide evidence relating earlier observations of "slow protein crystal growth kinetics" to step bunch formation in response to nonsteady step generation.

Theory of p-type Zinc Oxide

NASA Astrophysics Data System (ADS)

Zhang, Shengbai

2002-03-01

Recent advances in bipolar doping of wide gap semiconductors challenge our understanding of impurity and defect properties in these materials, as theories based on equilibrium thermodynamics cannot keep up with these recent developments. For ZnO, the puzzling experimental results involve doping with nitrogen(M. Joseph, H. Tabata, and T. Kawai, Jpn. J. Appl. Phys. 38), L1205 (1999)., arsenic(Y. R. Ryu, S. Zhu, D. C. Look, J. M. Wrobel, H. M. Jeong, and H. W. White, J. Crys. Growth 216), 330 (2000)., and phosphorus(T. Aoki, Y. Hatanaka, and D. C. Look, Appl. Phys. Lett. 76), 3257 (2000).. In this talk, I will discuss some recent theoretical efforts trying to explain the experiments by first-principles total energy calculations. I will first discuss the acceptor level positions for group I and group V impurities. A general trend is observed(C. H. Park, S. B. Zhang, and S.-H. Wei, submitted to Phys. Rev. B.) that substitutional group V impurities on O range from relatively deep (e.g. N) to very deep (e.g. P and As) with high formation energies, whereas substitutional group I impurities on Zn are shallow acceptors. However, substitutional group I impurities are unstable against the formation of interstitials that are donors. A careful examination of N doping in Ref. [1] suggests that one can kinetically suppress the formation of N2 molecules by engineering dopant sources/footnoteY. Yan, S. B. Zhang, and S. T. Pantelides, Phys. Rev. Lett. 86, 5723 (2001).. This leads to significantly enhanced N solubility and hence p-type ZnO. For As [2], our preliminary studies show that the formation energy of AsO is so high that it is an exothermic process to form low-energy complexes that act effectively as relatively shallow acceptors.

Contaminants in commercial preparations of ‘purified’ small leucine-rich proteoglycans may distort mechanistic studies

PubMed Central

Brown, Sharon J.; Fuller, Heidi R.; Jones, Philip; Caterson, Bruce; Shirran, Sally L.; Botting, Catherine H.

2016-01-01

The present study reports the perplexing results that came about because of seriously impure commercially available reagents. Commercial reagents and chemicals are routinely ordered by scientists and expected to have been rigorously assessed for their purity. Unfortunately, we found this assumption to be risky. Extensive work was carried out within our laboratory using commercially sourced preparations of the small leucine-rich proteoglycans (SLRPs), decorin and biglycan, to investigate their influence on nerve cell growth. Unusual results compelled us to analyse the composition and purity of both preparations of these proteoglycans (PGs) using both mass spectrometry (MS) and Western blotting, with and without various enzymatic deglycosylations. Commercial ‘decorin’ and ‘biglycan’ were found to contain a mixture of PGs including not only both decorin and biglycan but also fibromodulin and aggrecan. The unexpected effects of ‘decorin’ and ‘biglycan’ on nerve cell growth could be explained by these impurities. Decorin and biglycan contain either chondroitin or dermatan sulfate glycosaminoglycan (GAG) chains whereas fibromodulin only contains keratan sulfate and the large (>2500 kDa), highly glycosylated aggrecan contains both keratan and chondroitin sulfate. The different structure, molecular weight and composition of these impurities significantly affected our work and any conclusions that could be made. These findings beg the question as to whether scientists need to verify the purity of each commercially obtained reagent used in their experiments. The implications of these findings are vast, since the effects of these impurities may already have led to inaccurate conclusions and reports in the literature with concomitant loss of researchers’ funds and time. PMID:27994047

User's guide to the Residual Gas Analyzer (RGA)

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

Artman, S.A.

1988-08-04

The Residual Gas Analyzer (RGA), a Model 100C UTI quadrupole mass spectrometer, measures the concentrations of selected masses in the Fusion Energy Division's (FED) Advanced Toroidal Facility (ATF). The RGA software is a VAX FORTRAN computer program which controls the experimental apparatus, records the raw data, performs data reduction, and plots the data. The RGA program allows data to be collected from an RGA on ATF or from either of two RGAs in the laboratory. In the laboratory, the RGA diagnostic plays an important role in outgassing studied on various candidate materials for fusion experiments. One such material, graphite, ismore » being used more often in fusion experiments due to its ability to withstand high power loads. One of the functions of the RGA diagnostic is aid in the determination of the best grade of graphite to be used in these experiments and to study the procedures used to condition it. A procedure of particular interest involves baking the graphite sample in order to remove impurities that may be present in it. These impurities can be studied while in the ATF plasma or while being baked and outgassed in the laboratory. The Residual Gas Analyzer is a quadrupole mass spectrometer capable of scanning masses ranging in size from 1 atomic mass unit (amu) to 300 amu while under computer control. The procedure for collecting data for a particular mass is outlined.« less

Barium Transport Process in Impregnated Dispenser Cathodes.

DTIC Science & Technology

1982-01-25

experiments were carried out on pure tungsten. The tung- sten was either in the form of thin foils (6 mm on a side) or single crystal disks (6 mm in...temperature reveal the presence of car- bon, silicon , calcium, and nitrogen impurities, with only trace amounts (ɚ%) of calcium and nitrogen. Carbon is not...expected to be present at diffusion temperatures but forms as an overlayer only upon cooling [6]. We hope to re- duce silicon impurity levels by use of

Status of the NOAO evaluation of the Hughes 20x64 Si:As impurity band conduction array. [for ground and space-based astronomy

NASA Technical Reports Server (NTRS)

Fowler, A. M.; Joyce, R. R.

1990-01-01

The Hughes 20 x 64 Si:As impurity band conduction arrays designed for ground-based and spaceborne astronomy observations is described together with experiments performed at NOAO to test these arrays. Special attention is given to the design and the characteristics of the test system and to the test methods. The initial tests on two columns of one array indicate that the array is easy to operate and performed satisfactorily.

Monte Carlo method for magnetic impurities in metals

NASA Technical Reports Server (NTRS)

Hirsch, J. E.; Fye, R. M.

1986-01-01

The paper discusses a Monte Carlo algorithm to study properties of dilute magnetic alloys; the method can treat a small number of magnetic impurities interacting wiith the conduction electrons in a metal. Results for the susceptibility of a single Anderson impurity in the symmetric case show the expected universal behavior at low temperatures. Some results for two Anderson impurities are also discussed.

Dynamics of Fermionic Impurity in One Dimension

NASA Astrophysics Data System (ADS)

Guan, Huijie; Andrei, Natan

2014-03-01

We study the dynamics of a fermionic impurity propagating in a one dimensional infinite line. The system is described by the Gaudin-Yang Model and is exactly solvable by the Nested Bethe Ansatz. Starting from a generic initial state, we obtain the time evolution of the wavefunction by the Yudson Approach in which we expand the initial state with the Nested Bethe Ansatz solutions. One situation that we are interested in is where, initially, the impurity is embedded in host fermions with a lattice configuration and one remove the periodic potential at time zero. We calculate the density profile and correlation functions at a later time. Another situation is to shoot an impurity into a cloud of fermions and calculate the probability for it to pass through. While the repulsive case has been studied already[1], we extend it to the attractive case and study the role of bound states in the evolution. We are also interested in boson impurity problem, where not only impurity interacts with host particles, all host particles interact with each other.

Orbital effect of the magnetic field in dynamical mean-field theory

NASA Astrophysics Data System (ADS)

Acheche, S.; Arsenault, L.-F.; Tremblay, A.-M. S.

2017-12-01

The availability of large magnetic fields at international facilities and of simulated magnetic fields that can reach the flux-quantum-per-unit-area level in cold atoms calls for systematic studies of orbital effects of the magnetic field on the self-energy of interacting systems. Here we demonstrate theoretically that orbital effects of magnetic fields can be treated within single-site dynamical mean-field theory with a translationally invariant quantum impurity problem. As an example, we study the one-band Hubbard model on the square lattice using iterated perturbation theory as an impurity solver. We recover the expected quantum oscillations in the scattering rate, and we show that the magnetic fields allow the interaction-induced effective mass to be measured through the single-particle density of states accessible in tunneling experiments. The orbital effect of magnetic fields on scattering becomes particularly important in the Hofstadter butterfly regime.

Trace element analysis of rough diamond by LA-ICP-MS: a case of source discrimination?

PubMed

Dalpé, Claude; Hudon, Pierre; Ballantyne, David J; Williams, Darrell; Marcotte, Denis

2010-11-01

Current profiling of rough diamond source is performed using different physical and/or morphological techniques that require strong knowledge and experience in the field. More recently, chemical impurities have been used to discriminate diamond source and with the advance of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) empirical profiling of rough diamonds is possible to some extent. In this study, we present a LA-ICP-MS methodology that we developed for analyzing ultra-trace element impurities in rough diamond for origin determination ("profiling"). Diamonds from two sources were analyzed by LA-ICP-MS and were statistically classified by accepted methods. For the two diamond populations analyzed in this study, binomial logistic regression produced a better overall correct classification than linear discriminant analysis. The results suggest that an anticipated matrix match reference material would improve the robustness of our methodology for forensic applications. © 2010 American Academy of Forensic Sciences.

Screening of charged impurities as a possible mechanism for conductance change in graphene gas sensing

NASA Astrophysics Data System (ADS)

Liang, Sang-Zi; Chen, Gugang; Harutyunyan, Avetik R.; Sofo, Jorge O.

2014-09-01

In carbon nanotube and graphene gas sensing, the measured conductance change after the sensor is exposed to target molecules has been traditionally attributed to carrier density change due to charge transfer between the sample and the adsorbed molecule. However, this explanation has many problems when it is applied to graphene: The increased amount of Coulomb impurities should lead to decrease in carrier mobility which was not observed in many experiments, carrier density is controlled by the gate voltage in the experimental setup, and there are inconsistencies in the energetics of the charge transfer. In this paper we explore an alternative mechanism. Charged functional groups and dipolar molecules on the surface of graphene may counteract the effect of charged impurities on the substrate. Because scattering of electrons with these charged impurities has been shown to be the limiting factor in graphene conductivity, this leads to significant changes in the transport behavior. A model for the conductivity is established using the random phase approximation dielectric function of graphene and the first-order Born approximation for scattering. The model predicts optimal magnitudes for the charge and dipole moment which maximally screen a given charged impurity. The dipole screening is shown to be generally weaker than the charge screening although the former becomes more effective with higher gate voltage away from the charge neutrality point. The model also predicts that with increasing amount of adsorbates, the charge impurities eventually become saturated and additional adsorption always lead to decreasing conductivity.

Effect of Impurities on the Triple Point of Water: Experiments with Doped Cells at Different Liquid Fractions

NASA Astrophysics Data System (ADS)

Dobre, M.; Peruzzi, A.; Kalemci, M.; Van Geel, J.; Maeck, M.; Uytun, A.

2018-05-01

Recent international comparisons showed that there is still room for improvement in triple point of water (TPW) realization uncertainty. Large groups of cells manufactured, maintained and measured in similar conditions still show a spread in the realized TPW temperature that is larger than the best measurement uncertainties (25 µK). One cause is the time-dependent concentration of dissolved impurities in water. The origin of such impurities is the glass/quartz envelope dissolution during a cell lifetime. The effect is a difference in the triple point temperature proportional to the impurities concentration. In order to measure this temperature difference and to investigate the effect of different types of impurities, we manufactured doped cells with different concentrations of silicon (Si), boron (B), sodium (Na) and potassium (K), the glass main chemical components. To identify any influence of the filling process, two completely independent manufacturing procedures were followed in two different laboratories, both national metrology institutes (VSL, Netherlands and UME, Turkey). Cells glass and filling water were also different while the doping materials were identical. Measuring the temperature difference as a function of the liquid fraction is a method to obtain information about impurities concentrations in TPW. Only cells doped with 1 µmol·mol-1 B, Na and K proved to be suitable for measurements at different liquid fractions. We present here the results with related uncertainties and discuss the critical points in this experimental approach.

Quality by design: a systematic and rapid liquid chromatography and mass spectrometry method for eprosartan mesylate and its related impurities using a superficially porous particle column.

PubMed

Kalariya, Pradipbhai D; Kumar Talluri, Murali V N; Gaitonde, Vinay D; Devrukhakar, Prashant S; Srinivas, Ragampeta

2014-08-01

The present work describes the systematic development of a robust, precise, and rapid reversed-phase liquid chromatography method for the simultaneous determination of eprosartan mesylate and its six impurities using quality-by-design principles. The method was developed in two phases, screening and optimization. During the screening phase, the most suitable stationary phase, organic modifier, and pH were identified. The optimization was performed for secondary influential parameters--column temperature, gradient time, and flow rate using eight experiments--to examine multifactorial effects of parameters on the critical resolution and generated design space representing the robust region. A verification experiment was performed within the working design space and the model was found to be accurate. This study also describes other operating features of the column packed with superficially porous particles that allow very fast separations at pressures available in most liquid chromatography instruments. Successful chromatographic separation was achieved in less than 7 min using a fused-core C18 (100 mm × 2.1 mm, 2.6 μm) column with linear gradient elution of 10 mM ammonium formate (pH 3.0) and acetonitrile as the mobile phase. The method was validated for specificity, linearity, accuracy, precision, and robustness in compliance with the International Conference on Harmonization Q2 (R1) guidelines. The impurities were identified by liquid chromatography with mass spectrometry. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Identification, synthesis, isolation and characterization of new impurity in metoprolol tartrate tablets.

PubMed

Reddy, R Buchi; More, Kishor R; Gupta, Leena; Jha, Mukesh S; Magar, Laki

2016-01-05

A new unknown impurity was observed in accelerated stability studies of Metoprolol tartrate tablets. This impurity has been identified, synthesized and characterized through different spectral studies and confirmed as an adduct of lactose and Metoprolol formed by Maillard reaction. Copyright © 2015 Elsevier B.V. All rights reserved.

Global modelling of plasma-wall interaction in reversed field pinches

NASA Astrophysics Data System (ADS)

Bagatin, M.; Costa, S.; Ortolani, S.

1989-04-01

The impurity production and deuterium recycling mechanisms in ETA—BETA II and RFX are firstly discussed by means of a simple model applicable to a stationary plasma interacting with the wall. This gives the time constant and the saturation values of the impurity concentration as a function of the boundary temperature and density. If the latter is sufficiently high, the impurity buildup in the main plasma becomes to some extent stabilized by the shielding effect of the edge. A self-consistent global model of the time evolution of an RFP plasma interacting with the wall is then described. The bulk and edge parameters are derived by solving the energy and particle balance equations incorporating some of the basic plasma-surface processes, such as sputtering, backscattering and desorption. The application of the model to ETA-BETA II confirms the impurity concentrations of the light and metal impurities as well as the time evolution of the average electron density found experimentally under different conditions. The model is then applied to RFX, a larger RFP experiment under construction, whose wall will be protected by a full graphite armour. The time evolution of the discharge shows that carbon sputtering could increase Zeff to ~ 4, but without affecting significantly the plasma performance.

Numerical modelling of the effect of dry air traces in a helium parallel plate dielectric barrier discharge

NASA Astrophysics Data System (ADS)

Lazarou, C.; Belmonte, T.; Chiper, A. S.; Georghiou, G. E.

2016-10-01

A validated numerical model developed for the study of helium barrier discharges in the presence of dry air impurities is presented in this paper. The model was used to numerically investigate the influence of air traces on the evolution of the helium dielectric barrier discharge (DBD). The level of dry air used as impurity was in the range from 0 to 1500 ppm, which corresponds to the most commonly encountered range in atmospheric pressure discharge experiments. The results presented in this study clearly show that the plasma chemistry and consequently the discharge evolution is highly affected by the concentration level of impurities in the mixture. In particular, it was observed that air traces assist the discharge ignition at low concentration levels (~55 ppm), while on the other hand, they increase the burning voltage at higher concentration levels (~1000 ppm). Furthermore, it was found that the discharge symmetry during the voltage cycle highly depends on the concentration of air. For the interpretation of the results, a detailed analysis of the processes that occur in the discharge gap is performed and the main reaction pathways of ion production are described. Thanks to this approach, useful insight into the physics behind the evolution of the discharge is obtained.

Volatile Impurities in the Plutonium Immobilization Ceramic Wasteform

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

Cozzi, A.D.

1999-10-15

Approximately 18 of the 50 metric tons of plutonium identified for disposition contain significant quantities of impurities. A ceramic waste form is the chosen option for immobilization of the excess plutonium. The impurities associated with the stored plutonium have been identified (CaCl2, MgF2, Pb, etc.). For this study, only volatile species are investigated. The impurities are added individually. Cerium is used as the surrogate for plutonium. Three compositions, including the baseline composition, were used to verify the ability of the ceramic wasteform to accommodate impurities. The criteria for evaluation of the effect of the impurities were the apparent porosity andmore » phase assemblage of sintered pellets.« less

First-Principles Study of Impurities in TlBr

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

Du, Mao-Hua

2012-01-01

TlBr is a promising semiconductor material for room-temperature radiation detection. Material purification has been the driver for the recent improvement in the TlBr detector performance, mainly reflected by the significant increase in the carrier mobility-lifetime product. This suggests that impurities have significant impact on the carrier transport in TlBr. In this paper, first-principles calculations are used to study the properties of a number of commonly observed impurities in TlBr. The impurity-induced gap states are presented and their effects on the carrier trapping are discussed.

First-principles study of impurities in TlBr

NASA Astrophysics Data System (ADS)

Du, Mao-Hua

2012-04-01

TlBr is a promising semiconductor material for room-temperature radiation detection. Material purification has been the driver for the recent improvement in the TlBr detector performance, mainly reflected by the significant increase in the carrier mobility-lifetime product. This suggests that impurities have significant impact on the carrier transport in TlBr. In this paper, first-principles calculations are used to study the properties of a number of commonly observed impurities in TlBr. The impurity-induced gap states are presented and their effects on the carrier trapping are discussed.

Effects of Density and Impurity on Edge Localized Modes in Tokamaks

NASA Astrophysics Data System (ADS)

Zhu, Ping

2017-10-01

Plasma density and impurity concentration are believed to be two of the key elements governing the edge tokamak plasma conditions. Optimal levels of plasma density and impurity concentration in the edge region have been searched for in order to achieve the desired fusion gain and divertor heat/particle load mitigation. However, how plasma density or impurity would affect the edge pedestal stability may have not been well known. Our recent MHD theory modeling and simulations using the NIMROD code have found novel effects of density and impurity on the dynamics of edge-localized modes (ELMs) in tokamaks. First, previous MHD analyses often predict merely a weak stabilizing effect of toroidal flow on ELMs in experimentally relevant regimes. We find that the stabilizing effects on the high- n ELMs from toroidal flow can be significantly enhanced with the increased edge plasma density. Here n denotes the toroidal mode number. Second, the stabilizing effects of the enhanced edge resistivity due to lithium-conditioning on the low- n ELMs in the high confinement (H-mode) discharges in NSTX have been identified. Linear stability analysis of the experimentally constrained equilibrium suggests that the change in the equilibrium plasma density and pressure profiles alone due to lithium-conditioning may not be sufficient for a complete suppression of the low- n ELMs. The enhanced resistivity due to the increased effective electric charge number Zeff after lithium-conditioning provides additional stabilization of the low- n ELMs. These new effects revealed in our theory analyses may help further understand recent ELM experiments and suggest new control schemes for ELM suppression and mitigation in future experiments. They may also pose additional constraints on the optimal levels of plasma density and impurity concentration in the edge region for H-mode tokamak operation. Supported by National Magnetic Confinement Fusion Science Program of China Grants 2014GB124002 and 2015GB101004, the 100 Talent Program of the Chinese Academy of Sciences, and U.S. Department of Energy Grants DE-FG02-86ER53218 and DE-FC02-08ER54975.

a Vacuum Ultraviolet Study of the Alcator C Tokamak Plasma Using a High Resolution, One-Dimensional Photon Counting Detector.

NASA Astrophysics Data System (ADS)

Benjamin, Russell D.

A photon counting detector based on an image intensified photodiode array was developed to meet the needs of one particular area of spectroscopic study, the determination of the kinetic temperature of impurity species. The image intensifier incorporates 3 high strip current ( ~300 muA) microchannel plates in a 'Z' configuration to achieve the gain required for the detection of single photon events. The design, construction, and laboratory testing of this system to determine its suitability for fusion plasma diagnostics is described, in particular, the ability to measure emission line profiles in order to determine the kinetic temperature of the emitting species. The photon counting detector, mounted on the exit plane of a 1m Ebert-Fastie spectrometer, was used to make spectroscopic measurements of the local ion temperature in Alcator C plasmas using impurity emission lines. Alcator experiments on one particular method of RF heating in a tokamak plasma, the launching of Ion Bernstein waves (IBW), are discussed. The O V kinetic temperature increases during IBW injection as the pre-RF plasma density is raised (on a shot-to-shot basis) above the region in which significant increases in the central ion temperature are observed. In addition, ion temperature profiles were measured during Ion Bernstein wave experiments by combining this point derived from the fit to the emission line of O VII with neutral particle analyzer data. The incorporation of the O VII temperature point in the determination of the pre-RF ion temperature profile results in a significant reduction (~0.4 cm) in the characteristic width of this profile. The high resolution and geometric stability of the photon counting detector made possible the measurement of small wavelength shifts (Deltalambda ~ 0.01 A) and, therefore, the determination of small bulk plasma motions (in this case, poloidal rotation of the plasma) through the Doppler shift of impurity emission lines. The Zeeman effect makes a significant contribution to the measured line profile in high field tokamaks, even in the ultraviolet. Modelling of the Zeeman effect is discussed and applied to the impurity species observed in Alcator C plasmas. (Abstract shortened with permission of author.).

Thermal Stability of Nanocrystalline Copper for Potential Use in Printed Wiring Board Applications

NASA Astrophysics Data System (ADS)

Woo, Patrick Kai Fai

Copper is a widely used conductor in the manufacture of printed wiring boards (PWB). The trends in miniaturization of electronic devices create increasing challenges to all electronic industries. In particular PWB manufacturers face great challenges because the increasing demands in greater performance and device miniaturization pose enormous difficulties in manufacturing and product reliability. Nanocrystalline and ultra-fine grain copper can potentially offer increased reliability and functionality of the PWB due to the increases in strength and achievable wiring density by reduction in grain size. The first part of this thesis is concerned with the synthesis and characterization of nanocrystalline and ultra-fine grain-sized copper for potential applications in the PWB industry. Nanocrystalline copper with different amounts of sulfur impurities (25-230ppm) and grain sizes (31-49nm) were produced and their hardness, electrical resistivity and etchability were determined. To study the thermal stability of nanocrystalline copper, differential scanning calorimetry and isothermal heat treatments combined with electron microscopy techniques for microstructural analysis were used. Differential scanning calorimetry was chosen to continuously monitor the grain growth process in the temperature range from 40?C to 400?C. During isothermal annealing experiments samples were annealed at 23?C, 100?C and 300?C to study various potential thermal issues for these materials in PWB applications such as the long-term room temperature thermal stability as well as for temperature excursions above the operation temperature and peak temperature exposure during the PWB manufacturing process. From all annealing experiments the various grain growth events and the overall stability of these materials were analyzed in terms of driving and dragging forces. Experimental evidence is presented which shows that the overall thermal stability, grain boundary character and texture evolution of copper is greatly related to changes in driving and dragging forces, which in turn, are strongly depended on parameters such as annealing temperature and time, total sulfur impurity content and the distribution of the impurities within the material. It was shown that a simple increase in the sulfur impurity level does not necessarily improve the thermal stability of nanocrystalline copper.

Stability of Weyl metals under impurity scattering

NASA Astrophysics Data System (ADS)

Huang, Zhoushen; Das, Tanmoy; Balatsky, Alexander V.; Arovas, Daniel P.

2013-04-01

We investigate the effects of bulk impurities on the electronic spectrum of Weyl semimetals, a recently identified class of Dirac-type materials. Using a T-matrix approach, we study resonant scattering due to a localized impurity in tight-binding versions of the continuum models recently discussed by [Burkov, Hook, and Balents, Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.84.235126 84, 235126 (2011)], describing perturbed four-component Dirac fermions in the vicinity of a critical point. The impurity potential is described by a strength g as well as a matrix structure Λ. Unlike the case in d-wave superconductors, where a zero energy resonance can always be induced by varying the scalar and/or magnetic impurity strength, we find that for certain types of impurity (Λ), the Weyl node is protected and that a scalar impurity will induce an intragap resonance over a wide range of scattering strength. A general framework is developed to address this question, as well as to determine the dependence of resonance energy on the impurity strength.

Adsorption mechanisms of the nonequilibrium incorporation of admixtures in a growing crystal

NASA Astrophysics Data System (ADS)

Franke, V. D.; Punin, Yu. O.; Smetannikova, O. G.; Kenunen, D. S.

2007-12-01

The nonequilibrium partition of components between a crystal and solution is mainly controlled by impurity adsorption on the surface of the growing crystal. The specificity of adsorption on the faces of various simple forms leads to the sectorial zoning of crystals. This effect was studied experimentally for several crystallizing systems with different impurities, including isomorphous, 2d-isomorphous, and nonisomorphous, readily adsorbed impurities. In all systems, the sectorial selectivity of impurity incorporation into host crystals has been detected with partition coefficients many times higher than in the case of equilibrium partition. Specific capture of impurities by certain faces is accompanied by inhibition of their growth and modification of habit. The decrease in nonequilibrium partition coefficients with degree of oversaturation provides entrapment of impurities in the growing crystals. Thereby, the adsorption mechanism works in much the same mode for impurities of quite different nature. The behavior of partition coefficient differs drastically from impurity capturing by diffusion mechanism.

Non-linear optical response of an impurity in a cylindrical quantum dot under the action of a magnetic field

NASA Astrophysics Data System (ADS)

Portacio, Alfonso A.; Rodríguez, Boris A.; Villamil, Pablo

2017-04-01

The linear and nonlinear optical response in a cylindrical quantum dot (CQD) of GaAs / Ga0.6Al0.4 As with a donor impurity in a uniform magnetic field applied in the axial direction of the cylinder is studied theoretically. The calculations were carried out in approximations of effective mass and two-level quantum systems. Using the variational method, the binding energies and the wave functions of the 1s-like y 2pz-like states for different positions of the impurity inside the CQD were found. It was found that the binding energy is greatest in the center of the CQD and diminishes as the impurity moves radially and/or axially. The optical rectification, the change in the refractive index, and the optical absorption were studied as functions of the energy of a photon incident on the CQD and different intensities of the magnetic field, with an impurity located at various positions. It was found that in a CDQ with an impurity inside, the effect of the variation of the intensity of the magnetic field on the optical response is much less than the effect produced by the variation of the position of the impurity. The physical reason for this behavior is that in nanostructures with impurities the Coulomb confinement is stronger than the magnetic confinement. It was also found that when the impurity is in the center of the quantum dot, the optical rectification coefficient is zero, due to the symmetry that the wave function of the impurity exhibits at this geometric point. When the impurity moves in the axial direction, the symmetry is broken and the optical rectification coefficient is different from zero, and its value increases as the impurity moves away from the center of the CQD.

Impurity-generated non-Abelions

NASA Astrophysics Data System (ADS)

Simion, G.; Kazakov, A.; Rokhinson, L. P.; Wojtowicz, T.; Lyanda-Geller, Y. B.

2018-06-01

Two classes of topological superconductors and Majorana modes in condensed matter systems are known to date: one in which disorder induced by impurities strongly suppresses topological superconducting gap and is detrimental to Majorana modes, and another where Majorana fermions are protected by a disorder-robust topological superconductor gap. Observation and control of Majorana fermions and other non-Abelions often requires a symmetry of an underlying system leading to a gap in the single-particle or quasiparticle spectra. In semiconductor structures, impurities that provide charge carriers introduce states into the gap and enable conductance and proximity-induced superconductivity via the in-gap states. Thus a third class of topological superconductivity and Majorana modes emerges, in which topological superconductivity and Majorana fermions appear exclusively when impurities generate in-gap states. We show that impurity-enabled topological superconductivity is realized in a quantum Hall ferromagnet, when a helical domain wall is coupled to an s -wave superconductor. As an example of emergence of topological superconductivity in quantum Hall ferromagnets, we consider the integer quantum Hall effect in Mn-doped CdTe quantum wells. Recent experiments on transport through the quantum Hall ferromagnet domain wall in this system indicated a vital role of impurities in the conductance, but left unresolved the question whether impurities preclude generation of Majorana fermions and other non-Abelions in such systems in general. Here, solving a general quantum-mechanical problem of impurity bound states in a system of spin-orbit coupled Landau levels, we demonstrate that impurity-induced Majorana modes emerge at boundaries between topological and conventional superconducting states generated in a domain wall due to proximity to an s superconductor. We consider both short-range disorder and a smooth random potential. The phase diagram of the system is defined by characteristic disorder, gate voltage induced angular momentum splitting of impurity levels, and by a proximity superconducting gap. The phase diagram exhibits two ranges of gate voltage with conventional superconducting order separated by a gate voltage range with topological superconductivity. We show that electrostatic control of domain walls in an integer quantum Hall ferromagnet allows manipulation of Majorana fermions. Ferromagnetic transitions in the fractional quantum Hall regime may lead to the formation and electrostatic control of higher order non-Abelian excitations.

Magnetic field effects on the local electronic structure near a single impurity in Graphene

NASA Astrophysics Data System (ADS)

Yang, Ling; Zhu, Jian-Xin; Tsai, Shan-Wen

2011-03-01

Impurities in graphene can have a significant effect on the local electronic structure of graphene when the Fermi level is near the Dirac point. We study the problem of an isolated impurity in a single layer graphene in the presence of a perpendicular magnetic field. We use a linearization approximation for the energy dispersion and employ a T-matrix formalism to calculate the Green's function. We investigate the effect of an external magnetic field on the Friedel oscillations and impurity-induced resonant states. Different types of impurities, such as vacancies, substitutional impurities, and adatoms, are also considered. LY and SWT acknowledge financial support from NSF(DMR-0847801)and from the UC Lab Fees Research Program.

Solidification and Morphological Evolution of Al-Si Eutectics in Convector-Diffusive Conditions

NASA Technical Reports Server (NTRS)

Singh, N. B.; Su, Ching Hua; Arnold, Brad; Choa, Fow-Sen; Mandal, K. D.

2017-01-01

The Al-Si material system is an important and has been studied for over half century with a focus on industrial applications in high strength and high conductivity alloys. A great deal of researches have been focused on controlling the morphology and hence performance through the addition of small impurities and by processing conditions. Most of the structure-property correlations are based on the post solidified micromorphology and growth conditions. This material system is unique and has been explored for heat spreader, controlling coefficient of expansion by adjusting composition of silicon and in designing composites. The Al-Si system is very interesting system for understanding the dendritic (Al-rich side) eutectic transition. Recently this system has been of great interest because of its applications in designing heat spreader, low temperature flux to grow SiC large substrates and in controlling the coefficient of expansion of Al-based alloys. We have performed extensive experiments to understand eutectic transition and to understand the morphological evolution in presence of impurities. We will discuss the results of dendritic transition into faceted long grains in convector-diffusive conditions. In this presentation we will present morphological transition in presence of carbon impurity and development of novel morphology.

Dyakonov-Perel Effect on Spin Dephasing in n-Type GaAs

NASA Technical Reports Server (NTRS)

Ning, C. Z.; Wu, M. W.

2003-01-01

A paper presents a study of the contribution of the Dyakonov-Perel (DP) effect to spin dephasing in electron-donor-doped bulk GaAs in the presence of an applied steady, moderate magnetic field perpendicular to the growth axis of the GaAs crystal. (The DP effect is an electron-wave-vector-dependent spin-state splitting of the conduction band, caused by a spin/orbit interaction in a crystal without an inversion center.) The applicable Bloch equations of kinetics were constructed to include terms accounting for longitudinal optical and acoustic phonon scattering as well as impurity scattering. The contributions of the aforementioned scattering mechanisms to spin-dephasing time in the presence of DP effect were examined by solving the equations numerically. Spin-dephasing time was obtained from the temporal evolution of the incoherently summed spin coherence. Effects of temperature, impurity level, magnetic field, and electron density on spin-dephasing time were investigated. Spin-dephasing time was found to increase with increasing magnetic field. Contrary to predictions of previous simplified treatments of the DP effect, spin-dephasing time was found to increase with temperature in the presence of impurity scattering. These results were found to agree qualitatively with results of recent experiments.

Influence of impurity seeding on the plasma radiation in the EAST tokamak

NASA Astrophysics Data System (ADS)

Liping, DONG; Yanmin, DUAN; Kaiyun, CHEN; Xiuda, YANG; Ling, ZHANG; Feng, XU; Jingbo, CHEN; Songtao, MAO; Zhenwei, WU; Liqun, HU

2018-04-01

Plasma radiation characteristics in EAST argon (Ar) gas and neon (Ne) gas seeding experiments are studied. The radiation profiles reconstructed from the fast bolometer measurement data by tomography method are compared with the ones got from the simulation program based on corona model. And the simulation results coincide roughly with the experimental data. For Ar seeding discharges, the substantial enhanced radiations can be generally observed in the edge areas at normalized radius ρ pol∼0.7–0.9, while the enhanced regions are more outer for Ne seeding discharges. The influence of seeded Ar gas on the core radiation is related to the injected position. In discharges with LSN divertor configuration, the Ar ions can permeate into the core region more easily when being injected from the opposite upper divertor ports. In USN divertor configuration, the W impurity sputtered from the upper divertor target plates are observed to be an important contributor to the increase of the core radiation no matter impurity seeding from any ports. The maximum radiated power fractions f rad (P rad/P heat) about 60%–70% have been achieved in the recent EAST experimental campaign in 2015–2016.

Chaotropic salts in liquid chromatographic method development for the determination of pramipexole and its impurities following quality-by-design principles.

PubMed

Vemić, Ana; Rakić, Tijana; Malenović, Anđelija; Medenica, Mirjana

2015-01-01

The aim of this paper is to present a development of liquid chromatographic method when chaotropic salts are used as mobile phase additives following the QbD principles. The effect of critical process parameters (column chemistry, salt nature and concentration, acetonitrile content and column temperature) on the critical quality attributes (retention of the first and last eluting peak and separation of the critical peak pairs) was studied applying the design of experiments-design space methodology (DoE-DS). D-optimal design is chosen in order to simultaneously examine both categorical and numerical factors in minimal number of experiments. Two ways for the achievement of quality assurance were performed and compared. Namely, the uncertainty originating from the models was assessed by Monte Carlo simulations propagating the error equal to the variance of the model residuals and propagating the error originating from the model coefficients' calculation. The baseline separation of pramipexole and its five impurities is achieved fulfilling all the required criteria while the method validation proved its reliability. Copyright © 2014 Elsevier B.V. All rights reserved.

The judgment of the All-melted-moment during using electron beam melting equipment to purify silicon

NASA Astrophysics Data System (ADS)

Han, Xiaojie; Meng, Jianxiong; Wang, Shuaiye; Jiang, Tonghao; Wang, Feng; Tan, Yi; Jiang, Dachuan

2017-06-01

Experiment has proved that the rate of impurity removal depends on the pressure and the temperature of the vacuum chamber during using electron beam to smelt silicon, and the amount of removed-impurity depends on time when other conditions are the same. In the actual production process, smelting time is a decisive factor of impurity removal amount while pressure and temperature of the vacuum chamber is certain due to a certain melting power. To avoiding the influence of human control and improving the quality of production, thinking of using cooling water temperature to estimate the state of material during metal smelting is considered. We try to use the change of cooling water temperature to judge that when silicon is all melted and to evaluate the effectiveness of this method.

Effect of impurities in polybutene on the quality of alkenylsuccinic anhydrides

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

Yarmolyuk, B.M.; Pustovit, V.E.; Bereza, L.I.

1984-03-01

Synthesis of alkenylsuccini anhydrides (ASAs) was carried out in thermostable ampules at 230/sup 0/C in the course of 12 hours at an MA:PB molar ratio of 1.3:1 in a medium of prepurified petroleum xylene (30%). Freshly distilled maleic anhydride and industrial specimens of polybutene were used in the experiments. It was established that the main impurities which are formed in the production of polybutene and in its processing are ions of sodium, peroxide compounds and products of decomposition of the polymerization catalyst. The concentration of sodium ion was determined by an atomic adsorption method on an A-3000 instrument, the concentrationmore » of peroxides was determined by iodometry (3), and the concentration of catalyst decomposition products was determined from the amount of mechanical impurities.« less

The Effects of Impurities on Protein Crystal Growth and Nucleation: A Preliminary Study

NASA Technical Reports Server (NTRS)

Schall, Constance A.

1998-01-01

Kubota and Mullin (1995) devised a simple model to account for the effects of impurities on crystal growth of small inorganic and organic molecules in aqueous solutions. Experimentally, the relative step velocity and crystal growth of these molecules asymptotically approach zero or non-zero values with increasing concentrations of impurities. Alternatively, the step velocity and crystal growth can linearly approach zero as the impurity concentration increases. The Kubota-Mullin model assumes that the impurity exhibits Langmuirian adsorption onto the crystal surface. Decreases in step velocities and subsequent growth rates are related to the fractional coverage (theta) of the crystal surface by adsorbed impurities; theta = Kx / (I +Kx), x = mole fraction of impurity in solution. In the presence of impurities, the relative step velocity, V/Vo, and the relative growth rate of a crystal face, G/Go, are proposed to conform to the following equations: V/Vo approx. = G/Go = 1 - (alpha)(theta). The adsorption of impurity is assumed to be rapid and in quasi-equilibrium with the crystal surface sites available. When the value of alpha, an effectiveness factor, is one the growth will asymptotically approach zero with increasing concentrations of impurity. At values less than one, growth approaches a non-zero value asymptotically. When alpha is much greater than one, there will be a linear relationship between impurity concentration and growth rates. Kubota and Mullin expect alpha to decrease with increasing supersaturation and shrinking size of a two dimensional nucleus. It is expected that impurity effects on protein crystal growth will exhibit behavior similar to that of impurities in small molecule growth. A number of proteins were added to purified chicken egg white lysozyme, the effect on crystal nucleation and growth assessed.

The influence of impurities on the crystal structure and mechanical properties of additive manufactured U–14at.% Nb

DOE PAGES

Wu, Amanda S.; Brown, Donald W.; Clausen, Bjørn; ...

2017-03-01

Uranium-niobium alloys can exist with significantly different microstructures and mechanical properties, heavily influenced by thermomechanical processing history and impurities. In this study, the influence of Ti and other impurities is studied on uranium-14 at.% niobium additively manufactured using laser powder bed fusion. In two different metallic impurity levels were investigated and a Nb equivalent (Nbeq) composition is defined to represent the impurities. Furthermore, in-situ neutron diffraction during compression loading shows that increased Nbeq promotes the formation of γ°-tetragonal phase at the expense of α''-monoclinic phase, resulting in 2 × higher yield strength than water quenched α'' and a strain inducedmore » transformation to α'' with superelastic strains to 4.5%.« less

An investigation on the effect of impurity position on the binding energy of quantum box under electric field with pressure and temperature

NASA Astrophysics Data System (ADS)

Yilmaz, S.; Kirak, M.

2018-05-01

In the present study, we have studied theoretically the influences of donor impurity position on the binding energy of a GaAs cubic quantum box structure. The binding energy is calculated as functions of the position of impurity, electric field, temperature and hydrostatic pressure. The variational method is employed to obtain the energy eigenvalues of the structure in the framework of the effective mass approximation. It has been found that the impurity positions with electric field, pressure and temperature have an important effect on the binding energy of structure considered. The results can be used to manufacture semiconductor device application by manipulating the binding energy with the impurity positions, electric field, pressure and temperature.

The influence of impurities on the crystal structure and mechanical properties of additive manufactured U–14at.% Nb

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

Wu, Amanda S.; Brown, Donald W.; Clausen, Bjørn

Uranium-niobium alloys can exist with significantly different microstructures and mechanical properties, heavily influenced by thermomechanical processing history and impurities. In this study, the influence of Ti and other impurities is studied on uranium-14 at.% niobium additively manufactured using laser powder bed fusion. In two different metallic impurity levels were investigated and a Nb equivalent (Nbeq) composition is defined to represent the impurities. Furthermore, in-situ neutron diffraction during compression loading shows that increased Nbeq promotes the formation of γ°-tetragonal phase at the expense of α''-monoclinic phase, resulting in 2 × higher yield strength than water quenched α'' and a strain inducedmore » transformation to α'' with superelastic strains to 4.5%.« less

Characterization of the isomeric configuration and impurities of (Z)-endoxifen by 2D NMR, high resolution LC⬜MS, and quantitative HPLC analysis.

PubMed

Elkins, Phyllis; Coleman, Donna; Burgess, Jason; Gardner, Michael; Hines, John; Scott, Brendan; Kroenke, Michelle; Larson, Jami; Lightner, Melissa; Turner, Gregory; White, Jonathan; Liu, Paul

2014-01-01

(Z)-Endoxifen (4-hydroxy-N-desmethyltamoxifen), an active metabolite generated via actions of CYP3A4/5 and CYP2D6, is a more potent selective estrogen receptor modulator (SERM) than tamoxifen. In the MCF-7 human mammary tumor xenograft model with female athymic mice, (Z)-endoxifen, at an oral dose of 4⬜8 mg/kg, significantly inhibits tumor growth. (Z)-Endoxifen's potential as an alternative therapeutic agent independent of CYP2D6 activities, which can vary widely in ER+ breast cancer patients, is being actively evaluated. This paper describes confirmation of the configuration of the active (Z)-isomer through 2D NMR experiments, including NOE (ROESY) to establish spatial proton⬜proton correlations, and identification of the major impurity as the (E)-isomer in endoxifen drug substance by HPLC/HRMS (HPLC/MS-TOF). Stability of NMR solutions was confirmed by HPLC/UV analysis. For pre-clinical studies, a reverse-phase HPLC⬜UV method, with methanol/water mobile phases containing 10 mM ammonium formate at pH 4.3, was developed and validated for the accurate quantitation and impurity profiling of drug substance and drug product. Validation included demonstration of linearity, method precision, accuracy, and specificity in the presence of impurities, excipients (for the drug product), and degradation products. Ruggedness and reproducibility of the method were confirmed by collaborative studies between two independent laboratories. The method is being applied for quality control of the API and oral drug product. Kinetic parameters of Z- to E-isomerization were also delineated in drug substance and in aqueous formulation, showing conversion at temperatures above 25 °C. Copyright © 2014 Elsevier B.V. All rights reserved.

Improvement of a stability-indicating method by Quality-by-Design versus Quality-by-Testing: a case of a learning process.

PubMed

Hubert, C; Lebrun, P; Houari, S; Ziemons, E; Rozet, E; Hubert, Ph

2014-01-01

The understanding of the method is a major concern when developing a stability-indicating method and even more so when dealing with impurity assays from complex matrices. In the presented case study, a Quality-by-Design approach was applied in order to optimize a routinely used method. An analytical issue occurring at the last stage of a long-term stability study involving unexpected impurities perturbing the monitoring of characterized impurities needed to be resolved. A compliant Quality-by-Design (QbD) methodology based on a Design of Experiments (DoE) approach was evaluated within the framework of a Liquid Chromatography (LC) method. This approach allows the investigation of Critical Process Parameters (CPPs), which have an impact on Critical Quality Attributes (CQAs) and, consequently, on LC selectivity. Using polynomial regression response modeling as well as Monte Carlo simulations for error propagation, Design Space (DS) was computed in order to determine robust working conditions for the developed stability-indicating method. This QbD compliant development was conducted in two phases allowing the use of the Design Space knowledge acquired during the first phase to define the experimental domain of the second phase, which constitutes a learning process. The selected working condition was then fully validated using accuracy profiles based on statistical tolerance intervals in order to evaluate the reliability of the results generated by this LC/ESI-MS stability-indicating method. A comparison was made between the traditional Quality-by-Testing (QbT) approach and the QbD strategy, highlighting the benefit of this QbD strategy in the case of an unexpected impurities issue. On this basis, the advantages of a systematic use of the QbD methodology were discussed. Copyright © 2013 Elsevier B.V. All rights reserved.

The Dynamical Mean Field Study of Competition between Ferromagnetism and Disorder in Ferromagnetic Semiconductors

NASA Astrophysics Data System (ADS)

Aryanpour, Karan

2003-03-01

We employ the Dynamical Mean Field Approximation (DMFA) to study the Janko-Zarand model [1] for the combination of large spin-orbit coupling and spatial disorder effects in GaAs doped with Mn. In this model the electronic dispersion and the spin-orbit coupling are simultaneously diagonalized and therefore, the Hamiltonian for the pure system takes a surprisingly simple form. The price for this simplicity is that the quantization axis for the spin must be rotated along the direction of momentum. This chiral basis greatly complicates the form of the hole-impurity interaction at a single site i. In the DMFA, since all the crossing Feynman diagrams for the hole-impurity interaction vanish, the problem simplifies to the local diagrams for the holes scattering off of a single Mn impurity site only. The diagrammatics for the self-energy reduces to the local Green functions and potentials in the non-chiral basis in which they have very simple forms. We first calculate the initial green function G(k) in the chiral basis and then rotate G(k) back into the non chiral basis and coarse grain it over all the k momenta. The hole-impurity interaction is greatly simplified in the non-chiral basis and can be averaged over all the spin configurations and orientations of the Mn atoms on the lattice.The self energy may be extracted from the averaged Green function, and used to recalculate the initial cluster Green function, etc. completing the DMFA self-consistent loop. We intend to calculate the spin and charge transport coefficients, and spectra such as the AC susceptibility and the ARPES which may be directly compared with experiment. [1] Phys. Rev. Lett.89,047201/1-4 (2002)

Power and Particle Exhaust in Tokamaks

ScienceCinema

Dr. Wojciech Fundamenski

2018-04-19

Dr. Fundamenski provides an introduction to plasma exhaust, specifically relating to the EFDA-JET and ITER projects in Europe. Divertor heat loads, impurity seeding, and disruption experiments are outlined.

Coherence Imaging Measurements of Impurity Flow in the CTH and W7-X Experiments

NASA Astrophysics Data System (ADS)

Ennis, D. A.; Allen, N. R.; Hartwell, G. J.; Johnson, C. A.; Maurer, D. A.; Allen, S. L.; Samuell, C. M.; Gradic, D.; Konig, R.; Perseo, V.; W7-X Team

2017-10-01

Measurements of impurity ion emissivity and velocity in the Compact Toroidal Hybrid (CTH) experiment are achieved with a new optical coherence imaging diagnostic. The Coherence Imaging Spectroscopy (CIS) technique uses an imaging interferometer of fixed delay to provide 2D spectral images, making it ideal for investigating the non-axisymmetric geometry of CTH plasmas. Preliminary analysis of C III interferograms indicate a net toroidal flow on the order of 10 km/s during the time of peak current. Bench tests using Zn and Cd light sources reveal that the temperature of the interferometer optics must be controlled to within 0.01°C to limit phase drift resulting in artificially measured flow. A new collaboration between Auburn University and the Max-Planck-Institute for Plasma Physics is underway to develop two new coherence imaging instruments for ion impurity flow measurements in orthogonal directions to investigate the 3D physics of the W7-X island divertor during OP1.2. A continuous wave laser tunable over most of the visible region will be incorporated to provide immediate and accurate calibrations of both CIS systems during plasma operations. Work supported by USDoE Grant DE-FG02-00ER54610.

Effect of a Nitrogen Impurity on the Fundamental Raman Band of Diamond Single Crystals

NASA Astrophysics Data System (ADS)

Gusakov, G. A.; Samtsov, M. P.; Voropay, E. S.

2018-05-01

The effect of nitrogen defects in natural and synthetic diamond single crystals on the position and half-width of the fundamental Raman band was investigated. Samples containing the main types of nitrogen lattice defects at impurity contents of 1-1500 ppm were studied. The parameters of the Stokes and anti-Stokes components in Raman spectra of crystals situated in a cell with distilled water to minimize the influence of heating by the exciting laser radiation were analyzed to determine the effect of a nitrogen impurity in the diamond crystal lattice. It was shown that an increase of impurity atoms in the crystals in the studied concentration range resulted in broadening of the Raman band from 1.61 to 2.85 cm-1 and shifting of the maximum to lower frequency from 1332.65 to 1332.3 cm-1. The observed effect was directly proportional to the impurity concentration and depended on the form of the impurity incorporated into the diamond lattice. It was found that the changes in the position and half-width of the fundamental Raman band for diamond were consistent with the magnitude of crystal lattice distortions due to the presence of impurity defects and obeyed the Gruneisen law.

Spectroscopic characterization and quantitative determination of atorvastatin calcium impurities by novel HPLC method

NASA Astrophysics Data System (ADS)

Gupta, Lokesh Kumar

2012-11-01

Seven process related impurities were identified by LC-MS in the atorvastatin calcium drug substance. These impurities were identified by LC-MS. The structure of impurities was confirmed by modern spectroscopic techniques like 1H NMR and IR and physicochemical studies conducted by using synthesized authentic reference compounds. The synthesized reference samples of the impurity compounds were used for the quantitative HPLC determination. These impurities were detected by newly developed gradient, reverse phase high performance liquid chromatographic (HPLC) method. The system suitability of HPLC analysis established the validity of the separation. The analytical method was validated according to International Conference of Harmonization (ICH) with respect to specificity, precision, accuracy, linearity, robustness and stability of analytical solutions to demonstrate the power of newly developed HPLC method.

Surface Changes and Impurity Release Kinetics of Titanium Dioxide Nanoparticles in Aqueous Environment

EPA Science Inventory

Previous studies have found the significant role of impurities (i.e., silicon, phosphorus) in the aggregation and sedimentation of TiO2 nanoparticles in water environment. However, it is not understood whether dissolution of the impurities potentially impacts the environment or t...

Stability of Weyl metals under imuurity scattering

NASA Astrophysics Data System (ADS)

Huang, Zhoushen; Das, Tanmoy; Balatsky, Alexander V.; Arovas, Daniel P.

2013-03-01

We investigate the effects of bulk impurities on the electronic spectrum of Weyl semimetals, a recently identified class of Dirac-type materials. Using a T-matrix approach, we study resonant scattering due to a localized impurity in tight binding versions of the continuum models recently discussed by Burkov, Hook, and Balents, describing perturbed four-component Dirac fermions in the vicinity of a critical point. The impurity potential is described by a strength g as well as a matrix structure Λ. Unlike the case in d-wave superconductors, where a zero energy resonance can always be induced by varying the impurity scalar and/or magnetic impurity strength, we find that for certain types of impurity (Λ), the Weyl node is protected, and that a scalar impurity will induce an intragap resonance over a wide range of scattering stength. A general framework is developed to address this question, as well as to determine the dependence of resonance energy on the impurity strength. This work is supported in part by the NSF through grant DMR-1007028. Work at LANL was supported by US DoE.

Effects of Impurities in CO2 Spreading Model Development for Field Experiments in the Framework of the CO2QUEST Project

NASA Astrophysics Data System (ADS)

Rebscher, D.; Wolf, J. L.; Jung, B.; Bensabat, J.; Segev, R.; Niemi, A. P.

2014-12-01

The aim of the CO2QUEST project (Impact of the Quality of CO2 on Storage and Transport) is to investigate the effect of typical impurities in the CO2 stream captured from fossil fuel power plants on its safe and economic transportation and deep geologic storage. An important part of this EU funded project is to enhance the understanding of typical impurity effects in a CO2 stream regarding the performance of the storage. Based on the experimental site Heletz in Israel, where injection tests of water as well as of super-critical pure and impure CO2 will be conducted, numerical simulations are performed. These studies illustrate flow and transport of CO2 and brine as well as impurities induced chemical reactions in relation to changes in the reservoir, e.g. porosity, permeability, pH-value, and mineral composition. Using different THC codes (TOUGH2-ECO2N, TOUGHREACT, PFLOTRAN), the spatial distribution of CO2 and impurities, both in the supercritical and aqueous phases, are calculated. The equation of state (EOS) of above numerical codes are properly modified to deal with binary/tertiary gas mixtures (e.g. CO2-N2 or CO2-SO2). In addition, simulations for a push-pull test of about 10 days duration are performed, which will be validated against experimental field data. Preliminary results are as follows: (a) As expected, the injection of SO2 leads to a strong decrease in pH-value, hence, the total dissolution of carbonate minerals could be observed. (b) Due to the acidic attack on clay minerals , which is enhanced compared to a pure CO2 dissolution, a higher amount of metal ions are released, in particular Fe2+ and Mg2+ by a factor of 25 and 10, respectively. Whereas secondary precipitation occurs only for sulphur minerals, namely anhydrite and pyrite. (c) The co-injection of CO2 with N2 changes physical properties of the gas mixture. Increasing N2 contents induces density decrease of the gas mixture, resulting in faster and wider plume migration compared to the pure CO2 injection case.

Development of visual peak selection system based on multi-ISs normalization algorithm to apply to methamphetamine impurity profiling.

PubMed

Lee, Hun Joo; Han, Eunyoung; Lee, Jaesin; Chung, Heesun; Min, Sung-Gi

2016-11-01

The aim of this study is to improve resolution of impurity peaks using a newly devised normalization algorithm for multi-internal standards (ISs) and to describe a visual peak selection system (VPSS) for efficient support of impurity profiling. Drug trafficking routes, location of manufacture, or synthetic route can be identified from impurities in seized drugs. In the analysis of impurities, different chromatogram profiles are obtained from gas chromatography and used to examine similarities between drug samples. The data processing method using relative retention time (RRT) calculated by a single internal standard is not preferred when many internal standards are used and many chromatographic peaks present because of the risk of overlapping between peaks and difficulty in classifying impurities. In this study, impurities in methamphetamine (MA) were extracted by liquid-liquid extraction (LLE) method using ethylacetate containing 4 internal standards and analyzed by gas chromatography-flame ionization detection (GC-FID). The newly developed VPSS consists of an input module, a conversion module, and a detection module. The input module imports chromatograms collected from GC and performs preprocessing, which is converted with a normalization algorithm in the conversion module, and finally the detection module detects the impurities in MA samples using a visualized zoning user interface. The normalization algorithm in the conversion module was used to convert the raw data from GC-FID. The VPSS with the built-in normalization algorithm can effectively detect different impurities in samples even in complex matrices and has high resolution keeping the time sequence of chromatographic peaks the same as that of the RRT method. The system can widen a full range of chromatograms so that the peaks of impurities were better aligned for easy separation and classification. The resolution, accuracy, and speed of impurity profiling showed remarkable improvement. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Liquid xenon purification, de-radonation (and de-kryptonation)

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

Pocar, Andrea, E-mail: pocar@umass.edu; Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94550

Liquid xenon detectors are at the forefront of rare event physics, including searches for neutrino-less double beta decay and WIMP dark matter. The xenon for these experiments needs to be purified from chemical impurities such as electronegative atoms and molecules, which absorb ionization electrons, and VUV (178 nm) scintillation light-absorbing chemical species. In addition, superb purification from radioactive impurities is required. Particularly challenging are radioactive noble isotopes ({sup 85}Kr,{sup 39,42}Ar,{sup 220,222}Rn). Radon is a particularly universal problem, due to the extended decay sequence of its daughters and its ubiquitous presence in detector materials. Purification and de-radonation of liquid xenon aremore » addressed with particular focus on the experience gained with the EXO-200 neutrino-less double beta decay detector.« less

The synthesis and characterisation of MDMA derived from a catalytic oxidation of material isolated from black pepper reveals potential route specific impurities.

PubMed

Plummer, Christopher M; Breadon, Thomas W; Pearson, James R; Jones, Oliver A H

2016-05-01

This work examines the chemical synthesis of 3,4-methylenedioxy-N-methylamphetamine (MDMA) from piperonal prepared via a catalytic ruthenium tetroxide oxidation of piperine extracted from black pepper. A variety of oxidation conditions were experimented with including different solvent systems and co-oxidants. A sample of prepared piperonal was successfully converted into MDMA via 3,4-methylenedioxyphenyl-2-nitropropene (MDP2NP) and 3,4-methylenedioxyphenyl-2-propanone (MDP2P) and the impurities within each product characterised by GC-MS to give a contaminant profile of the synthetic pathway. Interestingly, it was discovered that a chlorinated analogue of piperonal (6-chloropiperonal) was created during the oxidation process by an as yet unknown mechanism. This impurity reacted alongside piperonal to give chlorinated analogues of each precursor, ultimately yielding 2-chloro-4,5-methylenedioxymethamphetamine (6-Cl-MDMA) as an impurity within the MDMA sample. The methodology developed is a simple way to synthesise a substantial amount of precursor material with easy to obtain reagents. The results also show that chlorinated MDMA analogues, previously thought to be deliberately included adulterants, may in fact be route specific impurities with potential application in determining the origin and synthesis method of seized illicit drugs. Copyright © 2016 The Chartered Society of Forensic Sciences. Published by Elsevier Ireland Ltd. All rights reserved.

Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique: I. Impact of Impurities, Measurement Protocols and Applied Corrections

DOE PAGES

Shinozaki, Kazuma; Zack, Jason W.; Richards, Ryan M.; ...

2015-07-22

The rotating disk electrode (RDE) technique is being extensively used as a screening tool to estimate the activity of novel PEMFC electrocatalysts synthesized in lab-scale (mg) quantities. Discrepancies in measured activity attributable to glassware and electrolyte impurity levels, as well as conditioning, protocols and corrections are prevalent in the literature. Moreover, the electrochemical response to a broad spectrum of commercially sourced perchloric acid and the effect of acid molarity on impurity levels and solution resistance were also assessed. Our findings reveal that an area specific activity (SA) exceeding 2.0 mA/cm 2 (20 mV/s, 25°C, 100 kPa, 0.1 M HClO 4)more » for polished poly-Pt is an indicator of impurity levels that do not impede the accurate measurement of the ORR activity of Pt based catalysts. After exploring various conditioning protocols to approach maximum utilization of the electrochemical area (ECA) and peak ORR activity without introducing catalyst degradation, an investigation of measurement protocols for ECA and ORR activity was conducted. Down-selected protocols were based on the criteria of reproducibility, duration of experiments, impurity effects and magnitude of pseudo-capacitive background correction. In sum, statistical reproducibility of ORR activity for poly-Pt and Pt supported on high surface area carbon was demonstrated.« less

Thermoelectric current in topological insulator nanowires with impurities.

PubMed

Erlingsson, Sigurdur I; Bardarson, Jens H; Manolescu, Andrei

2018-01-01

In this paper we consider charge current generated by maintaining a temperature difference over a nanowire at zero voltage bias. For topological insulator nanowires in a perpendicular magnetic field the current can change sign as the temperature of one end is increased. Here we study how this thermoelectric current sign reversal depends on the magnetic field and how impurities affect the size of the thermoelectric current. We consider both scalar and magnetic impurities and show that their influence on the current are quite similar, although the magnetic impurities seem to be more effective in reducing the effect. For moderate impurity concentration the sign reversal persists.

Luminescent Processes Elucidated by Simple Experiments on ZnS.

ERIC Educational Resources Information Center

Schwankner, R.; And Others

1981-01-01

Describes some impurity-related optical properties of semiconductors, with special emphasis on the luminescence of zinc sulfide (ZnS). Presents and interprets five experiments using a ZnS screen, ultraviolet lamp, transparent Dewar liquid nitrogen, and a helium/neon gas base. Includes application of luminescence measurements to archaeology. (SK)

Silicon as a model ion trap: Time domain measurements of donor Rydberg states

PubMed Central

Vinh, N. Q.; Greenland, P. T.; Litvinenko, K.; Redlich, B.; van der Meer, A. F. G.; Lynch, S. A.; Warner, M.; Stoneham, A. M.; Aeppli, G.; Paul, D. J.; Pidgeon, C. R.; Murdin, B. N.

2008-01-01

One of the great successes of quantum physics is the description of the long-lived Rydberg states of atoms and ions. The Bohr model is equally applicable to donor impurity atoms in semiconductor physics, where the conduction band corresponds to the vacuum, and the loosely bound electron orbiting a singly charged core has a hydrogen-like spectrum according to the usual Bohr–Sommerfeld formula, shifted to the far-infrared because of the small effective mass and high dielectric constant. Manipulation of Rydberg states in free atoms and ions by single and multiphoton processes has been tremendously productive since the development of pulsed visible laser spectroscopy. The analogous manipulations have not been conducted for donor impurities in silicon. Here, we use the FELIX pulsed free electron laser to perform time-domain measurements of the Rydberg state dynamics in phosphorus- and arsenic-doped silicon and we have obtained lifetimes consistent with frequency domain linewidths for isotopically purified silicon. This implies that the dominant decoherence mechanism for excited Rydberg states is lifetime broadening, just as for atoms in ion traps. The experiments are important because they represent a step toward coherent control and manipulation of atomic-like quantum levels in the most common semiconductor and complement magnetic resonance experiments in the literature, which show extraordinarily long spin lattice relaxation times—key to many well known schemes for quantum computing qubits—for the same impurities. Our results, taken together with the magnetic resonance data and progress in precise placement of single impurities, suggest that doped silicon, the basis for modern microelectronics, is also a model ion trap.

Structural elucidation of potential impurities in Azilsartan bulk drug by HPLC.

PubMed

Zhou, Wentao; Zhou, Yuxia; Sun, Lili; Zou, Qiaogen; Wei, Ping; Ouyang, Pingkai

2014-01-01

During the synthesis of Azilsartan (AZS), it was speculated that 15 potential impurities would arise. This study investigated the possible mechanism for the formation of 14 of them, and their structures were characterized and confirmed by IR, NMR, and MS techniques. In addition, an efficient chromatographic method was developed to separate and quantify these impurities, using an Inertsil ODS-3 column (250 x 4.6 mm, 5 pm) in gradient mode with a mixture of acetonitrile and the potassium dihydrogen orthophosphate buffer (10 mM, pH adjusted to 3.0 with phosphoric acid). The HPLC method was validated for specificity, precision, accuracy, and sensitivity. LOQ of impurities were in the range of 1.04-2.20 ng. Correlation coefficient values of linearity were >0.9996 for AZS and its impurities. The mean recoveries of all impurities in AZS were between 93.0 and 109.7%. Thus, the validated HPLC method is suitable for the separation and quantification of all potential impurities in AZS.

Low-temperature charged impurity scattering-limited conductivity in relatively high doped bilayer graphene

NASA Astrophysics Data System (ADS)

Hu, Bo

2015-08-01

Based on semiclassical Boltzamnn transport theory in random phase approximation, we develop a theoretical model to investigate low-temperature carrier transport properties in relatively high doped bilayer graphene. In the presence of both electron-hole puddles and band gap induced by charged impurities, we calculate low-temperature charged impurity scattering-limited conductivity in relatively high doped bilayer graphene. Our calculated conductivity results are in excellent agreement with published experimental data in all compensated gate voltage regime of study by using potential fluctuation parameter as only one free fitting parameter, indicating that both electron-hole puddles and band gap induced by charged impurities play an important role in carrier transport. More importantly, we also find that the conductivity not only depends strongly on the total charged impurity density, but also on the top layer charged impurity density, which is different from that obtained by neglecting the opening of band gap, especially for bilayer graphene with high top layer charged impurity density.

Impurity in a Bose-Einstein condensate: Study of the attractive and repulsive branch using quantum Monte Carlo methods

NASA Astrophysics Data System (ADS)

Ardila, L. A. Peña; Giorgini, S.

2015-09-01

We investigate the properties of an impurity immersed in a dilute Bose gas at zero temperature using quantum Monte Carlo methods. The interactions between bosons are modeled by a hard-sphere potential with scattering length a , whereas the interactions between the impurity and the bosons are modeled by a short-range, square-well potential where both the sign and the strength of the scattering length b can be varied by adjusting the well depth. We characterize the attractive and the repulsive polaron branch by calculating the binding energy and the effective mass of the impurity. Furthermore, we investigate the structural properties of the bath, such as the impurity-boson contact parameter and the change of the density profile around the impurity. At the unitary limit of the impurity-boson interaction, we find that the effective mass of the impurity remains smaller than twice its bare mass, while the binding energy scales with ℏ2n2 /3/m , where n is the density of the bath and m is the common mass of the impurity and the bosons in the bath. The implications for the phase diagram of binary Bose-Bose mixtures at low concentrations are also discussed.

Kinetic theory for a mobile impurity in a degenerate Tonks-Girardeau gas.

PubMed

Gamayun, O; Lychkovskiy, O; Cheianov, V

2014-09-01

A kinetic theory describing the motion of an impurity particle in a degenerate Tonks-Girardeau gas is presented. The theory is based on the one-dimensional Boltzmann equation. An iterative procedure for solving this equation is proposed, leading to the exact solution in a number of special cases and to an approximate solution with the explicitly specified precision in a general case. Previously we reported that the impurity reaches a nonthermal steady state, characterized by an impurity momentum p(∞) depending on its initial momentum p(0) [E. Burovski, V. Cheianov, O. Gamayun, and O. Lychkovskiy, Phys. Rev. A 89, 041601(R) (2014)]. In the present paper the detailed derivation of p(∞)(p(0)) is provided. We also study the motion of an impurity under the action of a constant force F. It is demonstrated that if the impurity is heavier than the host particles, m(i)>m(h), damped oscillations of the impurity momentum develop, while in the opposite case, m(i)

Low cost silicon solar array project silicon materials task: Establishment of the feasibility of a process capable of low-cost, high volume production of silane (step 1) and the pyrolysis of silane to semiconductor-grade silicon (step 2)

NASA Technical Reports Server (NTRS)

Breneman, W. C.; Cheung, H.; Farrier, E. G.; Morihara, H.

1977-01-01

A quartz fluid bed reactor capable of operating at temperatures of up to 1000 C was designed, constructed, and successfully operated. During a 30 minute experiment, silane was decomposed within the reactor with no pyrolysis occurring on the reactor wall or on the gas injection system. A hammer mill/roller-crusher system appeared to be the most practical method for producing seed material from bulk silicon. No measurable impurities were detected in the silicon powder produced by the free space reactor, using the cathode layer emission spectroscopic technique. Impurity concentration followed by emission spectroscopic examination of the residue indicated a total impurity level of 2 micrograms/gram. A pellet cast from this powder had an electrical resistivity of 35 to 45 ohm-cm and P-type conductivity.

Nonequilibrium theory of tunneling into a localized state in a superconductor

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

Martin, Ivar; Mozyrsky, Dmitry

2014-09-01

A single static magnetic impurity in a fully gapped superconductor leads to the formation of an intragap quasiparticle bound state. At temperatures much below the superconducting transition, the energy relaxation and spin dephasing of the state are expected to be exponentially suppressed. The presence of such a state can be detected in electron tunneling experiments as a pair of conductance peaks at positive and negative biases. Here we show that, for an arbitrarily weak tunneling strength, the peaks have to be symmetric with respect to the applied bias. This is in contrast to the standard result in which the tunnelingmore » conductance is proportional to the local (in general, particle-hole asymmetric) density of states. The asymmetry can be recovered if one allows for either a finite density of impurity states, or if impurities are coupled to another, nonsuperconducting, equilibrium bath.« less

Large enhancement of the spin Hall effect in Au by side-jump scattering on Ta impurities

NASA Astrophysics Data System (ADS)

Laczkowski, P.; Fu, Y.; Yang, H.; Rojas-Sánchez, J.-C.; Noel, P.; Pham, V. T.; Zahnd, G.; Deranlot, C.; Collin, S.; Bouard, C.; Warin, P.; Maurel, V.; Chshiev, M.; Marty, A.; Attané, J.-P.; Fert, A.; Jaffrès, H.; Vila, L.; George, J.-M.

2017-10-01

We present measurements of the spin Hall effect (SHE) in AuW and AuTa alloys for a large range of W or Ta concentrations by combining experiments on lateral spin valves and ferromagnetic-resonance/spin-pumping techniques. The main result is the identification of a large enhancement of the spin Hall angle (SHA) by the side-jump mechanism on Ta impurities, with a SHA as high as +0.5 (i.e., 50 % ) for about 10% of Ta. In contrast, the SHA in AuW does not exceed +0.15 and can be explained by intrinsic SHE of the alloy without significant extrinsic contribution from skew or side-jump scattering by W impurities. The AuTa alloys, as they combine a very large SHA with a moderate resistivity (smaller than 85 μ Ω cm ), are promising for spintronic devices exploiting the SHE.

Harmful situations, impure people: an attribution asymmetry across moral domains.

PubMed

Chakroff, Alek; Young, Liane

2015-03-01

People make inferences about the actions of others, assessing whether an act is best explained by person-based versus situation-based accounts. Here we examine people's explanations for norm violations in different domains: harmful acts (e.g., assault) and impure acts (e.g., incest). Across four studies, we find evidence for an attribution asymmetry: people endorse more person-based attributions for impure versus harmful acts. This attribution asymmetry is partly explained by the abnormality of impure versus harmful acts, but not by differences in the moral wrongness or the statistical frequency of these acts. Finally, this asymmetry persists even when the situational factors that lead an agent to act impurely are stipulated. These results suggest that, relative to harmful acts, impure acts are linked to person-based attributions. Copyright © 2014 Elsevier B.V. All rights reserved.

Impact of iron-site defects on superconductivity in LiFeAs

DOE PAGES

Chi, Shun; Aluru, Ramakrishna; Singh, Udai Raj; ...

2016-10-19

In conventional s -wave superconductors, only magnetic impurities exhibit impurity bound states, whereas for an s ± order parameter they can occur for both magnetic and nonmagnetic impurities. Impurity bound states in superconductors can thus provide important insight into the order parameter. We present a combined experimental and theoretical study of native and engineered iron-site defects in LiFeAs. A detailed comparison of tunneling spectra measured on impurities with spin-fluctuation theory reveals a continuous evolution from negligible impurity-bound-state features for weaker scattering potential to clearly detectable states for somewhat stronger scattering potentials. Furthermore, all bound states for these intermediate strengthmore » potentials are pinned at or close to the gap edge of the smaller gap, a phenomenon that we explain and ascribe to multiorbital physics.« less

Effects of low-Z and high-Z impurities on divertor detachment and plasma confinement

DOE PAGES

Wang, H. Q.; Guo, Houyang Y.; Petrie, Thomas W.; ...

2017-03-18

The impurity-seeded detached divertor is essential for heat exhaust in ITER and other reactor-relevant devices. Dedicated experiments with injection of N 2, Ne and Ar have been performed in DIII-D to assess the impact of the different impurities on divertor detachment and confinement. Seeding with N 2, Ne and Ar all promote divertor detachment, greatly reducing heat flux near the strike point. The upstream plasma density at the onset of detachment decreases with increasing impurity-puffing flow rates. For all injected impurity species, the confinement and pedestal pressure are correlated with the impurity content and the ratio of separatrix loss powermore » to the L-H transition threshold power. As the divertor plasma approaches detachment, the high-Z impurity seeding tends to degrade the core confinement owing to the increased core radiation. In particular, Ar injection leads to an increase in core radiation, up to 50% of the injected power, and a reduction in pedestal temperature over 60%, thus significantly degrading the confinement, i.e., with H 98 reducing from 1.1 to below 0.7. As for Ne seeding, H 98 near 0.8 can be maintained during the detachment phase with the pedestal temperature being reduced by about 50%. In contrast, in the N 2 seeded plasmas, radiation is predominately confined in the boundary plasma, with up to 50% of heating power being radiated in the divertor region and less than 25% in the core at the onset of detachment. In the case of strong N 2 gas puffing, the confinement recovers during the detachment, from ~20% reduction at the onset of the detachment to greater than that before the seeding. The core and pedestal temperatures feature a reduction of 30% from the initial attached phase and remain nearly constant during the detachment phase. The improvement in confinement appears to arise from the increase in pedestal and core density despite the temperature reduction.« less

Protein Crystallization

NASA Technical Reports Server (NTRS)

Chernov, Alexander A.

2005-01-01

Nucleation, growth and perfection of protein crystals will be overviewed along with crystal mechanical properties. The knowledge is based on experiments using optical and force crystals behave similar to inorganic crystals, though with a difference in orders of magnitude in growing parameters. For example, the low incorporation rate of large biomolecules requires up to 100 times larger supersaturation to grow protein, rather than inorganic crystals. Nucleation is often poorly reproducible, partly because of turbulence accompanying the mixing of precipitant with protein solution. Light scattering reveals fluctuations of molecular cluster size, its growth, surface energies and increased clustering as protein ages. Growth most often occurs layer-by-layer resulting in faceted crystals. New molecular layer on crystal face is terminated by a step where molecular incorporation occurs. Quantitative data on the incorporation rate will be discussed. Rounded crystals with molecularly disordered interfaces will be explained. Defects in crystals compromise the x-ray diffraction resolution crucially needed to find the 3D atomic structure of biomolecules. The defects are immobile so that birth defects stay forever. All lattice defects known for inorganics are revealed in protein crystals. Contribution of molecular conformations to lattice disorder is important, but not studied. This contribution may be enhanced by stress field from other defects. Homologous impurities (e.g., dimers, acetylated molecules) are trapped more willingly by a growing crystal than foreign protein impurities. The trapped impurities induce internal stress eliminated in crystals exceeding a critical size (part of mni for ferritin, lysozyme). Lesser impurities are trapped from stagnant, as compared to the flowing, solution. Freezing may induce much more defects unless quickly amorphysizing intracrystalline water.

Erosion and Retention Properties of Beyllium

NASA Astrophysics Data System (ADS)

Doerner, R.; Grossman, A.; Luckhardt, S.; Serayderian, R.; Sze, F. C.; Whyte, D. G.

1997-11-01

Experiments in PISCES-B have investigated the erosion and hydrogen retention characteristics of beryllium. The sputtering yield is strongly influenced by trace amounts (≈1 percent) of intrinsic plasma impurities. At low sample exposure temperatures (below 250^oC), the beryllium surface remains free of contaminants and a sputtering yield similar to that of beryllium-oxide is measured. At higher exposure temperatures, impurities deposited on the surface can diffuse into the bulk and reduce their chance of subsequent erosion. These impurities form a surface layer mixed with beryllium which exhibits a reduced sputtering yield. Depth profile analysis has determined the composition and chemical bonding of the impurity layer. The hydrogen isotope retention of beryllium under ITER first wall (temperature = 200^oC, ion flux = 1 x 10^21 m-2 s-1) and baffle (temperature = 500^oC, ion flux = 1 x 10^22 m-2 s-1) conditions has been investigated. The retained deuterium saturates above a fluence of 10^23 m-2 at about 4 x 10^20 m-2 for the 200^oC exposure and at 2 x 10^20 m-2 for the 500^oC case. The TMAP code is used to model the deuterium release characteristics.

Metal impurity-assisted formation of nanocone arrays on Si by low energy ion-beam irradiation

NASA Astrophysics Data System (ADS)

Steeves Lloyd, Kayla; Bolotin, Igor L.; Schmeling, Martina; Hanley, Luke; Veryovkin, Igor V.

2016-10-01

Fabrication of nanocone arrays on Si surfaces was demonstrated using grazing incidence irradiation with 1 keV Ar+ ions concurrently sputtering the surface and depositing metal impurity atoms on it. Among three materials compared as co-sputtering targets Si, Cu and stainless steel, only steel was found to assist the growth of dense arrays of nanocones at ion fluences between 1018 and 1019 ions/cm2. The structural characterization of samples irradiated with these ion fluences using Scanning Electron Microscopy and Atomic Force Microscopy revealed that regions far away from co-sputtering targets are covered with nanoripples, and that nanocones popped-up out of the rippled surfaces when moving closer to co-sputtering targets, with their density gradually increasing and reaching saturation in the regions close to these targets. The characterization of the samples' chemical composition with Total Reflection X-ray Fluorescence Spectrometry and X-ray Photoelectron Spectroscopy revealed that the concentration of metal impurities originating from stainless steel (Fe, Cr and Ni) was relatively high in the regions with high density of nanocones (Fe reaching a few atomic percent) and much lower (factor of 10 or so) in the region of nanoripples. Total Reflection X-ray Fluorescence Spectrometry measurements showed that higher concentrations of these impurities are accumulated under the surface in both regions. X-ray Photoelectron Spectroscopy experiments showed no direct evidence of metal silicide formation occurring on one region only (nanocones or nanoripples) and thus showed that this process could not be the driver of nanocone array formation. Also, these measurements indicated enhancement in oxide formation on regions covered by nanocones. Overall, the results of this study suggest that the difference in concentration of metal impurities in the thin near-surface layer forming under ion irradiation might be responsible for the differences in surface structures.

Calculation of the spin-polarized electronic structure of an interstitial iron impurity in silicon

NASA Astrophysics Data System (ADS)

Katayama-Yoshida, H.; Zunger, Alex

1985-06-01

We apply our self-consistent, all-electron, spin-polarized Green's-function method within an impurity-centered, dynamic basis set to study the interstitial iron impurity in silicon. We use two different formulations of the interelectron interactions: the local-spin-density (LSD) formalism and the self-interaction-corrected (SIC) local-spin-density (SIC-LSD) formalism. We find that the SIC-LSD approach is needed to obtain the correct high-spin ground state of Si:Fe+. We propose a quantitative explanation to the observed donor ionization energy and the high-spin ground states for Si:Fe+ within the SIC-LSD approach. For both Si:Fe0 and Si:Fe+, this approach leads to a hyperfine field, contact spin density, and ionization energy in better agreement with experiments than the simple LSD approach. The apparent dichotomy between the covalently delocalized nature of Si:Fe as suggested on the one hand by its reduced hyperfine field (relative to the free atom) and extended spin density and by the occurrence of two closely spaced, stable charge states (within 0.4 eV) and on the other hand by the atomically localized picture (suggested, for example, by the stability of a high-spin, ground-state configuration) is resolved. We find a large reduction in the hyperfine field and contact spin density due to the covalent hybridization between the impurity 3d orbitals and the tails of the delocalized sp3 hybrid orbitals of the surrounding silicon atoms. Using the calculated results, we discuss (i) the underlying mechanism for the stability and plurality of charged states, (ii) the covalent reduction in the hyperfine field, (iii) the remarkable constancy of the impurity Mössbauer isomer shift for different charged states, (iv) comparison with the multiple charged states in ionic crystals, and (v) some related speculation about the mechanism of (Fe2+/Fe3+) oxidation-reduction ionizations in heme proteins and electron-transporting biological systems.

Photon-induced electro-chemical processes in airless icy bodies analogues

NASA Astrophysics Data System (ADS)

Marchione, Demian; Gudipati, Murthy

2016-10-01

Previous laboratory studies have shown that radiation-induced ionization of impurities in water-rich ices drives the formation of ionized species resulting in charge generation and accumulation in ices [1-3]. It is expected that some of these impurity ions are decomposed into smaller volatile species and ejected into the vacuum. These processes are relevant to the chemical composition of the near-surface tenuous (thin) atmosphere of icy bodies such as the Jovian satellites like Europa.Our work aims at investigating photocurrents from organic impurity embedded water ices of several microns thick and understanding how these measurements correlate with the desorption of volatiles during UV and electron irradiation. These experiments are performed in an ultrahigh vacuum chamber around Europa's surface temperature (100 - 150 K) conditions using a low-pressure hydrogen flow-discharge lamp emitting primarily at Lyα (121.6 nm), a 2 keV electron source, and a substrate-less electrode. Photoionization of organic impurities in the water matrix results in charge pair (electron and ion) separation within the ice, and hence in detectable currents that are measured as a function of the applied bias and the temperature (5 K - 200 K). Photodesorption products are also identified by a quadrupole mass spectrometer (QMS) and correlated with conductivity measurements. We will discuss these results in the context of expected Europa's surface photoconductivity and near-surface volatile production.References:[1] M. S. Gudipati, and L. J. Allamandola, Astrophysical Journal Letters, 2003, 596(2), L195-L198.[2] M. S. Gudipati, Journal of Physical Chemistry A, 2004, 108(20), 4412-4419.[3] S. H. Cuylle, L. J. Allamandola, and H. Linnartz, Astronomy and Astrophysics, 2014, 562, A22.This work has been carried out at Jet Propulsion Laboratory, California Institute of Technology under a contract with the National Aeronautics and Space Administration, and funded by NASA under Planetary Atmospheres Program Grant "Understanding the Near-Surface Atmospheres of Icy Bodies: Role of Photoionization of Organic Impurities in Icy Surfaces"

HB-LINE ANION EXCHANGE PURIFICATION OF AFS-2 PLUTONIUM FOR MOX

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

Kyser, E. A.; King, W. D.

2012-07-31

Non-radioactive cerium (Ce) and radioactive plutonium (Pu) anion exchange column experiments using scaled HB-Line designs were performed to investigate the feasibility of using either gadolinium nitrate (Gd) or boric acid (B as H{sub 3}BO{sub 3}) as a neutron poison in the H-Canyon dissolution process. Expected typical concentrations of probable impurities were tested and the removal of these impurities by a decontamination wash was measured. Impurity concentrations are compared to two specifications - designated as Column A or Column B (most restrictive) - proposed for plutonium oxide (PuO{sub 2}) product shipped to the Mixed Oxide (MOX) Fuel Fabrication Facility (MFFF). Usemore » of Gd as a neutron poison requires a larger volume of wash for the proposed Column A specification. Since boron (B) has a higher proposed specification and is more easily removed by washing, it appears to be the better candidate for use in the H-Canyon dissolution process. Some difficulty was observed in achieving the Column A specification due to the limited effectiveness that the wash step has in removing the residual B after ~4 BV's wash. However a combination of the experimental 10 BV's wash results and a calculated DF from the oxalate precipitation process yields an overall DF sufficient to meet the Column A specification. For those impurities (other than B) not removed by 10 BV's of wash, the impurity is either not expected to be present in the feedstock or process, or recommendations have been provided for improvement in the analytical detection/method or validation of calculated results. In summary, boron is recommended as the appropriate neutron poison for H-Canyon dissolution and impurities are expected to meet the Column A specification limits for oxide production in HB-Line.« less

HB-LINE ANION EXCHANGE PURIFICATION OF AFS-2 PLUTONIUM FOR MOX

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

Kyser, E.; King, W.

2012-04-25

Non-radioactive cerium (Ce) and radioactive plutonium (Pu) anion exchange column experiments using scaled HB-Line designs were performed to investigate the feasibility of using either gadolinium nitrate (Gd) or boric acid (B as H{sub 3}BO{sub 3}) as a neutron poison in the H-Canyon dissolution process. Expected typical concentrations of probable impurities were tested and the removal of these impurities by a decontamination wash was measured. Impurity concentrations are compared to two specifications - designated as Column A or Column B (most restrictive) - proposed for plutonium oxide (PuO{sub 2}) product shipped to the Mixed Oxide (MOX) Fuel Fabrication Facility (MFFF). Usemore » of Gd as a neutron poison requires a larger volume of wash for the proposed Column A specification. Since boron (B) has a higher proposed specification and is more easily removed by washing, it appears to be the better candidate for use in the H-Canyon dissolution process. Some difficulty was observed in achieving the Column A specification due to the limited effectiveness that the wash step has in removing the residual B after {approx}4 BV's wash. However a combination of the experimental 10 BV's wash results and a calculated DF from the oxalate precipitation process yields an overall DF sufficient to meet the Column A specification. For those impurities (other than B) not removed by 10 BV's of wash, the impurity is either not expected to be present in the feedstock or process, or recommendations have been provided for improvement in the analytical detection/method or validation of calculated results. In summary, boron is recommended as the appropriate neutron poison for H-Canyon dissolution and impurities are expected to meet the Column A specification limits for oxide production in HB-Line.« less

A novel stability-indicating UPLC method development and validation for the determination of seven impurities in various diclofenac pharmaceutical dosage forms.

PubMed

Azougagh, M; Elkarbane, M; Bakhous, K; Issmaili, S; Skalli, A; Iben Moussad, S; Benaji, B

2016-09-01

An innovative simple, fast, precise and accurate ultra-high performance liquid chromatography (UPLC) method was developed for the determination of diclofenac (Dic) along with its impurities including the new dimer impurity in various pharmaceutical dosage forms. An Acquity HSS T3 (C18, 100×2.1mm, 1.8μm) column in gradient mode was used with mobile phase comprising of phosphoric acid, which has a pH value of 2.3 and methanol. The flow rate and the injection volume were set at 0.35ml·min(-1) and 1μl, respectively, and the UV detection was carried out at 254nm by using photodiode array detector. Dic was subjected to stress conditions from acid, base, hydrolytic, thermal, oxidative and photolytic degradation. The new developed method was successfully validated in accordance to the International Conference on Harmonization (ICH) guidelines with respect to specificity, limit of detection, limit of quantitation, precision, linearity, accuracy and robustness. The degradation products were well resolved from main peak and its seven impurities, proving the specificity power of the method. The method showed good linearity with consistent recoveries for Dic content and its impurities. The relative percentage of standard deviation obtained for the repeatability and intermediate precision experiments was less than 3% and LOQ was less than 0.5μg·ml(-1) for all compounds. The new proposed method was found to be accurate, precise, specific, linear and robust. In addition, the method was successfully applied for the assay determination of Dic and its impurities in the several pharmaceutical dosage forms. Copyright © 2016 Académie Nationale de Pharmacie. Published by Elsevier Masson SAS. All rights reserved.

Analysis of electron temperature, impurity transport and MHD activity with multi-energy soft x-ray diagnostic in EAST tokamak

NASA Astrophysics Data System (ADS)

Heng, LAN; Guosheng, XU; Kevin, TRITZ; Ning, YAN; Tonghui, SHI; Yongliang, LI; Tengfei, WANG; Liang, WANG; Jingbo, CHEN; Yanmin, DUAN; Yi, YUAN; Youwen, SUN; Shuai, GU; Qing, ZANG; Ran, CHEN; Liang, CHEN; Xingwei, ZHENG; Shuliang, CHEN; Huan, LIU; Yang, YE; Huiqian, WANG; Baonian, WAN; the EAST Team

2017-12-01

A new edge tangential multi-energy soft x-ray (ME-SXR) diagnostic with high temporal (≤ 0.1 ms) and spatial (∼1 cm) resolution has been developed for a variety of physics topics studies in the EAST tokamak plasma. The fast edge electron temperature profile (approximately from r/a∼ 0.6 to the scrape-off layer) is investigated using ME-SXR diagnostic system. The data process was performed by the ideal ‘multi-foil’ technique, with no priori assumptions of plasma profiles. Reconstructed ME-SXR emissivity profiles for a variety of EAST experimental scenarios are presented here for the first time. The applications of the ME-SXR for study of the effects of resonant magnetic perturbation on edge localized modes and the first time neon radiating divertor experiment in EAST are also presented in this work. It has been found that neon impurity can suppress the 2/1 tearing mode and trigger a 3/1 MHD mode.

A study of metalized electrode self-clearing in electroactive polymer (EAP) based actuators

NASA Astrophysics Data System (ADS)

Ahmed, Saad; Ounaies, Zoubeida

2016-04-01

Electroactive polymer (EAP) based technologies have shown promise in areas such as artificial muscles, actuator, aerospace, medical and soft robotics. Still challenges remain such as low induced forces and defects-driven electrical breakdown, which impede the practical implementation of this technology. Multilayered or stacked configuration can address the low induced force issue whereas self-clearing can be a technique to improve breakdown limit of EAP based actuators. Self-clearing refers to the partial local breakdown of dielectric medium due to the presence of impurities, which in turn results in the evaporation of some of the metalized electrode. After this evaporation, the impurity is cleared and any current path would be safely cut off, which means the actuator continues to perform. It is a widely studied concept in the capacitor community, while it has not been studied much for EAP technologies. In this paper we report a systematic approach to precondition a silver-metalized electroactive polymer (EAP), more specifically P(VDF-TrFE-CTFE) terpolymer, using self-clearing concept. First, we show improvement in the dielectric breakdown strength of EAP based unimorph actuators after pre-clearing the impurities using low electric field (lower than dielectric breakdown of the terpolymer). Inspired by this improvement, we used Weibull statistics to systematically estimate the self-clearing/ preconditioning field needed to clear the defects. Then electrical breakdown experiments are conducted with and without preconditioning the samples to investigate its effect on the breakdown strength of the sample.

Impurity effects on ionic-liquid-based supercapacitors

NASA Astrophysics Data System (ADS)

Liu, Kun; Lian, Cheng; Henderson, Douglas; Wu, Jianzhong

2017-02-01

Small amounts of an impurity may affect the key properties of an ionic liquid and such effects can be dramatically amplified when the electrolyte is under confinement. Here the classical density functional theory is employed to investigate the impurity effects on the microscopic structure and the performance of ionic-liquid-based electrical double-layer capacitors, also known as supercapacitors. Using a primitive model for ionic species, we study the effects of an impurity on the double layer structure and the integral capacitance of a room temperature ionic liquid in model electrode pores and find that an impurity strongly binding to the surface of a porous electrode can significantly alter the electric double layer structure and dampen the oscillatory dependence of the capacitance with the pore size of the electrode. Meanwhile, a strong affinity of the impurity with the ionic species affects the dependence of the integral capacitance on the pore size. Up to 30% increase in the integral capacitance can be achieved even at a very low impurity bulk concentration. By comparing with an ionic liquid mixture containing modified ionic species, we find that the cooperative effect of the bounded impurities is mainly responsible for the significant enhancement of the supercapacitor performance.

Impurity Induced Phase Competition and Supersolidity

NASA Astrophysics Data System (ADS)

Karmakar, Madhuparna; Ganesh, R.

2017-12-01

Several material families show competition between superconductivity and other orders. When such competition is driven by doping, it invariably involves spatial inhomogeneities which can seed competing orders. We study impurity-induced charge order in the attractive Hubbard model, a prototypical model for competition between superconductivity and charge density wave order. We show that a single impurity induces a charge-ordered texture over a length scale set by the energy cost of the competing phase. Our results are consistent with a strong-coupling field theory proposed earlier in which superconducting and charge order parameters form components of an SO(3) vector field. To discuss the effects of multiple impurities, we focus on two cases: correlated and random distributions. In the correlated case, the CDW puddles around each impurity overlap coherently leading to a "supersolid" phase with coexisting pairing and charge order. In contrast, a random distribution of impurities does not lead to coherent CDW formation. We argue that the energy lowering from coherent ordering can have a feedback effect, driving correlations between impurities. This can be understood as arising from an RKKY-like interaction, mediated by impurity textures. We discuss implications for charge order in the cuprates and doped CDW materials such as NbSe2.

Dynamic conductivity modified by impurity resonant states in doping three-dimensional Dirac semimetals

NASA Astrophysics Data System (ADS)

Li, Shuai; Wang, Chen; Zheng, Shi-Han; Wang, Rui-Qiang; Li, Jun; Yang, Mou

2018-04-01

The impurity effect is studied in three-dimensional Dirac semimetals in the framework of a T-matrix method to consider the multiple scattering events of Dirac electrons off impurities. It has been found that a strong impurity potential can significantly restructure the energy dispersion and the density of states of Dirac electrons. An impurity-induced resonant state emerges and significantly modifies the pristine optical response. It is shown that the impurity state disturbs the common longitudinal optical conductivity by creating either an optical conductivity peak or double absorption jumps, depending on the relative position of the impurity band and the Fermi level. More importantly, these conductivity features appear in the forbidden region between the Drude and interband transition, completely or partially filling the Pauli block region of optical response. The underlying physics is that the appearance of resonance states as well as the broadening of the bands leads to a more complicated selection rule for the optical transitions, making it possible to excite new electron-hole pairs in the forbidden region. These features in optical conductivity provide valuable information to understand the impurity behaviors in 3D Dirac materials.

Trace Impurity Analysis in Ta Films Using Glow Discharge Mass Spectrometry: Concentration Change of Impurities by Applying Negative Substrate Bias Voltage

NASA Astrophysics Data System (ADS)

Lim, Jae-Won; Mimura, Kouji; Isshiki, Minoru

2004-12-01

Glow discharge mass spectrometry (GDMS) was used to analyze a Ta target and Ta films for trace impurities. The Ta films were deposited on Si (100) substrate at substrate bias voltages of 0 V and -125 V using a non-mass separated ion beam deposition system. Although both Ta films were contaminated by impurities during the deposition, the Ta film deposited at a substrate bias voltage of -125 V showed lower impurity content than the Ta film deposited without the substrate bias voltage, which means that applying a negative bias voltage to the substrate decreased the total concentration of impurities. Furthermore, the concentration change of individual impurities in the Ta film is related to their ionization ratio in the argon discharge plasma. Considering the effect of the ionization potential of an individual impurity on the ionization ratio, purification by applying a negative bias voltage to the substrate results from Penning ionization and an ionization mechanism proposed in this study, as well as from the difference between the kinetic energies of Ta neutral atoms and Ta+ ions accelerated toward the substrate with/without a negative substrate bias voltage.

Scattering of waves by impurities in precompressed granular chains.

PubMed

Martínez, Alejandro J; Yasuda, Hiromi; Kim, Eunho; Kevrekidis, P G; Porter, Mason A; Yang, Jinkyu

2016-05-01

We study scattering of waves by impurities in strongly precompressed granular chains. We explore the linear scattering of plane waves and identify a closed-form expression for the reflection and transmission coefficients for the scattering of the waves from both a single impurity and a double impurity. For single-impurity chains, we show that, within the transmission band of the host granular chain, high-frequency waves are strongly attenuated (such that the transmission coefficient vanishes as the wavenumber k→±π), whereas low-frequency waves are well-transmitted through the impurity. For double-impurity chains, we identify a resonance-enabling full transmission at a particular frequency-in a manner that is analogous to the Ramsauer-Townsend (RT) resonance from quantum physics. We also demonstrate that one can tune the frequency of the RT resonance to any value in the pass band of the host chain. We corroborate our theoretical predictions both numerically and experimentally, and we directly observe almost complete transmission for frequencies close to the RT resonance frequency. Finally, we show how this RT resonance can lead to the existence of reflectionless modes in granular chains (including disordered ones) with multiple double impurities.

Enhanced electron/fuel-ion equilibration through impurity ions: Studies applicable to NIF and Omega

NASA Astrophysics Data System (ADS)

Petrasso, R. D.; Sio, H.; Kabadi, N.; Lahmann, B.; Simpson, R.; Parker, C.; Frenje, J.; Gatu Johnson, M.; Li, C. K.; Seguin, F. H.; Rinderknecht, H.; Casey, D.; Grabowski, P.; Graziani, F.; Taitano, W.; Le, A.; Chacon, L.; Hoffman, N.; Kagan, G.; Simakov, A.; Zylstra, A.; Rosenberg, M.; Betti, R.; Srinivasan, B.; Mancini, R.

2017-10-01

In shock-driven exploding-pushers, a platform used extensively to study multi-species and kinetic effects, electrons and fuel ions are far out of equilibrium, as reflected by very different temperatures. However, impurity ions, even in small quantities, can couple effectively to the electrons, because of a Z2 dependence, and in turn, impurity ions can then strongly couple to the fuel ions. Through this mechanism, electrons and fuel-ions can equilibrate much faster than they otherwise would. This is a quantitative issue, depending upon the amount and Z of the impurity. For NIF and Omega, we consider the role of this process. Coupled non-linear equations, reflecting the temperatures of the three species, are solved for a range of conditions. Consideration is also given to ablatively driven implosions, since impurities can similarly affect the equilibration. This work was supported in part by DOE/NNSA DE-NA0002949 and DE-NA0002726.

Impurity characterization of magnesium diuranate using simultaneous TG-DTA-FTIR measurements

NASA Astrophysics Data System (ADS)

Raje, Naina; Ghonge, Darshana K.; Hemantha Rao, G. V. S.; Reddy, A. V. R.

2013-05-01

Current studies describe the application of simultaneous thermogravimetry-differential thermal analysis - evolved gas analysis techniques for the compositional characterization of magnesium diuranate (MDU) with respect to the impurities present in the matrix. The stoichiometric composition of MDU was identified as MgU2O7ṡ3H2O. Presence of carbonate and sulphate as impurities in the matrix was confirmed through the evolved gas analysis using Fourier Transformation Infrared Spectrometry detection. Carbon and magnesium hydroxide content present as impurities in magnesium diuranate have been determined quantitatively using TG and FTIR techniques and the results are in good agreement. Powder X-ray diffraction analysis of magnesium diuranate suggests the presence of magnesium hydroxide as impurity in the matrix. Also these studies confirm the formation of magnesium uranate, uranium sesquioxide and uranium dioxide above 1000 °C, due to the decomposition of magnesium diuranate.

Impurity effects on electrical conductivity of doped bilayer graphene in the presence of a bias voltage

NASA Astrophysics Data System (ADS)

E, Lotfi; H, Rezania; B, Arghavaninia; M, Yarmohammadi

2016-07-01

We address the electrical conductivity of bilayer graphene as a function of temperature, impurity concentration, and scattering strength in the presence of a finite bias voltage at finite doping, beginning with a description of the tight-binding model using the linear response theory and Green’s function approach. Our results show a linear behavior at high doping for the case of high bias voltage. The effects of electron doping on the electrical conductivity have been studied via changing the electronic chemical potential. We also discuss and analyze how the bias voltage affects the temperature behavior of the electrical conductivity. Finally, we study the behavior of the electrical conductivity as a function of the impurity concentration and scattering strength for different bias voltages and chemical potentials respectively. The electrical conductivity is found to be monotonically decreasing with impurity scattering strength due to the increased scattering among electrons at higher impurity scattering strength.

Levothyroxine sodium revisited: A wholistic structural elucidation approach of new impurities via HPLC-HRMS/MS, on-line H/D exchange, NMR spectroscopy and chemical synthesis.

PubMed

Ruggenthaler, M; Grass, J; Schuh, W; Huber, C G; Reischl, R J

2017-02-20

The structural elucidation of unknown pharmaceutical impurities plays an important role in the quality control of newly developed and well-established active pharmaceutical ingredients (APIs). The United States Pharmacopeia (USP) monograph for the API Levothyroxine Sodium, a synthetic thyroid hormone, features two high pressure liquid chromatography (HPLC) methods using UV-VIS absorption detection to determine organic impurities in the drug substance. The impurity profile of the first USP method ("Procedure 1") has already been extensively studied, however for the second method ("Procedure 2"), which exhibits a significantly different impurity profile, no wholistic structural elucidation of impurities has been performed yet. Applying minor modifications to the chromatographic parameters of USP "Procedure 2" and using various comprehensive structural elucidation methods such as high resolution tandem mass spectrometry with on-line hydrogen-deuterium (H/D) exchange or two-dimensional nuclear magnetic resonance spectroscopy (NMR) we gained new insights about the complex impurity profile of the synthetic thyroid hormone. This resulted in the characterization of 24 compounds previously unknown to literature and the introduction of two new classes of Levothyroxine Sodium impurities. Five novel compounds were unambiguously identified via isolation or synthesis of reference substances and subsequent NMR spectroscopic investigation. Additionally, Collision-Induced Dissociation (CID)-type fragmentation of identified major impurities as well as neutral loss fragmentation patterns of many characterized impurities were discussed. Copyright © 2016 Elsevier B.V. All rights reserved.

Collision of impurities with Bose–Einstein condensates

NASA Astrophysics Data System (ADS)

Lingua, F.; Lepori, L.; Minardi, F.; Penna, V.; Salasnich, L.

2018-04-01

Quantum dynamics of impurities in a bath of bosons is a long-standing problem in solid-state, plasma, and atomic physics. Recent experimental and theoretical investigations with ultracold atoms have focused on this problem, studying atomic impurities immersed in an atomic Bose–Einstein condensate (BEC) and for various relative coupling strengths tuned by the Fano‑Feshbach resonance technique. Here, we report extensive numerical simulations on a closely related problem: the collision between a bosonic impurity consisting of a few 41K atoms and a BEC of 87Rb atoms in a quasi one-dimensional configuration and under a weak harmonic axial confinement. For small values of the inter-species interaction strength (regardless of its sign), we find that the impurity, which starts from outside the BEC, simply causes the BEC cloud to oscillate back and forth, but the frequency of oscillation depends on the interaction strength. For intermediate couplings, after a few cycles of oscillation the impurity is captured by the BEC, and strongly changes its amplitude of oscillation. In the strong interaction regime, if the inter-species interaction is attractive, a local maximum (bright soliton) in the BEC density occurs where the impurity is trapped; if, instead, the inter-species interaction is repulsive, the impurity is not able to enter the BEC cloud and the reflection coefficient is close to one. However, if the initial displacement of the impurity is increased, the impurity is able to penetrate the cloud, leading to the appearance of a moving hole (dark soliton) in the BEC.

Muon spin rotation research program

NASA Technical Reports Server (NTRS)

Stronach, C. E.

1980-01-01

Data from cyclotron experiments and room temperature studies of dilute iron alloys and iron crystals under strain were analyzed. The Fe(Mo) data indicate that the effect upon the contact hyperfine field in Fe due to the introduction of Mo is considerably less than that expected from pure dilution, and the muon (+) are attracted to the Mo impurity sites. There is a significant change in the interstitial magnetic field with Nb concentration. The Fe(Ti) data, for which precession could clearly be observed early only at 468K and above, show that the Ti impurities are attractive to muon (+), and the magnitude of B(hf) is reduced far beyond the amount expected from pure dilution. Changes in the intersitital magnetic field with the introduction of Cr, W, Ge, and Si are also discussed. When strained to the elastic limit, the interstitial magnetic field in Fe crystals is reduced by 33 gauss, and the relaxation rate of the precession signal increases by 47%.

Castellated structures for ITER: Differences of impurity deposition and fuel accumulation in the toroidal and poloidal gaps

NASA Astrophysics Data System (ADS)

Litnovsky, A.; Philipps, V.; Wienhold, P.; Krieger, K.; Kirschner, A.; Borodin, D.; Sergienko, G.; Schmitz, O.; Kreter, A.; Samm, U.; Richter, S.; Breuer, U.; Textor Team

2009-04-01

Castellation is foreseen for the first wall and divertor area in ITER. The concern of the fuel accumulation and impurity deposition in the gaps of castellated structures calls for dedicated studies. Recently, a tungsten castellated limiter with rectangular and roof-like shaped cells was exposed to the SOL plasmas in TEXTOR. After exposure, roughly two times less fuel was found in the gaps between the shaped cells whereas the difference in carbon deposition was less pronounced. Up to 70 at.% of tungsten was found intermixed in the deposited layers in the gaps. The metal fraction in the deposit decreases rapidly with a depth of the gap. Modeling of carbon deposition in poloidal gaps has provided a qualitative agreement with an experiment. The significant anisotropy of C and D distributions in the toroidal gaps was measured.

Graphene Dirac point tuned by ferroelectric polarization field

NASA Astrophysics Data System (ADS)

Wang, Xudong; Chen, Yan; Wu, Guangjian; Wang, Jianlu; Tian, Bobo; Sun, Shuo; Shen, Hong; Lin, Tie; Hu, Weida; Kang, Tingting; Tang, Minghua; Xiao, Yongguang; Sun, Jinglan; Meng, Xiangjian; Chu, Junhao

2018-04-01

Graphene has received numerous attention for future nanoelectronics and optoelectronics. The Dirac point is a key parameter of graphene that provides information about its carrier properties. There are lots of methods to tune the Dirac point of graphene, such as chemical doping, impurities, defects, and disorder. In this study, we report a different approach to tune the Dirac point of graphene using a ferroelectric polarization field. The Dirac point can be adjusted to near the ferroelectric coercive voltage regardless its original position. We have ensured this phenomenon by temperature-dependent experiments, and analyzed its mechanism with the theory of impurity correlation in graphene. Additionally, with the modulation of ferroelectric polymer, the current on/off ratio and mobility of graphene transistor both have been improved. This work provides an effective method to tune the Dirac point of graphene, which can be readily used to configure functional devices such as p-n junctions and inverters.

Modelling of nitrogen seeding experiments in the ASDEX Upgrade tokamak

NASA Astrophysics Data System (ADS)

Casali, L.; Fable, E.; Dux, R.; Ryter, F.; ASDEX Upgrade Team

2018-03-01

Experiments using nitrogen were conducted in H-mode plasmas at ASDEX Upgrade that has a full-W wall. The edge region of H-mode plasmas is modulated by the edge-localized modes (ELMs) which lead to a loss of energy and particles from the confined plasma. In order to gain a better understanding of the complex physical mechanisms which govern the behaviour of radiation and impurities in the presence of ELMs, the evolution of impurities and radiation has been modelled in a time-dependent way. The simulations have been carried out with the ASTRA-STRAHL package featuring the self-consistent interplay between impurity transport, radiation, heat and particle transport of the background plasma, and the effects of ELMs. ELMs are modelled based on the two different assumptions of a diffusive and a convective transport, respectively. The experimental discharge behaviour was reproduced providing only transport coefficients, heat, and particle source. The results underlie the importance of non-coronal effects through the ELM-induced transport which lead to a strong enhancement of the nitrogen radiation. Taking these effects into account is crucial in order to not underestimate the radiation. The radiation properties of high-Z impurities such as tungsten are instead very weakly influenced by non-coronal effects due to its faster equilibration time. While the nitrogen density does not change significantly decreasing the ELM frequency, tungsten density and consequently the radiation increase strongly. The degree to which W is flushed out depends on whether the ELM transport is diffusive or convective. Simulations show that for the N seeded cases considered here, the diffusive model reproduces more accurately the experimental observations. The different behaviour of N and W can be explained in terms of profile peaking which increases with Z (neoclassical pinch). The strong increase in W radiation when the ELM frequency is decreased is not only due to the lack of a sufficiently strong flush out of this impurity but also to the fact that the long time between two crashes gives the impurities time to penetrate further into the plasma escaping the region where they can be flushed out. This is in agreement with the experimental observations and highlights the importance of maintaining high ELM frequencies for the stability and performance of the discharges.

Analysis of neutral beam driven impurity flow reversal in PLT

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

Malik, M.A.; Stacey, W.M. Jr.; Thomas, C.E.

1986-10-01

The Stacey-Sigmar impurity transport theory for tokamak plasmas is applied to the analysis of experimental data from the PLT tokamak with a tungsten limiter. The drag term, which is a central piece in the theory, is evaluated from the recently developed gyroviscous theory for radial momentum transfer. An effort is made to base the modeling of the experiment on measured quantities. Where measured data is not available, recourse is made to extrapolation or numerical modeling. The theoretical and the experimental tungsten fluxes are shown to agree very closely within the uncertainties of the experimental data.

Detection of Amine Impurity and Quality Assessment of the MALDI Matrix α-Cyano-4-Hydroxy-Cinnamic Acid for Peptide Analysis in the amol Range

NASA Astrophysics Data System (ADS)

Rechthaler, Justyna; Pittenauer, Ernst; Schaub, Tanner M.; Allmaier, Günter

2013-05-01

We have studied sample preparation conditions to increase the reproducibility of positive UV-MALDI-TOF mass spectrometry of peptides in the amol range. By evaluating several α-cyano-4-hydroxy-cinnamic acid (CHCA) matrix batches and preparation protocols, it became apparent that two factors have a large influence on the reproducibility and the quality of the generated peptide mass spectra: (1) the selection of the CHCA matrix, which allows the most sensitive measurements and an easier finding of the "sweet spots," and (2) the amount of the sample volume deposited onto the thin crystalline matrix layer. We have studied in detail the influence of a contaminant, coming from commercial CHCA matrix batches, on sensitivity of generated peptide mass spectra in the amol as well as fmol range of a tryptic peptide mixture. The structure of the contaminant, N, N-dimethylbutyl amine, was determined by applying MALDI-FT-ICR mass spectrometry experiments for elemental composition and MALDI high energy CID experiments utilizing a tandem mass spectrometer (TOF/RTOF). A recrystallization of heavily contaminated CHCA batches that reduces or eliminates the determined impurity is described. Furthermore, a fast and reliable method for the assessment of CHCA matrix batches prior to tryptic peptide MALDI mass spectrometric analyses is presented.

Highlights of the Alcator C-Mod Research Campaign

NASA Astrophysics Data System (ADS)

Greenwald, Martin; Alcator Team

2011-10-01

Alcator C-Mod has completed an experimental campaign focusing on broad scientific issues with particular emphasis on ITER needs and requests. Experiments with no NBI torque have investigated spontaneous flow reversal, creation of transport barriers aided by the shear of intrinsic rotation and a variety of RF flow drive schemes. Studies of I-mode have found conditions where a wide operating regime opens up, allowing easy access to long-lived, high-performance discharges with L-mode like particle confinement. We are validating the EPED and BOUT++ models for pedestal height/width and ELM onset using extended parameter scans in ELMy H-mode. The challenge of high-Z impurity generation with ICRF is being addressed first by deployment of a novel antenna whose current straps and antenna box are perpendicular to the total magnetic field -second by studies of the modification of edge impurity transport, where fine-scale Er structures in the SOL in the presence of ICRF heating have been found. LH current drive has produced non-inductive reversed shear regimes at n ~ 5x1019 which exhibit electron temperature ITBs. The first observations have been made of in-tokamak production of divertor tungsten nano-structures (fuzz), which had previously been seen only in linear laboratory experiments. Supported by DoE DE-FC02-99ER54512.

Robustness against non-magnetic impurities in topological superconductors

NASA Astrophysics Data System (ADS)

Nagai, Y.; Ota, Y.; Machida, M.

2014-12-01

We study the robustness against non-magnetic impurities in a three-dimensional topological superconductor, focusing on an effective model (massive Dirac Bogoliubov-de Gennes (BdG) Hamiltonian with s-wave on-site pairing) of CuxBi2Se3 with the parameter set determined by the first-principles calculation. With the use of the self-consistent T- matrix approximation for impurity scattering, we discuss the impurity-concentration dependence of the zero-energy density of states. We show that a single material variable, measuring relativistic effects in the Dirac-BdG Hamiltonian, well characterizes the numerical results. In the nonrelativistic limit, the odd-parity fully-gapped topological superconductivity is fragile against non-magnetic impurities, since this superconductivity can be mapped onto the p-wave superconductivity. On the other hand, in the ultrarelativistic limit, the superconductivity is robust against the non-magnetic impurities, since the effective model has the s-wave superconductivity. We derive the effective Hamiltonian in the both limit.

EMC3-EIRENE modelling of toroidally-localized divertor gas injection experiments on Alcator C-Mod

DOE PAGES

Lore, Jeremy D.; Reinke, M. L.; LaBombard, Brian; ...

2014-09-30

Experiments on Alcator C-Mod with toroidally and poloidally localized divertor nitrogen injection have been modeled using the three-dimensional edge transport code EMC3-EIRENE to elucidate the mechanisms driving measured toroidal asymmetries. In these experiments five toroidally distributed gas injectors in the private flux region were sequentially activated in separate discharges resulting in clear evidence of toroidal asymmetries in radiated power and nitrogen line emission as well as a ~50% toroidal modulation in electron pressure at the divertor target. The pressure modulation is qualitatively reproduced by the modelling, with the simulation yielding a toroidal asymmetry in the heat flow to the outermore » strike point. Finally, toroidal variation in impurity line emission is qualitatively matched in the scrape-off layer above the strike point, however kinetic corrections and cross-field drifts are likely required to quantitatively reproduce impurity behavior in the private flux region and electron temperatures and densities directly in front of the target.« less

Study of the Effects of Impurities on the Properties of Silicon Materials and Performance of Silicon Solar Cell

NASA Technical Reports Server (NTRS)

Sah, C. T.

1979-01-01

Numerical solutions were obtained from the exact one dimensional transmission line circuit model to study the following effects on the terrestrial performance of silicon solar cells: interband Auger recombination; surface recombination at the contact interfaces; enhanced metallic impurity solubility; diffusion profiles; and defect-impurity recombination centers. Thermal recombination parameters of titanium impurity in silicon were estimated from recent experimental data. Based on those parameters, computer model calculations showed that titanium concentration must be kept below 6x10 to the 12th power Ti/cu cm in order to achieve 16% AM1 efficiency in a silicon solar cell of 250 micrometers thick and 1.5 ohm-cm resistivity.

Cryogenic Laser Calorimetry for Impurity Analysis

NASA Technical Reports Server (NTRS)

Swimm, R. T.

1985-01-01

The results of a one-year effort to determine the applicability of laser-calorimetric spectroscopy to the study of deep-level impurities in silicon are presented. Critical considerations for impurity analysis by laser-calorimetric spectroscopy are discussed, the design and performance of a cryogenic laser calorimeter is described, and measurements of background absorption in high-purity silicon are presented.

Numerical Studies of Impurities in Fusion Plasmas

DOE R&D Accomplishments Database

Hulse, R. A.

1982-09-01

The coupled partial differential equations used to describe the behavior of impurity ions in magnetically confined controlled fusion plasmas require numerical solution for cases of practical interest. Computer codes developed for impurity modeling at the Princeton Plasma Physics Laboratory are used as examples of the types of codes employed for this purpose. These codes solve for the impurity ionization state densities and associated radiation rates using atomic physics appropriate for these low-density, high-temperature plasmas. The simpler codes solve local equations in zero spatial dimensions while more complex cases require codes which explicitly include transport of the impurity ions simultaneously with the atomic processes of ionization and recombination. Typical applications are discussed and computational results are presented for selected cases of interest.

Single- or multi-flavor Kondo effect in graphene

NASA Astrophysics Data System (ADS)

Zhu, Zhen-Gang; Ding, Kai-He; Berakdar, Jamal

2010-06-01

Based on the tight-binding formalism, we investigate the Anderson and the Kondo model for an adatom magnetic impurity above graphene. Different impurity positions are analyzed. Employing a partial-wave representation we study the nature of the coupling between the impurity and the conducting electrons. The components from the two Dirac points are mixed while interacting with the impurity. Two configurations are considered explicitly: the adatom is above one atom (ADA), the other case is the adatom above the center the honeycomb (ADC). For ADA the impurity is coupled with one flavor for both A and B sublattice and both Dirac points. For ADC the impurity couples with multi-flavor states for a spinor state of the impurity. We show, explicitly for a 3d magnetic atom, dz2, (dxz,dyz), and (dx2- y2,dxy) couple respectively with the Γ1, Γ5(E1), and Γ6(E2) representations (reps) of C6v group in ADC case. The bases for these reps of graphene are also derived explicitly. For ADA we calculate the Kondo temperature.

Disruption mitigation with high-pressure helium gas injection on EAST tokamak

NASA Astrophysics Data System (ADS)

Chen, D. L.; Shen, B.; Granetz, R. S.; Qian, J. P.; Zhuang, H. D.; Zeng, L.; Duan, Y.; Shi, T.; Wang, H.; Sun, Y.; Xiao, B. J.

2018-03-01

High pressure noble gas injection is a promising technique to mitigate the effect of disruptions in tokamaks. In this paper, results of mitigation experiments with low-Z massive gas injection (helium) on the EAST tokamak are reported. A fast valve has been developed and successfully implemented on EAST, with valve response time  ⩽150 μs, capable of injecting up to 7 × 1022 particles, corresponding to 300 times the plasma inventory. Different amounts of helium gas were injected into stable plasmas in the preliminary experiments. It is seen that a small amount of helium gas (N_He≃ N_plasma ) can not terminate a discharge, but can trigger MHD activity. Injection of 40 times the plasma inventory impurity (N_He≃ 40× N_plasma ) can effectively radiate away part of the thermal energy and make the electron density increase rapidly. The mitigation result is that the current quench time and vertical displacement can both be reduced significantly, without resulting in significantly higher loop voltage. This also reduces the risk of runaway electron generation. As the amount of injected impurity gas increases, the gas penetration time decreases slowly and asymptotes to (˜7 ms). In addition, the impurity gas jet has also been injected into VDEs, which are more challenging to mitigate that stable plasmas.

Nematic superconductivity in CuxBi2Se3 : Surface Andreev bound states

NASA Astrophysics Data System (ADS)

Hao, Lei; Ting, C. S.

2017-10-01

We study theoretically the topological surface states (TSSs) and the possible surface Andreev bound states (SABSs) of CuxBi2Se3 , which is known to be a topological insulator at x =0 . The superconductivity (SC) pairing of this compound is assumed to have broken spin-rotation symmetry, similar to that of the A-phase of 3He as suggested by recent nuclear-magnetic resonance experiments. For both spheroidal and corrugated cylindrical Fermi surfaces with the hexagonal warping terms, we show that the bulk SC gap is rather anisotropic; the minimum of the gap is negligibly small as compared to the maximum of the gap. This would make the fully gapped pairing effectively nodal. For a clean system, our results indicate the bulk of this compound to be a topological superconductor with the SABSs appearing inside the bulk SC gap. The zero-energy SABSs, which are Majorana fermions, together with the TSSs not gapped by the pairing, produce a zero-energy peak in the surface density of states (SDOS). The SABSs are expected to be stable against short-range nonmagnetic impurities, and the local SDOS is calculated around a nonmagnetic impurity. The relevance of our results to experiments is discussed.

Impurity effects on ionic-liquid-based supercapacitors

DOE PAGES

Liu, Kun; Lian, Cheng; Henderson, Douglas; ...

2016-12-27

Small amounts of an impurity may affect the key properties of an ionic liquid and such effects can be dramatically amplified when the electrolyte is under confinement. Here the classical density functional theory is employed to investigate the impurity effects on the microscopic structure and the performance of ionic-liquid-based electrical double-layer capacitors, also known as supercapacitors. Using a primitive model for ionic species, we study the effects of an impurity on the double layer structure and the integral capacitance of a room temperature ionic liquid in model electrode pores and find that an impurity strongly binding to the surface ofmore » a porous electrode can significantly alter the electric double layer structure and dampen the oscillatory dependence of the capacitance with the pore size of the electrode. Meanwhile, a strong affinity of the impurity with the ionic species affects the dependence of the integral capacitance on the pore size. Up to 30% increase in the integral capacitance can be achieved even at a very low impurity bulk concentration. As a result, by comparing with an ionic liquid mixture containing modified ionic species, we find that the cooperative effect of the bounded impurities is mainly responsible for the significant enhancement of the supercapacitor performance.« less

Size, Shape and Impurity Effects on Superconducting critical temperature.

NASA Astrophysics Data System (ADS)

Umeda, Masaki; Kato, Masaru; Sato, Osamu

Bulk superconductors have their own critical temperatures Tc. However, for a nano-structured superconductor, Tc depends on size and shape of the superconductor. Nishizaki showed that the high pressure torsion on bulks of Nb makes Tc higher, because the torsion makes many nano-sized fine grains in the bulks. However the high pressure torsion on bulks of V makes Tc lower, and Nishizaki discussed that the decrease of Tc is caused by impurities in the bulks of V. We studied size, shape, and impurity effects on Tc, by solving the Gor'kov equations, using the finite element method. We found that smaller and narrower superconductors show higher Tc. We found how size and shape affects Tc by studying spacial order parameter distributions and quasi-particle eigen-energies. Also we studied the impurity effects on Tc, and found that Tc decreases with increase of scattering rate by impurities. This work was supported in part of KAKENHI Grant Number JP26400367 and JP16K05460, and program for leading graduate schools of ministry of education, culture, sports, science and technology-Japan.

Identification and accurate quantification of structurally related peptide impurities in synthetic human C-peptide by liquid chromatography-high resolution mass spectrometry.

PubMed

Li, Ming; Josephs, Ralf D; Daireaux, Adeline; Choteau, Tiphaine; Westwood, Steven; Wielgosz, Robert I; Li, Hongmei

2018-06-04

Peptides are an increasingly important group of biomarkers and pharmaceuticals. The accurate purity characterization of peptide calibrators is critical for the development of reference measurement systems for laboratory medicine and quality control of pharmaceuticals. The peptides used for these purposes are increasingly produced through peptide synthesis. Various approaches (for example mass balance, amino acid analysis, qNMR, and nitrogen determination) can be applied to accurately value assign the purity of peptide calibrators. However, all purity assessment approaches require a correction for structurally related peptide impurities in order to avoid biases. Liquid chromatography coupled to high resolution mass spectrometry (LC-hrMS) has become the key technique for the identification and accurate quantification of structurally related peptide impurities in intact peptide calibrator materials. In this study, LC-hrMS-based methods were developed and validated in-house for the identification and quantification of structurally related peptide impurities in a synthetic human C-peptide (hCP) material, which served as a study material for an international comparison looking at the competencies of laboratories to perform peptide purity mass fraction assignments. More than 65 impurities were identified, confirmed, and accurately quantified by using LC-hrMS. The total mass fraction of all structurally related peptide impurities in the hCP study material was estimated to be 83.3 mg/g with an associated expanded uncertainty of 3.0 mg/g (k = 2). The calibration hierarchy concept used for the quantification of individual impurities is described in detail. Graphical abstract ᅟ.

Innovative sludge pretreatment technology for impurity separation using micromesh.

PubMed

Mei, Xiaojie; Han, Xiaomeng; Zang, Lili; Wu, Zhichao

2018-05-23

In order to reduce the impacts on sludge treatment facilities caused by impurities such as fibers, hairs, plastic debris, and coarse sand, an innovative primary sludge pretreatment technology, sludge impurity separator (SIS), was proposed in this study. Non-woven micromesh with pore size of 0.40 mm was used to remove the impurities from primary sludge. Results of lab-scale tests showed that impurity concentration, aeration intensity, and channel gap were the key operation parameters, of which the optimized values were below 25 g/L, 0.8 m 3 /(m 2  min), and 2.5 cm, respectively. In the full-scale SIS with treatment capacity of 300 m 3 /day, over 88% of impurities could be removed from influent and the cleaning cycle of micromesh was more than 16 days. Economic analysis revealed that the average energy consumption was 1.06 kWh/m 3 treated sludge and operation cost was 0.6 yuan/m 3 treated sludge.

Role of codeposited impurities during growth. II. Dependence of morphology on binding and barrier energies

NASA Astrophysics Data System (ADS)

Sathiyanarayanan, Rajesh; Hamouda, Ajmi Bh.; Pimpinelli, A.; Einstein, T. L.

2011-01-01

In an accompanying article we showed that surface morphologies obtained through codeposition of a small quantity (2%) of impurities with Cu during growth (step-flow mode, θ = 40 ML) significantly depends on the lateral nearest-neighbor binding energy (ENN) to Cu adatom and the diffusion barrier (Ed) of the impurity atom on Cu(0 0 1). Based on these two energy parameters, ENN and Ed, we classify impurity atoms into four sets. We study island nucleation and growth in the presence of codeposited impurities from different sets in the submonolayer (θ⩽ 0.7 ML) regime. Similar to growth in the step-flow mode, we find different nucleation and growth behavior for impurities from different sets. We characterize these differences through variations of the number of islands (Ni) and the average island size with coverage (θ). Further, we compute the critical nucleus size (i) for all of these cases from the distribution of capture-zone areas using the generalized Wigner distribution.

VUV spectroscopy in impurity injection experiments at KSTAR using prototype ITER VUV spectrometer.

PubMed

Seon, C R; Hong, J H; Song, I; Jang, J; Lee, H Y; An, Y H; Kim, B S; Jeon, T M; Park, J S; Choe, W; Lee, H G; Pak, S; Cheon, M S; Choi, J H; Kim, H S; Biel, W; Bernascolle, P; Barnsley, R

2017-08-01

The ITER vacuum ultra-violet (VUV) core survey spectrometer has been designed as a 5-channel spectral system so that the high spectral resolving power of 200-500 could be achieved in the wavelength range of 2.4-160 nm. To verify the design of the ITER VUV core survey spectrometer, a two-channel prototype spectrometer was developed. As a subsequent step of the prototype test, the prototype VUV spectrometer has been operated at KSTAR since the 2012 experimental campaign. From impurity injection experiments in the years 2015 and 2016, strong emission lines, such as Kr xxv 15.8 nm, Kr xxvi 17.9 nm, Ne vii 46.5 nm, Ne vi 40.2 nm, and an array of largely unresolved tungsten lines (14-32 nm) could be measured successfully, showing the typical photon number of 10 13 -10 15 photons/cm 2 s.

Integrated Approach for Understanding Impurity Adsorption on Calcite: Mechanisms for Micro-scale Surface Phenomena

NASA Astrophysics Data System (ADS)

Vinson, M. D.; Arvidson, R. S.; Luttge, A.

2004-12-01

A longstanding goal within the field of environmental geochemistry has been the development of a fundamental understanding of the kinetics that governs the interactions of solution-borne impurities with the calcite mineral surface. Recent dissolution experiments using Mg2+, Mn2+, and Sr2+ have shown distinct differences in the interaction of these three impurity ions with the calcite crystal surface. Because the dissolution of carbonate minerals in soils and sediments influences the uptake and migration of groundwater contaminants, a rigorous understanding of the basic processes that occur at the mineral-fluid interface is necessary. We have used vertical scanning interferometry (VSI) coupled with scanning probe microscopy (SPM) to examine calcite crystal dissolution in the presence of Mg2+, Mn2+, and Sr2+, all known dissolution inhibitors and possible groundwater contaminants. We have studied the kinetics of impurity-crystal interactions at a pH 8.8, and in the presence or absence of dissolved inorganic carbon. Our data show that, when individually introduced into undersaturated solutions, Mg2+ and Mn2+ are shown to activate the calcite crystal surface, resulting in enhanced etch pit nucleation rates and step density. Conversely, Sr2+ is shown to cause passivation of the calcite surface. The effect is intensified when solutions are saturated with respect to atmospheric CO2. Results indicate that aqueous CO32- (or HCO3-) may influence how aqueous metal ionic complexes interact with the crystal surface. Furthermore, the influence is differently exhibited, and passivation or activation ultimately depends on the properties of the diffusing metal ion or metal-hydroxide complex. These properties include for example, differences in hydration enthalpy, the effective ionic radius, and electron shell configuration.

The ice VII-ice X phase transition with implications for planetary interiors

NASA Astrophysics Data System (ADS)

Aarestad, B.; Frank, M. R.; Scott, H.; Bricker, M.; Prakapenka, V.

2008-12-01

A significant amount of research on the high pressure polymorphs of H2O have detailed the lattice structure and density of these phases, namely ice VI, ice VII, and ice X. These high pressure ices are noteworthy as they may comprise a considerable part of the interior of large icy planets and satellites. However, there is a dearth of data on how the incorporation of an impurity, charged or non-charged, affects the ice VII-ice X transition. This study examined the ice VII-ice X transition that occurs at approximately 62 GPa with a pure system and two select impure systems. Solutions of pure H2O, 1.6 mole percent NaCl in H2O, and 1.60 mole percent CH3OH in H2O were compressed in a diamond anvil cell (DAC). The experiments were performed at the GSECARS 13-BM-D beam line at the Advanced Photon Source at Argonne National Laboratory. Powder diffraction data of the ice samples were collected using monochromatic X-ray radiation, 0.2755 Å, and a MAR 345 online imaging system at intervals of approximately 2 GPa up to ~71.5, ~74.5, and ~68 GPa, respectively. Analyses of the data provided volume-pressure relations (at 298 K) which were used to detail the ice VII-ice X phase transition. The pressure of the phase transition, based upon an interpretation of the X-ray diffraction data, was found to vary as a function of the impurity type. Thus, the depth of the ice VII-ice X phase transition within an ice-rich planetary body can be influenced by trace-level impurities.

Randomly diluted eg orbital-ordered systems.

PubMed

Tanaka, T; Matsumoto, M; Ishihara, S

2005-12-31

Dilution effects on the long-range ordered state of the doubly degenerate e(g) orbital are investigated. Quenched impurities without the orbital degree of freedom are introduced in the orbital model where the long-range order is realized by the order-from-disorder mechanism. It is shown by Monte Carlo simulations and the cluster-expansion method that a decrease in the orbital-ordering temperature by dilution is substantially larger than that in the randomly diluted spin models. Tilting of orbital pseudospins around impurities is the essence of this dilution effect. The present theory provides a new viewpoint for the recent resonant x-ray scattering experiments in KCu(1-x)Zn(x)F(3).

Kinetic neoclassical transport in the H-mode pedestal

DOE PAGES

Battaglia, D. J.; Burrell, K. H.; Chang, C. S.; ...

2014-07-16

Multi-species kinetic neoclassical transport through the QH-mode pedestal and scrapeoff layer on DIII-D is calculated using XGC0, a 5D full-f particle-in-cell drift-kinetic solver with self-consistent neutral recycling and sheath potentials. We achieved quantitative agreement between the fluxdriven simulation and the experimental electron density, impurity density and orthogonal measurements of impurity temperature and flow profiles by adding random-walk particle diffusion to the guiding-center drift motion. Furthermore, we computed the radial electric field (Er) that maintains ambipolar transport across flux surfaces and to the wall self-consistently on closed and open magnetic field lines, and is in excellent agreement with experiment. The Ermore » inside the separatrix is the unique solution that balances the outward flux of thermal tail deuterium ions against the outward neoclassical electron flux and inward pinch of impurity and colder deuterium ions. Particle transport in the pedestal is primarily due to anomalous transport, while the ion heat and momentum transport is primarily due to the neoclassical transport. The full-f treatment quantifies the non-Maxwellian energy distributions that describe a number of experimental observations in low-collisionallity pedestals on DIII-D, including intrinsic co-Ip parallel flows in the pedestal, ion temperature anisotropy and large impurity temperatures in the scrape-off layer.« less

Quality-by-design approach for the development of telmisartan potassium tablets.

PubMed

Oh, Ga-Hui; Park, Jin-Hyun; Shin, Hye-Won; Kim, Joo-Eun; Park, Young-Joon

2018-05-01

A quality-by-design approach was adopted to develop telmisartan potassium (TP) tablets, which were bioequivalent with the commercially available Micardis ® (telmisartan free base) tablets. The dissolution pattern and impurity profile of TP tablets differed from those of Micardis ® tablets because telmisartan free base is poorly soluble in water. After identifying the quality target product profile and critical quality attributes (CQAs), drug dissolution, and impurities were predicted to be risky CQAs. To determine the exact range and cause of risks, we used the risk assessment (RA) tools, preliminary hazard analysis and failure mode and effect analysis to determine the parameters affecting drug dissolution, impurities, and formulation. The range of the design space was optimized using the face-centered central composite design among the design of experiment (DOE) methods. The binder, disintegrant, and kneading time in the wet granulation were identified as X values affecting Y values (disintegration, hardness, friability, dissolution, and impurities). After determining the design space with the desired Y values, the TP tablets were formulated and their dissolution pattern was compared with that of the reference tablet. The selected TP tablet formulated using design space showed a similar dissolution to that of Micardis ® tablets at pH 7.5. The QbD approach TP tablet was bioequivalent to Micardis ® tablets in beagle dogs.

Impurity profiling of trinitrotoluene using vacuum-outlet gas chromatography-mass spectrometry.

PubMed

Brust, Hanneke; Willemse, Sander; Zeng, Tuoyu; van Asten, Arian; Koeberg, Mattijs; van der Heijden, Antoine; Bolck, Annabel; Schoenmakers, Peter

2014-12-29

In this work, a reliable and robust vacuum-outlet gas chromatography-mass spectrometry (GC-MS) method is introduced for the identification and quantification of impurities in trinitrotoluene (TNT). Vacuum-outlet GC-MS allows for short analysis times; the analysis of impurities in TNT was performed in 4min. This study shows that impurity profiling of TNT can be used to investigate relations between TNT samples encountered in forensic casework. A wide variety of TNT samples were analyzed with the developed method. Dinitrobenzene, dinitrotoluene, trinitrotoluene and amino-dinitrotoluene isomers were detected at very low levels (<1wt.%) by applying the MS in selected-ion monitoring (SIM) mode. Limits of detection ranged from 6ng/mL for 2,6-dinitrotoluene to 43ng/mL for 4-amino-2,6-dinitrotoluene. Major impurities in TNT were 2,4-dinitrotoluene and 2,3,4-trinitrotoluene. Impurity profiles based on seven compounds showed to be useful to TNT samples from different sources. Statistical analysis of these impurity profiles using likelihood ratios demonstrated the potential to investigate whether two questioned TNT samples encountered in forensic casework are from the same source. Copyright © 2014 Elsevier B.V. All rights reserved.

Statistical theory of nucleation in the presence of uncharacterized impurities

NASA Astrophysics Data System (ADS)

Sear, Richard P.

2004-08-01

First order phase transitions proceed via nucleation. The rate of nucleation varies exponentially with the free-energy barrier to nucleation, and so is highly sensitive to variations in this barrier. In practice, very few systems are absolutely pure, there are typically some impurities present which are rather poorly characterized. These interact with the nucleus, causing the barrier to vary, and so must be taken into account. Here the impurity-nucleus interactions are modelled by random variables. The rate then has the same form as the partition function of Derrida’s random energy model, and as in this model there is a regime in which the behavior is non-self-averaging. Non-self-averaging nucleation is nucleation with a rate that varies significantly from one realization of the random variables to another. In experiment this corresponds to variation in the nucleation rate from one sample to another. General analytic expressions are obtained for the crossover from a self-averaging to a non-self-averaging rate of nucleation.

On the Impurity Parameters for Impurities Detected in the Eutectics Co-C and Pt-C and Their Role in the Estimate of the Uncertainty in the Eutectic Temperatures

NASA Astrophysics Data System (ADS)

Bloembergen, Pieter; Dong, Wei; Bai, Cheng-Yu; Wang, Tie-Jun

2011-12-01

In this paper, impurity parameters m i and k i have been calculated for a range of impurities I as detected in the eutectics Co-C and Pt-C, by means of the software package Thermo-Calc within the ternary phase spaces Co-C- I and Pt-C- I. The choice of the impurities is based upon a selection out of the results of impurity analyses performed for a representative set of samples for each of the eutectics in study. The analyses in question are glow discharge mass spectrometry (GDMS) or inductively coupled plasma mass spectrometry (ICP-mass). Tables and plots of the impurity parameters against the atomic number Z i of the impurities will be presented, as well as plots demonstrating the validity of van't Hoff's law, the cornerstone to this study, for both eutectics. For the eutectics in question, the uncertainty u( T E - T liq ) in the correction T E - T liq will be derived, where T E and T liq refer to the transition temperature of the pure system and to the liquidus temperature in the limit of zero growth rate of the solid phase during solidification of the actual system, respectively. Uncertainty estimates based upon the current scheme SIE-OME, combining the sum of individual estimates (SIE) and the overall maximum estimate (OME) are compared with two alternative schemes proposed in this paper, designated as IE-IRE, combining individual estimates (IE) and individual random estimates (IRE), and the hybrid scheme SIE-IE-IRE, combining SIE, IE, and IRE.

Hyperspectral, photogrammetric and morphological characterization of surface impurities over the Greenland ice sheet from remote sensing observations

NASA Astrophysics Data System (ADS)

Tedesco, M.; Alexander, P. M.; Briggs, K.; Linares, M.; Mote, T. L.

2016-12-01

The spatial and temporal evolution of surface impurities over the Greenland ice sheet plays a crucial role in modulating the meltwater production in view of the associated feedback on albedo. Recent studies have pointed to a `darkening' of the west portion of the ice sheet with this reduction in albedo likely associated with the increasing presence of surface impurities (e.g., soot, dust) and biological activity (e.g., cryoconite holes, algae, bacteria). Regional climate models currently do not account for the presence, evolution and impact on albedo of such impurities, mostly because the underlying processes driving the spectral and morphological evolution of impurities are poorly known. One for the reasons for this is the lack of hyperspectral and high-spatial resolution data over specific regions of the Greenland ice sheet. To put things in perspective: there is more hyperspectral data at high spatial resolution for the planet Mars than for the Greenland ice sheet. In this presentation, we report the results of an analysis using the few available hyperspectral data collected over Greenland by the HYPERION and AVIRIS sensors, in conjunction with visible (RGB) helicopter-based high resolution images and LANDSAT/WorldView data for characterizing the spectral and morphological evolution of surface impurities and cryoconite holes over western Greenland. The hyperspectral data is used to characterize the abundance of different `endmembers' and the temporal evolution (inter-seasonal and intra-seasonal) of surface impurities composition and concentration. Digital photographs from helicopter are used to characterize the size and distribution of cryoconite holes as a function of elevation and, lastly, LANDSAT/WV images are used to study the evolution of `mysterious' shapes that form as a consequence of the accumulation of impurities and the ice flow.

Growth of Si spherical crystals and the surface oxidation (M-9)

NASA Technical Reports Server (NTRS)

Nishinaga, Tatau

1993-01-01

Nearly 90 percent of semiconductor devices are produced with Si single crystals as the starting materials. For instance, the integrated circuits (IC), which are used in almost all electronic equipments such as TV, tape recorders, audio amplifiers, etc., are made after various processings of Si single crystal wafers. In these wafers, the same controlled amounts of impurities are added and the uniformities in their distributions are extremely important. Growth under microgravity makes it possible to eliminate the buoyancy-driven convection in the melt, which is one of the main origins of convections which results in non-uniformity of the impurity. Another source of convection is known as Marangoni convection which is driven on the free surface when a temperature gradient occurs. One of the merits of microgravity experimentation is that the detailed study of this convection becomes possible. Another important advantage of microgravity is that growth of crystals without a crucible is possible. This makes it possible to study melt growth without the strain which is usually introduced on the ground. Nevertheless, we should repeat and analyze many growth experiments in space to get reliable results. However, since in the FMPT, the time for the experiment is limited, we plan to carry out two kinds of very simple and basic experiments as the first step for the semiconductor growth experiment. In the first experiment, we use single crystal Si sphere as the starting material and as shown, this sphere is heated in the furnace at a slightly higher temperature than the melting point. After the melting front moves nearly half way to its center, the temperature is decreased to stop the melting and to start the growth from the seed for which we use the unmelted solid party of the sphere. The sphere is centered by quartz protuberances inside of the quartz crucible. There exists the possibility of temperature fluctuations being introduced when the molten sphere occasionally touches the protuberances. The total time needed for the melting and the growth processes is estimated to be 30 minutes. Infrared emission from the sphere is monitored in order to prevent the accidental loss of the central solid core. The schematical illustration of the second experient is shown. A single crystal, Si rod is used as the starting material. In the first stage, the rod is melted from one end to obtain a liquid sphere. In the second stage, the single crystal is grown by decreasing the temperature from the unmelted part of the rod which is used as the seed. The second experient somewhat resembles the Czochralski method used on the ground; however, in the space experiment, no crucible is employed and the temperature uniformity is much superior. In both experiments, phosphorous is doped to allow observation of the change in the shape of the liquid solid interface during crystal growth and the impurity striations, if any.

Perpetual motion and driven dynamics of a mobile impurity in a quantum fluid

NASA Astrophysics Data System (ADS)

Lychkovskiy, O.

2015-04-01

We study the dynamics of a mobile impurity in a quantum fluid at zero temperature. Two related settings are considered. In the first setting, the impurity is injected in the fluid with some initial velocity v0, and we are interested in its velocity at infinite time, v∞. We derive a rigorous upper bound on | v0-v∞| for initial velocities smaller than the generalized critical velocity. In the limit of vanishing impurity-fluid coupling, this bound amounts to v∞=v0 , which can be regarded as a rigorous proof of the Landau criterion of superfluidity. In the case of a finite coupling, the velocity of the impurity can drop, but not to zero; the bound quantifies the maximal possible drop. In the second setting, a small constant force is exerted upon the impurity. We argue that two distinct dynamical regimes exist—backscattering oscillations of the impurity velocity and saturation of the velocity without oscillations. For fluids with vc L=vs (where vc L and vs are the Landau critical velocity and sound velocity, respectively), the latter regime is realized. For fluids with vc L

Surface heat flux feedback controlled impurity seeding experiments with Alcator C-Mod’s high-Z vertical target plate divertor: performance, limitations and implications for fusion power reactors

NASA Astrophysics Data System (ADS)

Brunner, D.; Wolfe, S. M.; LaBombard, B.; Kuang, A. Q.; Lipschultz, B.; Reinke, M. L.; Hubbard, A.; Hughes, J.; Mumgaard, R. T.; Terry, J. L.; Umansky, M. V.; The Alcator C-Mod Team

2017-08-01

The Alcator C-Mod team has recently developed a feedback system to measure and control surface heat flux in real-time. The system uses real-time measurements of surface heat flux from surface thermocouples and a pulse-width modulated piezo valve to inject low-Z impurities (typically N2) into the private flux region. It has been used in C-Mod to mitigate peak surface heat fluxes  >40 MW m-2 down to  <10 MW m-2 while maintaining excellent core confinement, H 98  >  1. While the system works quite well under relatively steady conditions, use of it during transients has revealed important limitations on feedback control of impurity seeding in conventional vertical target plate divertors. In some cases, the system is unable to avoid plasma reattachment to the divertor plate or the formation of a confinement-damaging x-point MARFE. This is due to the small operational window for mitigated heat flux in the parameters of incident plasma heat flux, plasma density, and impurity density as well as the relatively slow response of the impurity gas injection system compared to plasma transients. Given the severe consequences for failure of such a system to operate reliably in a reactor, there is substantial risk that the conventional vertical target plate divertor will not provide an adequately controllable system in reactor-class devices. These considerations motivate the need to develop passively stable, highly compliant divertor configurations and experimental facilities that can test such possible solutions.

Quasibound states in short SNS junctions with point defects

NASA Astrophysics Data System (ADS)

Bespalov, A. A.

2018-04-01

Using the Green functions technique, we study the subgap spectrum of short three-dimensional superconductor-normal metal-superconductor junctions containing one or two point impurities in the normal layer. We find that a single nonmagnetic or magnetic defect induces two quasibound Shiba-like states. If the defect is located close to the junction edge, the energies of these states oscillate as functions of the distance between the impurity and the edge. In the case of two nonmagnetic impurities, there are generally four quasibound states (two per spin projection). Their energies oscillate as functions of the distance between the impurities, and reach their asymptotic values when this distance becomes much larger than the Fermi wavelength. The contributions of the impurities to the Josephson current, local density of states, and to the normal-state conductance of the junction are analyzed.

Trace impurities analysis determined by neutron activation in the PbI 2 crystal semiconductor

NASA Astrophysics Data System (ADS)

Hamada, M. M.; Oliveira, I. B.; Armelin, M. J.; Mesquita, C. H.

2003-06-01

In this work, a methodology for impurity analysis of PbI 2 was studied to investigate the effectiveness of the purification. Commercial salts were purified by the multi passes zone refining and grown by the Bridgman method. To evaluate the purification efficiency, samples from the bottom, middle and upper sections of the ZR ingot were analyzed after 200, 300 and 500 purification passes, by measurements of the impurity concentrations, using the neutron activation analysis (NAA) technique. There was a significant reduction of the impurities according to the purification numbers. The reduction efficiency was different for each element, namely: Au>Mn>Co˜Ag>K˜Br. The impurity concentration of the crystals grown after 200, 300 and 500 passes and the PbI 2 starting material were analyzed by NAA and plasma optical emission spectroscopy.

Influences of temperature and impurity on excited state of bound polaron in the parabolic quantum dots

NASA Astrophysics Data System (ADS)

Xiao, Jing-Lin

2014-06-01

On the condition of strong electron-LO phonon coupling in parabolic quantum dot (QD), the first excited state energy, the excitation energy and the transition frequency between the first excited and the ground states of the bound polaron are calculated by using the linear combination operator and the unitary transformation methods. The variation of the above quantities with the temperature, the Coulombic impurity potential and the QD confinement strength are studied in detail. We find that (1) These physical quantities will increase with increasing temperature. (2) They are increasing functions of the confinement strength due to the existence of the Coulombic impurity potential between the electron and the hydrogen-like impurity. (3) We obtain three ways of tuning them via controlling the temperature, the Coulombic impurity potential and the confinement strength.

Variable-range-hopping magnetoresistance

NASA Astrophysics Data System (ADS)

Azbel, Mark Ya

1991-03-01

The hopping magnetoresistance R of a two-dimensional insulator with metallic impurities is considered. In sufficiently weak magnetic fields it increases or decreases depending on the impurity density n: It decreases if n is low and increases if n is high. In high magnetic fields B, it always exponentially increases with √B . Such fields yield a one-dimensional temperature dependence: lnR~1/ √T . The calculation provides an accurate leading approximation for small impurities with one eigenstate in their potential well. In the limit of infinitesimally small impurities, an impurity potential is described by a generalized function. This function, similar to a δ function, is localized at a point, but, contrary to a δ function in the dimensionality above 1, it has finite eigenenergies. Such functions may be helpful in the study of scattering and localization of any waves.

Oscillatory interaction between O impurities and Al adatoms on Al(111) and its effect on nucleation and growth.

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

Hansen, Henri; Linke, Udo; Feibelman, Peter Julian

2003-07-01

We present a combined experimental and theoretical study of submonolayer growth in the presence of predeposited immobile impurities. Scanning tunneling microscopy measurements of Al/Al(1 1 1) epitaxy in the presence of oxygen adsorbates show that immobile O impurities influence all aspects of the early stages of homoepitaxial growth on Al(1 1 1). Possible scenarios for modified growth are investigated using kinetic Monte Carlo simulations. Dependences of island density on temperature, impurity concentration and strength and type of adatom-impurity interaction are compared. The comparison shows that the morphology of the growing Al film cannot result from only one interaction type: attractivemore » or repulsive. An oscillatory interaction, suggested by ab initio calculations, is proposed to explain the behavior of the system.« less

Effect of accelerated crucible rotation on the segregation of impurities in vertical Bridgman growth of multi-crystalline silicon

NASA Astrophysics Data System (ADS)

Bellmann, M. P.; Meese, E. A.; Arnberg, L.

2011-03-01

We have performed axisymmetric, transient simulations of the vertical Bridgman growth of mc-silicon to study the effect of the accelerated crucible rotation technique (ACRT) on the melt flow and impurity segregation. A solute transport model has been applied to predict the final segregation pattern of impurities in a circular ingot. The sinusoidal ACRT rotation cycle considered here suppresses mixing in the melt near the center, resulting in diffusion-limited mass transport. Therefore the radial impurity segregation is increased towards the center. The effect of increased radial segregation is intensified for low values of the Ekman time scale.

A study of crystal growth by solution technique. [triglycine sulfate single crystals

NASA Technical Reports Server (NTRS)

Lal, R. B.

1979-01-01

The advantages and mechanisms of crystal growth from solution are discussed as well as the effects of impurity adsorption on the kinetics of crystal growth. Uncertainities regarding crystal growth in a low gravity environment are examined. Single crystals of triglycine sulfate were grown using a low temperature solution technique. Small components were assembled and fabricated for future space flights. A space processing experiment proposal accepted by NASA for the Spacelab-3 mission is included.

Symmetry transition via tetravalent impurity and investigations on magnetic properties of Li0.5Fe2.5O4

NASA Astrophysics Data System (ADS)

Kounsalye, Jitendra S.; Kharat, Prashant B.; Chavan, Apparao R.; Humbe, Ashok V.; Borade, R. M.; Jadhav, K. M.

2018-04-01

The present study, deals with the phase symmetry transformation of lithium ferrite after introducing tetravalent (Ti4+) impurity. The sol-gel auto combustion technique was adopted for the synthesis of nanoparticle samples with generic chemical formula Li0.5Fe2.5O4 and Li0.55Ti0.10Fe2.35O4. The synthesized nanoparticles were characterized by X-ray diffraction (XRD) technique for structural analysis. The XRD patterns show the single phase cubic structure without any impurity phase but the P4332 to Fd-3m transformation was observed after introducing Ti4+ impurity. The Nano size of the synthesized particles was confirmed by crystallite size ( 20nm) calculated using Debye-Scherrer's formula. The Fourier transform infrared spectroscopy (FTIR) studies shows shifting of band frequencies which reflect the structural changes after tetravalent substitutional impurities. The magnetic properties were studied through pulse field hysteresis loop (M-H loop) technique at room temperature, the M-H loops showdecrease in magnetic properties afternonmagnetic Ti4+ ion substitution. This is attributed to transition of inverse spinel structure of lithium ferrite to random spinel structure.

Plasma Interactions with Mixed Materials and Impurity Transport

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

Rognlien, T. D.; Beiersdorfer, Peter; Chernov, A.

2016-10-28

The project brings together three discipline areas at LLNL to develop advanced capability to predict the impact of plasma/material interactions (PMI) on metallic surfaces in magnetic fusion energy (MFE) devices. These areas are (1) modeling transport of wall impurity ions through the edge plasma to the core plasma, (2) construction of a laser blow-off (LBO) system for injecting precise amounts of metallic atoms into a tokamak plasma, and (3) material science analysis of fundamental processes that modify metallic surfaces during plasma bombardment. The focus is on tungsten (W), which is being used for the ITER divertor and in designs ofmore » future MFE devices. In area (1), we have worked with the University of California, San Diego (UCSD) on applications of the UEDGE/DUSTT coupled codes to predict the influx of impurity ions from W dust through the edge plasma, including periodic edge-plasma oscillations, and revived a parallel version of UEDGE to speed up these simulations. In addition, the impurity transport model in the 2D UEDGE code has been implemented into the 3D BOUT++ turbulence/transport code to allow fundamental analysis of the impact of strong plasma turbulence on the impurity transport. In area (2), construction and testing of the LBO injection system has been completed. The original plan to install the LBO on the National Spherical Torus Experiment Upgrade (NSTX-U) at Princeton and its use to validate the impurity transport simulations is delayed owing to NSTX-U being offline for substantial magnetic coil repair period. In area (3), an analytic model has been developed to explain the growth of W tendrils (or fuzz) observed for helium-containing plasmas. Molecular dynamics calculations of W sputtering by W and deuterium (D) ions shows that a spatial blending of interatomic potentials is needed to describe the near-surface and deeper regions of the material.« less

Application of photonic crystal defects in constructing all-optical switches, optical delay lines and low-cross-talk waveguide intersections for ultrashort optical pulses

NASA Astrophysics Data System (ADS)

Lan, Sheng; Sugimoto, Yoshimasa; Nishikawa, Satoshi; Ikeda, Naoki; Yang, Tao; Kanamoto, Kozyo; Ishikawa, Hiroshi; Asakawa, Kiyoshi

2002-07-01

We present a systematic study of coupled defects in photonic crystals (PCs) and explore their applications in constructing optical components and devices for ultrafast all-optical signal processing. First, we find that very deep band gaps can be generated in the impurity bands of coupled cavity waveguides (CCWs) by a small periodic modulation of defect modes. This phenomenon implies a high-efficiency all-optical switching mechanism. The switching mechanism can be easily extended from one-dimensional (1D) to two-dimensional and three-dimensional PC structures by utilizing the coupling of defect pairs which are generally present in PCs. Second, we suggest that CCWs with quasiflat and narrow impurity bands can be employed as efficient delay lines for ultrashort pulses. Criteria for designing such kind of CCWs have been derived from the analysis of defect coupling and the investigation of pulse transmission through various CCWs. It is found that the availability of quasiflat impurity bands depends not only on the intrinsic properties of the constituting defects but also on the detailed configuration of CCWs. In experiments, optical delay lines based on 1D monorail CCWs have been successfully fabricated and characterized. Finally, we have proposed a new mechanism for constructing waveguide intersections with broad bandwidth and low cross-talk.

Comparison of resistive MHD simulations and experimental CHI discharges in NSTX

NASA Astrophysics Data System (ADS)

Hooper, E. B.; Sovinec, C. R.; Raman, R.; Fatima, F.

2013-10-01

Resistive MHD simulations using NIMROD simulate CHI discharges for NSTX startup plasmas. Quantitative comparison with experiment ensures that the simulation physics includes a minimal physics set needed to extend the simulations to new experiments, e.g. NSTX-U. Important are time-varying vacuum magnetic field, ohmic heating, thermal transport, impurity radiation, and spatially-varying plasma parameters including density. Equilibria are compared with experimental injector currents, voltages and parameters including toroidal current, photographs of emitted light and measurements of midplane temperature profiles, radiation and surface heating. Initial results demonstrate that adjusting impurity radiation and cross-field transport yields temperatures and injected-current channel widths similar to experiment. These determine the plasma resistance, feeding back to the impedance on the injector power supply. Work performed under the auspices of the U.S. Department of Energy under contracts DE-AC52-07NA27344 at LLNL and DE-AC02-09CH11466 at PPPL, and grants DE-FC02-05ER54813 at PSI Center (U. Wisc.) and DOE-FG02-12ER55115 (at Princeton U.).

Plutonium Extraction by the Formation of Insoluble Salts; EXTRACTION DU PLUTONIUM PAR FORMATION DE SELS INSOLUBLES

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

Ganivet, M.

1960-06-29

The aim of this work is to convert Pu IV nitrate in solution into an insoluble salt. Three methods have been studied: 1) the conventional oxalic acid method was improved; 2) precipitation with 8-hydroxyquinoline was tried; 3) the hydrogen peroxide method was adapted to the eluates of the ionic resins from Marcoule. The yield from the oxalic process has been increased (loss of Pu in the mother-liquor brought from 200 mg/l to 20 mg/l). The study of Pu IV precipitation by 8-hydroxyquinoline has shown that the yield is excellent (Pu concentration in the mother-liquor less than 5 mg/h), but decontaminationmore » from impurities is nil. Finally, experiments on the precipitation by hydrogen peroxide of Pu IV solutions at the concentrations normally obtained from the anionic resins at Marcoule have given us good yields (Pu concentration in the mother-liquor less than 7 mg/l), and the purification is better than that obtained by oxalic acid (1000 ppm total impurities after a precipitation). (author)« less

Dynamical signatures of bound states in waveguide QED

NASA Astrophysics Data System (ADS)

Sánchez-Burillo, E.; Zueco, D.; Martín-Moreno, L.; García-Ripoll, J. J.

2017-08-01

We study the spontaneous decay of an impurity coupled to a linear array of bosonic cavities forming a single-band photonic waveguide. The average frequency of the emitted photon is different from the frequency for single-photon resonant scattering, which perfectly matches the bare frequency of the excited state of the impurity. We study how the energy of the excited state of the impurity influences the spatial profile of the emitted photon. The farther the energy is from the middle of the photonic band, the farther the wave packet is from the causal limit. In particular, if the energy lies in the middle of the band, the wave packet is localized around the causal limit. Besides, the occupation of the excited state of the impurity presents a rich dynamics: it shows an exponential decay up to intermediate times, this is followed by a power-law tail in the long-time regime, and it finally reaches an oscillatory stationary regime. Finally, we show that this phenomenology is robust under the presence of losses, both in the impurity and in the cavities.

Identification and characterization of potential impurities of donepezil.

PubMed

Krishna Reddy, K V S R; Moses Babu, J; Kumar, P Anil; Chandrashekar, E R R; Mathad, Vijayavitthal T; Eswaraiah, S; Reddy, M Satyanarayana; Vyas, K

2004-09-03

Five unknown impurities ranging from 0.05 to 0.2% in donepezil were detected by a simple isocratic reversed-phase high performance liquid chromatography (HPLC). These impurities were isolated from crude sample of donepezil using isocratic reversed-phase preparative high performance liquid chromatography. Based on the spectral data (IR, NMR and MS), the structures of these impurities were characterised as 5,6-dimethoxy-2-(4-pyridylmethyl)-1-indanone (impurity I), 4-(5,6-dimethoxy-2,3-dihydro-1H-2-indenylmethyl) piperidine (impurity II), 2-(1-benzyl-4-piperdylmethyl)-5,6-dimethoxy-1-indanol (impurity III) 1-benzyl-4(5,6-dimethoxy-2,3-dihydro-1H-2-indenylmethyl) piperidine (impurity IV) and 1,1-dibenzyl-4(5,6-dimethoxy-1-oxo-2,3-dihydro-2H-2-indenylmethyl)hexahydropyridinium bromide (impurity V). The synthesis of these impurities and their formation was discussed.

Identification, characterization, synthesis and HPLC quantification of new process-related impurities and degradation products in retigabine.

PubMed

Douša, Michal; Srbek, Jan; Rádl, Stanislav; Cerný, Josef; Klecán, Ondřej; Havlíček, Jaroslav; Tkadlecová, Marcela; Pekárek, Tomáš; Gibala, Petr; Nováková, Lucie

2014-06-01

Two new impurities were described and determined using gradient HPLC method with UV detection in retigabine (RET). Using LC-HRMS, NMR and IR analysis the impurities were identified as RET-dimer I: diethyl {4,4'-diamino-6,6'-bis[(4-fluorobenzyl)amino]biphenyl-3,3'-diyl}biscarbamate and RET-dimer II: ethyl {2-amino-5-[{2-amino-4-[(4-fluorobenzyl) amino] phenyl} (ethoxycarbonyl) amino]-4-[(4-fluorobenzyl)amino] phenyl}carbamate. Reference standards of these impurities were synthesized followed by semipreparative HPLC purification. The mechanism of the formation of these impurities is also discussed. An HPLC method was optimized in order to separate, selectively detect and quantify all process-related impurities and degradation products of RET. The presented method, which was validated in terms of linearity, limit of detection (LOD), limit of quantification (LOQ) and selectivity is very quick (less than 11min including re-equilibration time) and therefore highly suitable for routine analysis of RET related substances as well as stability studies. Copyright © 2014 Elsevier B.V. All rights reserved.

Identification, characterization, and high-performance liquid chromatography quantification of process-related impurities in vonoprazan fumarate.

PubMed

Liu, Lei; Cao, Na; Ma, Xingling; Xiong, Kaihe; Sun, Lili; Zou, Qiaogen

2016-04-01

High-performance liquid chromatography analysis of vonoprazan fumarate, a novel proton pump inhibitor drug revealed six impurities. These were identified by liquid chromatography with mass spectrometry. Further, the structures of the impurities were confirmed by synthesis followed by characterization by mass spectrometry, NMR spectroscopy, and infrared spectroscopy. On the basis of these data and knowledge of the synthetic scheme of vonoprazan fumarate, the previously unknown impurity was identified as 1-[5-(2-fluorophenyl)-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-3-yl]-N-methyldimethylamine, which is a new compound. The possible mechanisms by which these impurities were formed were also discussed. A high-performance liquid chromatography method was optimized in order to separate, selectively detect, and quantify all process-related impurities of vonoprazan fumarate. The presented method has been validated in terms of linearity, limits of detection, and quantification, and response factors and, therefore, is highly suitable for routine analysis of vonoprazan fumarate related substances as well as stability studies. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation of impurity transport using laser blow-off technique in the HL-2A Ohmic and ECRH plasmas

NASA Astrophysics Data System (ADS)

Kai, Zhang; Zheng-Ying, Cui; Ping, Sun; Chun-Feng, Dong; Wei, Deng; Yun-Bo, Dong; Shao-Dong, Song; Min, Jiang; Yong-Gao, Li; Ping, Lu; Qing-Wei, Yang

2016-06-01

Impurity transports in two neighboring discharges with and without electron cyclotron resonance heating (ECRH) are studied in the HL-2A tokamak by laser blow-off (LBO) technique. The progression of aluminium ions as the trace impurity is monitored by soft x-ray (SXR) and bolometer detector arrays with good temporal and spatial resolutions. Obvious difference in the time trace of the signal between the Ohmic and ECRH L-mode discharges is observed. Based on the numerical simulation with one-dimensional (1D) impurity transport code STRAHL, the radial profiles of impurity diffusion coefficient D and convective velocity V are obtained for each shot. The result shows that the diffusion coefficient D significantly increases throughout the plasma minor radius for the ECRH case with respect to the Ohmic case, and that the convection velocity V changes from negative (inward) for the Ohmic case to partially positive (outward) for the ECRH case. The result on HL-2A confirms the pump out effect of ECRH on impurity profile as reported on various other devices.

The development of a potassium-sulfide glass fiber cell and studies on impurities in alkali metal-sulfur cells

NASA Technical Reports Server (NTRS)

Tsang, F. Y.

1977-01-01

Potassium sulfur rechargeable cells, having as the electrolyte the thin walls of hollow glass fibers made from permeable glass, were developed. The cells had short lives, probably due to the construction materials and impurities in the potassium. The effect of the impurities in the analogous NA-S system was studied. Calcium, potassium, and NaOH/oxide impurities caused increased resistance or corrosion of the glass fibers. For long lived cell operation, the Na must contain less than 1 ppm Ca and less than a few ppm of hydroxide/oxide. Up to 150 ppm K can be tolerated. After purification of the Na anolyte, cell lifetimes in excess of 1000 deep charge-discharge cycles or over 8 months on continuous cycling at 10-30 percent depth of discharge were obtained.

Separation and characterization of unknown impurities and isomers in flomoxef sodium by LC-IT-TOF MS and study of their negative-ion fragmentation regularities.

PubMed

Yu, Xu; Wang, Fan; Li, Jiani; Shan, Weiguang; Zhu, Bingqi; Wang, Jian

2017-06-05

Thirteen unknown impurities in flomoxef sodium were separated and characterized by liquid chromatography coupled with high resolution ion trap/time-of-flight mass spectrometry (LC-IT-TOF MS)with positive and negative modes of electrospray ionization method for further improvement of official monographs in pharmacopoeias. The fragmentation patterns of impurities in flomoxef in the negative ion mode were studied in detail, and new negative-ion fragmentation regularities were discovered. Chromatographic separation was performed on a Kromasil C18 column (250mm×4.6mm, 5μm). The mobile phase consisted of (A) ammonium formate aqueous solution (10mM)-methanol (84:16, v/v) and (B) ammonium formate aqueous solution (10mM)-methanol (47:53, v/v). In order to determine the m/z values of the molecular ions and formulas of all detected impurities, full scan LC-MS in both positive and negative ion modes was firstly executed to obtain the m/z value of the molecules. Then LC-MS 2 and LC-MS 3 were carried out on target compounds to obtain as much structural information as possible. Complete fragmentation patterns of impurities were studied and used to obtain information about the structures of these impurities. Structures of thirteen unknown degradation products in flomoxef sodium were deduced based on the high resolution MS n data with both positive and negative modes. The forming mechanisms of degradation products in flomoxef sodium were also studied. Copyright © 2017. Published by Elsevier B.V.

Bose polaron problem: Effect of mass imbalance on binding energy

NASA Astrophysics Data System (ADS)

Ardila, L. A. Peña; Giorgini, S.

2016-12-01

By means of quantum Monte Carlo methods we calculate the binding energy of an impurity immersed in a Bose-Einstein condensate at T =0 . The focus is on the attractive branch of the Bose polaron and on the role played by the mass imbalance between the impurity and the surrounding particles. For an impurity resonantly coupled to the bath, we investigate the dependence of the binding energy on the mass ratio and on the interaction strength within the medium. In particular, we determine the equation of state in the case of a static (infinite mass) impurity, where three-body correlations are irrelevant and the result is expected to be a universal function of the gas parameter. For the mass ratio corresponding to 40K impurities in a gas of 87Rb atoms, we provide an explicit comparison with the experimental findings of a recent study carried out at JILA.

Role of codeposited impurities during growth. I. Explaining distinctive experimental morphology on Cu(0 0 1)

NASA Astrophysics Data System (ADS)

Hamouda, Ajmi Bh.; Sathiyanarayanan, Rajesh; Pimpinelli, Alberto; Einstein, T. L.

2011-01-01

A unified explanation of the physics underlying all the distinctive features of the growth instabilities observed on Cu vicinals has long eluded theorists. Recently, kinetic Monte Carlo studies showed that codeposition of impurities during growth could account for the key distinctive experimental observations [Hamouda , Phys. Rev. BPLRBAQ0556-280510.1103/PhysRevB.77.245430 77, 245430 (2008)]. To identify the responsible impurity atom, we compute the nearest-neighbor binding energies (ENN) and terrace diffusion barriers (Ed) for several candidate impurity atoms on Cu(0 0 1) using DFT-based VASP. Our calculations show that codeposition (with Cu) of midtransition elements, such as Fe, Mn, and W, could—in conjunction with substantial Ehrlich-Schwoebel barriers—cause the observed instabilities; when the experimental setup is considered, W emerges to be the most likely candidate. We discuss the role of impurities in nanostructuring of surfaces.

Dirty two-band superconductivity with interband pairing order

NASA Astrophysics Data System (ADS)

Asano, Yasuhiro; Sasaki, Akihiro; Golubov, Alexander A.

2018-04-01

We study theoretically the effects of random nonmagnetic impurities on the superconducting transition temperature T c in a two-band superconductor characterized by an equal-time s-wave interband pairing order parameter. Because of the two-band degree of freedom, it is possible to define a spin-triplet s-wave pairing order parameter as well as a spin-singlet s-wave order parameter. The former belongs to odd-band-parity symmetry class, whereas the latter belongs to even-band-parity symmetry class. In a spin-singlet superconductor, T c is insensitive to the impurity concentration when we estimate the self-energy due to the random impurity potential within the Born approximation. On the other hand in a spin-triplet superconductor, T c decreases with the increase of the impurity concentration. We conclude that Cooper pairs belonging to odd-band-parity symmetry class are fragile under the random impurity potential even though they have s-wave pairing symmetry.

Role of impurities on the optical properties of rectangular graphene flakes

NASA Astrophysics Data System (ADS)

Sadeq, Z. S.; Muniz, Rodrigo A.; Sipe, J. E.

2018-01-01

We study rectangular graphene flakes using mean field states as the basis for a configuration interaction calculation, which allows us to analyze the low lying electronic excited states including electron correlations beyond the mean field level. We find that the lowest energy transition is polarized along the long axis of the flake, but the charge distributions involved in these transitions are invariably localized on the zigzag edges. We also investigate the impact of both short and long range impurity potentials on the optical properties of these systems. We predict that even a weak impurity localized at a zigzag edge of the flake can have a significant—and often dramatic—effect on its optical properties. This is in contrast to impurities localized at armchair edges or central regions of the flake, for which we predict almost no change to the optical properties of the flake even with strong impurity potentials.

Impurity ion flow and temperature measured in a detached divertor with externally applied non-axisymmetric fields on DIII-D

DOE PAGES

Briesemeister, A. R.; Isler, R. C.; Allen, S. L.; ...

2014-11-15

In this study, externally applied non-axisymmetric magnetic fields are shown to have little effect on the impurity ion flow velocity and temperature as measured by the multichord divertor spectrometer in the DIII-D divertor for both attached and detached conditions. These experiments were performed in H-mode plasmas with the grad-B drift toward the target plates, with and without n = 3 resonant magnetic perturbations (RMPs). The flow velocity in the divertor is shown to change by as much as 30% when deuterium gas puffing is used to create detachment of the divertor plasma. No measurable changes in the C III flowmore » were observed in response to the RMP fields for the conditions used in this work. Images of the C III emission are used along with divertor Thomson scattering to show that the local electron and C III temperatures are equilibrated for the conditions shown.« less

Impurity effects in transition metal silicides

NASA Technical Reports Server (NTRS)

Lien, C.-D.; Nicolet, M.-A.

1984-01-01

Impurities can affect the properties of silicides directly by virtue of their presence. Impurities can also influence the processes by which silicides are formed. The effect of impurities on the reaction of transition metal films with a silicon substrate induced by thermal annealing are well documented. The interpretation of these results is discussed. It is shown that impurity redistribution is a major factor in determining how significant the effect of an impurity is. Redistribution observed for dopant impurities is also discussed.

Entanglement entropy of a three-spin-interacting spin chain with a time-reversal-breaking impurity at one boundary.

PubMed

Nag, Tanay; Rajak, Atanu

2018-04-01

We investigate the effect of a time-reversal-breaking impurity term (of strength λ_{d}) on both the equilibrium and nonequilibrium critical properties of entanglement entropy (EE) in a three-spin-interacting transverse Ising model, which can be mapped to a p-wave superconducting chain with next-nearest-neighbor hopping and interaction. Importantly, we find that the logarithmic scaling of the EE with block size remains unaffected by the application of the impurity term, although, the coefficient (i.e., central charge) varies logarithmically with the impurity strength for a lower range of λ_{d} and eventually saturates with an exponential damping factor [∼exp(-λ_{d})] for the phase boundaries shared with the phase containing two Majorana edge modes. On the other hand, it receives a linear correction in term of λ_{d} for an another phase boundary. Finally, we focus to study the effect of the impurity in the time evolution of the EE for the critical quenching case where the impurity term is applied only to the final Hamiltonian. Interestingly, it has been shown that for all the phase boundaries, contrary to the equilibrium case, the saturation value of the EE increases logarithmically with the strength of impurity in a certain regime of λ_{d} and finally, for higher values of λ_{d}, it increases very slowly dictated by an exponential damping factor. The impurity-induced behavior of EE might bear some deep underlying connection to thermalization.

Entanglement entropy of a three-spin-interacting spin chain with a time-reversal-breaking impurity at one boundary

NASA Astrophysics Data System (ADS)

Nag, Tanay; Rajak, Atanu

2018-04-01

We investigate the effect of a time-reversal-breaking impurity term (of strength λd) on both the equilibrium and nonequilibrium critical properties of entanglement entropy (EE) in a three-spin-interacting transverse Ising model, which can be mapped to a p -wave superconducting chain with next-nearest-neighbor hopping and interaction. Importantly, we find that the logarithmic scaling of the EE with block size remains unaffected by the application of the impurity term, although, the coefficient (i.e., central charge) varies logarithmically with the impurity strength for a lower range of λd and eventually saturates with an exponential damping factor [˜exp(-λd) ] for the phase boundaries shared with the phase containing two Majorana edge modes. On the other hand, it receives a linear correction in term of λd for an another phase boundary. Finally, we focus to study the effect of the impurity in the time evolution of the EE for the critical quenching case where the impurity term is applied only to the final Hamiltonian. Interestingly, it has been shown that for all the phase boundaries, contrary to the equilibrium case, the saturation value of the EE increases logarithmically with the strength of impurity in a certain regime of λd and finally, for higher values of λd, it increases very slowly dictated by an exponential damping factor. The impurity-induced behavior of EE might bear some deep underlying connection to thermalization.

A Spectroscopic Study of Impurity Behavior in Neutral-beam and Ohmically Heated TFTR Discharges

DOE R&D Accomplishments Database

Stratton, B. C.; Ramsey, A. T.; Boody, F. P.; Bush, C. E.; Fonck, R. J.; Groenbner, R. J.; Hulse, R. A.; Richards, R. K.; Schivell, J.

1987-02-01

Quantitative spectroscopic measurements of Z{sub eff}, impurity densities, and radiated power losses have been made for ohmic- and neutral-beam-heated TFTR discharges at a plasma current of 2.2 MA and toroidal field of 4.7 T. Variations in these quantities with line-average plasma density (anti n{sub e}) and beam power up to 5.6 MW are presented for discharges on a graphite movable limiter. A detailed discussion of the use of an impurity transport model to infer absolute impurity densities and radiative losses from line intensity and visible continuum measurements is given. These discharges were dominated by low-Z impurities with carbon having a considerably higher density than oxygen, except in high-anti n{sub e} ohmic discharges, where the densities of carbon and oxygen were comparable. Metallic impurity concentrations and radiative losses were small, resulting in hollow radiated power profiles and fractions of the input power radiated being 30 to 50% for ohmic heating and 30% or less with beam heating. Spectroscopic estimates of the radiated power were in good agreement with bolometrically measured values. Due to an increase in the carbon density, Z{sub eff} rose from 2.0 to 2.8 as the beam power increased from 0 to 5.6 MW, pointing to a potentially serious dilution of the neutron-producing plasma ions as the beam power increased. Both the low-Z and metallic impurity concentrations were approximately constant with minor radius, indicating no central impurity accumulation in these discharges.

Electromagnetically induced transparency in a multilayered spherical quantum dot with hydrogenic impurity

NASA Astrophysics Data System (ADS)

Pavlović, Vladan; Šušnjar, Marko; Petrović, Katarina; Stevanović, Ljiljana

2018-04-01

In this paper the effects of size, hydrostatic pressure and temperature on electromagnetically induced transparency, as well as on absorption and the dispersion properties of multilayered spherical quantum dot with hydrogenic impurity are theoretically investigated. Energy eigenvalues and wavefunctions of quantum systems in three-level and four-level configurations are calculated using the shooting method, while optical properties are obtained using the density matrix formalism and master equations. It is shown that peaks of the optical properties experience a blue-shift with increasing hydrostatic pressure and red-shift with increasing temperature. The changes of optical properties as a consequence of changes in barrier wells widths are non-monotonic, and these changes are discussed in detail.

Magnetic-field-modulated resonant tunneling in ferromagnetic-insulator-nonmagnetic junctions.

PubMed

Song, Yang; Dery, Hanan

2014-07-25

We present a theory for resonance-tunneling magnetoresistance (MR) in ferromagnetic-insulator-nonmagnetic junctions. The theory sheds light on many of the recent electrical spin injection experiments, suggesting that this MR effect rather than spin accumulation in the nonmagnetic channel corresponds to the electrically detected signal. We quantify the dependence of the tunnel current on the magnetic field by quantum rate equations derived from the Anderson impurity model, with the important addition of impurity spin interactions. Considering the on-site Coulomb correlation, the MR effect is caused by competition between the field, spin interactions, and coupling to the magnetic lead. By extending the theory, we present a basis for operation of novel nanometer-size memories.

Electromagnetically Induced Transparency Experiments for the Advanced Undergraduate Laboratory: Suppression of Polarization Impurity and Stray Magnetic Fields

NASA Astrophysics Data System (ADS)

Campbell, Kaleb; Jackson, Richard; van Vleet, Matthew; Kuhnash, Kodi; Worth, Bradley; Day, Amanda; Bali, Samir

2014-05-01

We investigate electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) in rubidium vapor using a single laser beam and a scanning magnetic field co-aligned with the laser propagation direction. We show that polarization impurity, stray magnetic fields and imperfect optical alignments cause broadening of the EIT/EIA signal and other spurious effects. We describe a systematic approach to minimizing these undesired effects, which produces EIT/EIA signals nearly two orders of magnitude narrower than the natural linewidth. We gratefully acknowledge funding from the American Chemical Society Petroleum Research Fund and Miami University. We also acknowledge the Miami University Instrumentation Laboratory for their invaluable contributions.

Does the physics of (Ga,Mn)N differ from (GaMn)As qualitatively or quantitatively? Is valance of Mn impurity 2+ or 3+?

NASA Astrophysics Data System (ADS)

Nelson, Ryky; Berlijn, Tom; Ku, Wei; Moreno, Juana; Jarrell, Mark

2013-03-01

(Ga,Mn)N is a promising material for spintronics due to its potential high currie temperature (Tc). However, unlike for (Ga,Mn)As, some of the experiments on (Ga,Mn)N are still controversial on the intrinsic nature of the magnetism. Furthermore, under debate are the spin and charge state of the disordered Mn impurities in (Ga,Mn)N and whether its local moments interact via the same exchange mechanism as in (Ga,Mn)As. To address these issues we will present ab-initio-based analyses of disorder and correlation via the recently developed Wannier function based methods.

The effect of structurally related impurities on crystallinity reduction of sulfamethazine by grinding.

PubMed

Hamada, Yoshito; Ono, Makoto; Ohara, Motomu; Yonemochi, Etsuo

2016-12-30

In this study, the effect of structurally related impurities on crystallinity reduction of sulfamethazine by grinding was evaluated. The crystallinity of sulfamethazine was not decreased when it was ground alone. However, when structurally related impurities with sulfonamide derivatives were blended, the crystallinity of sulfamethazine was decreased by grinding. Other materials without a sulfonamide moiety showed no such effect. The Raman spectra of sulfamethazine demonstrated that there was a difference between its crystalline and amorphous states within its sulfonamide structure. It was suggested that the sulfonamide structure of the impurities was important in causing the inhibition of recrystallization of sulfamethazine during grinding. Copyright © 2016 Elsevier B.V. All rights reserved.

Impurity-induced states in superconducting heterostructures

NASA Astrophysics Data System (ADS)

Liu, Dong E.; Rossi, Enrico; Lutchyn, Roman M.

2018-04-01

Heterostructures allow the realization of electronic states that are difficult to obtain in isolated uniform systems. Exemplary is the case of quasi-one-dimensional heterostructures formed by a superconductor and a semiconductor with spin-orbit coupling in which Majorana zero-energy modes can be realized. We study the effect of a single impurity on the energy spectrum of superconducting heterostructures. We find that the coupling between the superconductor and the semiconductor can strongly affect the impurity-induced states and may induce additional subgap bound states that are not present in isolated uniform superconductors. For the case of quasi-one-dimensional superconductor/semiconductor heterostructures we obtain the conditions for which the low-energy impurity-induced bound states appear.

Application of a trap-free two-dimensional liquid chromatography combined with ion trap/time-of-flight mass spectrometry for separation and characterization of impurities and isomers in cefpiramide.

PubMed

Wang, Jian; Xu, Yu; Wen, Chunmei; Wang, Zhijian

2017-11-01

High-resolution mass spectrometry had been routinely used for structure identification of impurity. However, all LC-MS methods were based on a volatile mobile phase, and a non-volatile system is used in the official analytical method of United States Pharmacopoeia for cefpiramide which limited the use of mass spectrometry for structure characterization of the impurities. Here we presented the utilization of a trap-free two-dimensional liquid chromatography coupled to high resolution ion trap/time-of-flight mass spectrometry (2D LC-IT-TOF MS) with positive and negative modes of electrospray ionization for characterization of eight impurities in cefpiramide. Trap-free two-dimensional liquid chromatography and online desalting technique made it possible to characterize the impurity in cefpiramide in the condition of official standard, and the TIC chromatogram of LC-MS was in conformity with the LC chromatogram of the official analytical method in the peak sequence of impurities, which could further improve the method of official monographs in pharmacopoeias. Each peak separated by the non-volatile mobile phase was trapped by a 20 μL quantitative loop then transferred into a system with a volatile mobile phase connected to a MS detector. In the first dimension, the column was Kromasil C 8 analytical column (250 mm × 4.6 mm, 5 μm) with a non-volatile salt mobile phase at the flow rate of 0.8 mL min -1 . In the second dimension, the column was Shimadzu Shim-pack GISS C 18 (50 mm × 2.1 mm, 1.9 μm) with a volatile salt mobile phase at the flow rate of 0.3 mL min -1 . Through the multiple heart-cutting 2D-LC approach and online desalting technique, the problem of incompatibility between non-volatile salt mobile phase and mass spectrometry was solved completely. The fragmentation behavior of cefpiramide and its eight impurities were studied. The structures of eight impurities in cefpiramide drug substance were deduced based on the HPLC-MS n data, in which seven impurities were novel impurities. The forming mechanisms of degradation products in cefpiramide were also studied. Copyright © 2017 Elsevier B.V. All rights reserved.

Computational Design and Prototype Evaluation of Aluminide-Strengthened Ferritic Superalloys for Power-Generating Turbine Applications up to 1,033 K

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

Peter Liaw; Gautam Ghosh; Mark Asta

2010-04-30

The objective of the proposed research is to utilize modern computational tools, integrated with focused experiments, to design innovative ferritic NiAl-strengthened superalloys for fossil-energy applications at temperatures up to 1,033 K. Specifically, the computational alloy design aims toward (1) a steady-state creep rate of approximately 3 x 10{sup -11} s{sup -1} at a temperature of 1,033 K and a stress level of 35 MPa, (2) a ductility of 10% at room temperature, and (3) good oxidation and corrosion resistance at 1,033 K. The research yielded many outstanding research results, including (1) impurity-diffusion coefficients in {alpha} Fe have been calculated bymore » first principles for a variety of solute species; (2) the precipitates were characterized by the transmission-electron microscopy (TEM) and analytical-electron microscopy (AEM), and the elemental partitioning has been determined; (3) a bending ductility of more than 5% has been achieved in the unrolled materials; and (4) optimal compositions with minimal secondary creep rates at 973 K have been determined. Impurity diffusivities in {alpha} Fe have been calculated within the formalisms of a harmonic transition-state theory and Le Claire nine-frequency model for vacancy-mediated diffusion. Calculated diffusion coefficients for Mo and W impurities are comparable to or larger than that for Fe self-diffusion. Calculated activation energies for Ta and Hf impurities suggest that these solutes should display impurity-diffusion coefficients larger than that for self-diffusion in the body-centered cubic Fe. Preliminary mechanical-property studies identified the alloy Fe-6.5Al-10Ni-10Cr-3.4Mo-0.25Zr-0.005B (FBB-8) in weight percent (wt.%) for detailed investigations. This alloy shows precipitation of NiAl particles with an average diameter of 130 nm. In conjunction with the computational alloy design, selected experiments are performed to investigate the effect of the Al content on the ductility and creep of prototype Fe-Ni-Cr-Al-Mo alloys. Three-point-bending experiments show that alloys containing more than 5 wt.% Al exhibit poor ductility (< 2%) at room temperature, and their fracture mode is predominantly of a cleavage type. Two major factors governing the poor ductility are (1) the volume fraction of NiAl-type precipitates, and (2) the Al content in the {alpha}-Fe matrix. A bend ductility of more than 5% can be achieved by lowering the Al concentration to 3 wt.% in the alloy. The alloy containing about 6.5 wt.% Al is found to have an optimal combination of hardness, ductility, and minimal creep rate at 973 K. A high volume fraction of precipitates is responsible for the good creep resistance by effectively resisting the dislocation motion through Orowan-bowing and dislocation-climb mechanisms. The effects of stress on the creep rate have been studied. With the threshold-stress compensation, the stress exponent is determined to be 4, indicating power-law dislocation creep. The threshold stress is in the range of 40-53 MPa. The addition of W can significantly reduce the secondary creep rates. Compared to other candidates for steam-turbine applications, FBB-8 does not show superior creep resistance at high stresses (> 100 MPa), but exhibit superior creep resistance at low stresses (< 60 MPa).« less

Identification, isolation, and synthesis of seven novel impurities of anti-diabetic drug Repaglinide.

PubMed

Kancherla, Prasad; Keesari, Srinivas; Alegete, Pallavi; Khagga, Mukkanti; Das, Parthasarathi

2018-01-01

Seven unknown impurities in Repaglinide bulk drug batches at below 0.1% (ranging from 0.05 to 0.10%) were detected by an ultra-performance liquid chromatographic (UPLC) method. These impurities were isolated from the crude sample of Repaglinide using preparative high performance liquid chromatography (prep-HPLC). Based on liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI/MS) study, the chemical structures of seven new impurities (8, 9, 10, 11, 13, 14, and 16) were presumed and characterized as 4-(cyanomethyl)-2-ethoxybenzoic acid (8), 4-(cyanomethyl)-2-ethoxy-N-(3-methyl-1-(2-(piperidin-1-yl)phenyl)butyl)benzamide (9), 4-(2-amino-2-oxoethyl)-2-ethoxy-N-(3-methyl-1-(2-(piperidin-1-yl)phenyl)butyl) benzamide (10) and 2-(3-ethoxy-4-((3-methyl-1-(2-(piperidin-1-yl)phenyl)butyl) carbamoyl) phenyl) acetic acid (11) and 4-(cyanomethyl)-N-cyclohexyl-2-ethoxybenzamide (13), 2-(4-(cyclohexylcarbamoyl)-3-ethoxyphenyl) acetic acid (14) and N-cyclohexyl-4-(2-(cyclohexylamino)-2-oxoethyl)-2-ethoxybenzamide (16). The complete spectral analysis, proton nuclear magnetic resonance ( 1 H NMR), 13 C NMR, MS, and infrared (IR) confirmed the proposed chemical structures of impurities. Identification, structural characterization, formation, and their synthesis was first reported in this study. The impurity 11 was crystallized and structure was solved by single crystal X-ray diffraction. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

CE-UV/VIS and CE-MS for monitoring organic impurities during the downstream processing of fermentative-produced lactic acid from second-generation renewable feedstocks.

PubMed

Laube, Hendrik; Matysik, Frank-Michael; Schmidberger, Andreas; Mehlmann, Kerstin; Toursel, Andreas; Boden, Jana

2016-01-01

During the downstream process of bio-based bulk chemicals, organic impurities, mostly residues from the fermentation process, must be separated to obtain a pure and ready-to-market chemical. In this study, capillary electrophoresis was investigated for the non-targeting downstream process monitoring of organic impurities and simultaneous quantitative detection of lactic acid during the purification process of fermentatively produced lactic acid. The downstream process incorporated 11 separation units, ranging from filtration, adsorption and ion exchange to electrodialysis and distillation, and 15 different second-generation renewable feedstocks were processed into lactic acid. The identification of organic impurities was established through spiking and the utilization of an advanced capillary electrophoresis mass spectrometry system. A total of 53 % of the organic impurities were efficiently removed via bipolar electrodialysis; however, one impurity, pyroglutamic acid, was recalcitrant to separation. It was demonstrated that the presence of pyroglutamic acid disrupts the polymerization of lactic acid into poly lactic acid. Pyroglutamic acid was present in all lactic acid solutions, independent of the type of renewable resource or the bacterium applied. Pyroglutamic acid, also known as 5-oxoproline, is a metabolite in the glutathione cycle, which is present in all living microorganisms. pyroglutamic acid is found in many proteins, and during intracellular protein metabolism, N-terminal glutamic acid and glutamine residues can spontaneously cyclize to become pyroglutamic acid. Hence, the concentration of pyroglutamic acid in the lactic acid solution can only be limited to a certain amount. The present study proved the capillary electrophoresis system to be an important tool for downstream process monitoring. The high product concentration encountered in biological production processes did not hinder the capillary electrophoresis from separating and detecting organic impurities, even at minor concentrations. The coupling of the capillary electrophoresis with a mass spectrometry system allowed for the straightforward identification of the remaining critical impurity, pyroglutamic acid. Although 11 separation units were applied during the downstream process, the pyroglutamic acid concentration remained at 12,900 ppm, which was comparatively high. All organic impurities found were tracked by the capillary electrophoresis, allowing for further separation optimization.

Probing and Manipulating Ultracold Fermi Superfluids

NASA Astrophysics Data System (ADS)

Jiang, Lei

Ultracold Fermi gas is an exciting field benefiting from atomic physics, optical physics and condensed matter physics. It covers many aspects of quantum mechanics. Here I introduce some of my work during my graduate study. We proposed an optical spectroscopic method based on electromagnetically-induced transparency (EIT) as a generic probing tool that provides valuable insights into the nature of Fermi paring in ultracold Fermi gases of two hyperfine states. This technique has the capability of allowing spectroscopic response to be determined in a nearly non-destructive manner and the whole spectrum may be obtained by scanning the probe laser frequency faster than the lifetime of the sample without re-preparing the atomic sample repeatedly. Both quasiparticle picture and pseudogap picture are constructed to facilitate the physical explanation of the pairing signature in the EIT spectra. Motivated by the prospect of realizing a Fermi gas of 40K atoms with a synthetic non-Abelian gauge field, we investigated theoretically BEC-HCS crossover physics in the presence of a Rashba spin-orbit coupling in a system of two-component Fermi gas with and without a Zeeman field that breaks the population balance. A new bound state (Rashba pair) emerges because of the spin-orbit interaction. We studied the properties of Rashba pairs using a standard pair fluctuation theory. As the two-fold spin degeneracy is lifted by spin-orbit interaction, bound pairs with mixed singlet and triplet pairings (referred to as rashbons) emerge, leading to an anisotropic superfluid. We discussed in detail the experimental signatures for observing the condensation of Rashba pairs by calculating various physical observables which characterize the properties of the system and can be measured in experiment. The role of impurities as experimental probes in the detection of quantum material properties is well appreciated. Here we studied the effect of a single classical impurity in trapped ultracold Fermi superfluids. Although a non-magnetic impurity does not change macroscopic properties of s-wave Fermi superfluids, depending on its shape and strength, a magnetic impurity can induce single or multiple mid-gap bound states. The multiple mid-gap states could coincide with the development of a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase within the superfluid. As an analog of the Scanning Tunneling Microscope, we proposed a modified radio frequency spectroscopic method to measure the focal density of states which can be employed to detect these states and other quantum phases of cold atoms. A key result of our self consistent Bogoliubov-de Gennes calculations is that a magnetic impurity can controllably induce an FFLO state at currently accessible experimental parameters.

Solution of effective Hamiltonian of impurity hopping between two sites in a metal

NASA Astrophysics Data System (ADS)

Ye, Jinwu

1998-03-01

We analyze in detail all the possible fixed points of the effective Hamiltonian of a non-magnetic impurity hopping between two sites in a metal obtained by Moustakas and Fisher(MF). We find a line of non-fermi liquid fixed points which continuously interpolates between the 2-channel Kondo fixed point(2CK) and the one channel, two impurity Kondo (2IK) fixed point. There is one relevant direction with scaling dimension 1/2 and one leading irrelevant operator with dimension 3/2. There is also one marginal operator in the spin sector moving along this line. The additional non-fermi liquid fixed point found by MF has the same symmetry as the 2IK, it has two relevant directions with scaling dimension 1/2, therefore also unstable. The system is shown to flow to a line of fermi-liquid fixed points which continuously interpolates between the non-interacting fixed point and the 2 channel spin-flavor Kondo fixed point (2CSFK) discussed by the author previously. The effect of particle-hole symmetry breaking is discussed. The effective Hamiltonian in the external magnetic field is analysed. The scaling functions for the physical measurable quantities are derived in the different regimes; their predictions for the experiments are given. Finally the implications are given for a non-magnetic impurity hopping around three sites with triangular symmetry discussed by MF.

Quality by design (QbD) based development and validation of an HPLC method for amiodarone hydrochloride and its impurities in the drug substance.

PubMed

Karmarkar, S; Yang, X; Garber, R; Szajkovics, A; Koberda, M

2014-11-01

The USP monograph describes an HPLC method for seven impurities in the amiodarone drug substance using a L1 column, 4.6mm×150mm, 5μm packing (PF listed ODS2 GL-Science, Inertsil column) at 30°C with detection at 240nm. The standard contains 0.01mg/mL of amiodarone, and USP specified impurities D and E with a resolution requirement of NLT 3.5 between peaks D and E. Impurities in a 5mg/mL sample are quantitated against the standard. Impurity A peak elutes just before peak D. We observed two problems with the method; the column lot-to-lot variability resulted in unresolved A, D, and E peaks, and peak D in the sample preparation eluted much later than that in the standard solution. Therefore, optimization experiments were conducted on the USP method following the QbD approach with Fusion AE™ software (S-Matrix Corporation). The resulting optimized conditions were within the allowable changes per USP 〈621〉. Lot-to-lot variability was negligible with the Atlantis T3 (Waters Corporation) L1 column. Peak D retention time remained constant from standard to sample. The optimized method was validated in terms of accuracy, precision, linearity, range, LOQ/LOD, specificity, robustness, equivalency to the USP method, and solution stability. The QbD based development helped in generating a design space and operating space with knowledge of all method performance characteristics and limitations and successful method robustness within the operating space. Copyright © 2014 Elsevier B.V. All rights reserved.

Local gas injection as a scrape-off layer diagnostic on the Alcator C-Mod tokamak

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

Jablonski, David F.

1996-05-01

A capillary puffing array has been installed on Alcator C-Mod which allows localized introduction of gaseous species in the scrape-off layer. This system has been utilized in experiments to elucidate both global and local properties of edge transport. Deuterium fueling and recycling impurity screening are observed to be characterized by non-dimensional screening efficiencies which are independent of the location of introduction. In contrast, the behavior of non-recycling impurities is seen to be characterized by a screening time which is dependent on puff location. The work of this thesis has focused on the use of the capillary array with a cameramore » system which can view impurity line emission plumes formed in the region of an injection location. The ionic plumes observed extend along the magnetic field line with a comet-like asymmetry, indicative of background plasma ion flow. The flow is observed to be towards the nearest strike-point, independent of x-point location, magnetic field direction, and other plasma parameters. While the axes of the plumes are generally along the field line, deviations are seen which indicate cross-field ion drifts. A quasi-two dimensional fluid model has been constructed to use the plume shapes of the first charge state impurity ions to extract information about the local background plasma, specifically the temperature, parallel flow velocity, and radial electric field. Through comparisons of model results with those of a three dimensional Monte Carlo code, and comparisons of plume extracted parameters with scanning probe measurements, the efficacy of the model is demonstrated. Plume analysis not only leads to understandings of local edge impurity transport, but also presents a novel diagnostic technique.« less

Impurity-induced divertor plasma oscillations

DOE PAGES

Smirnov, R. D.; Kukushkin, A. S.; Krasheninnikov, S. I.; ...

2016-01-07

Two different oscillatory plasma regimes induced by seeding the plasma with high- and low-Z impurities are found for ITER-like divertor plasmas, using computer modeling with the DUSTT/UEDGE and SOLPS4.3 plasma-impurity transport codes. The oscillations are characterized by significant variations of the impurity-radiated power and of the peak heat load on the divertor targets. Qualitative analysis of the divertor plasma oscillations reveals different mechanisms driving the oscillations in the cases of high- and low-Z impurity seeding. The oscillations caused by the high-Z impurities are excited near the X-point by an impurity-related instability of the radiation-condensation type, accompanied by parallel impurity ionmore » transport affected by the thermal and plasma friction forces. The driving mechanism of the oscillations induced by the low-Z impurities is related to the cross-field transport of the impurity atoms, causing alteration between the high and low plasma temperature regimes in the plasma recycling region near the divertor targets. As a result, the implications of the impurity-induced plasma oscillations for divertor operation in the next generation tokamaks are also discussed.« less

Systematic study of electronic and magnetic properties for Cu{sub 12–x}TM{sub x}Sb{sub 4}S{sub 13} (TM = Mn, Fe, Co, Ni, and Zn) tetrahedrite

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

Suekuni, K., E-mail: ksuekuni@hiroshima-u.ac.jp; Tomizawa, Y.; Ozaki, T.

2014-04-14

Substitution effects of 3d transition metal (TM) impurities on electronic and magnetic properties for Cu{sub 12}Sb{sub 4}S{sub 13} tetrahedrite are investigated by the combination of low-temperature experiments and first-principles electronic-structure calculations. The electrical resistivity for the cubic phase of Cu{sub 12}Sb{sub 4}S{sub 13} exhibits metallic behavior due to an electron-deficient character of the compound. Whereas that for 0.5 ≤ x ≤ 2.0 of Cu{sub 12−x}Ni{sub x}Sb{sub 4}S{sub 13} exhibits semiconducting behavior. The substituted Ni for Cu is in the divalent ionic state with a spin magnetic moment and creates impurity bands just above the Fermi level at the top of the valence band. Therefore,more » the semiconducting behavior of the electrical resistivity is attributed to the thermal excitation of electrons from the valence band to the impurity band. The substitution effect of TM on the electronic structure and the valency of TM for Cu{sub 11.0}TM{sub 1.0}Sb{sub 4}S{sub 13} are systematically studied by the calculation. The substituted Mn, Fe, and Co for Cu are found to be in the ionic states with the spin magnetic moments due to the large exchange splitting of the 3d bands between the minority- and majority-spin states.« less

An experimental study on the cavitation of water with dissolved gases

NASA Astrophysics Data System (ADS)

Li, Buxuan; Gu, Youwei; Chen, Min

2017-12-01

Cavitation inception is generally determined by the tensile strengths of liquids. Investigations on the tensile strength of water, which is essential in many fields, will help understand the promotion/prevention of cavitation and related applications in water. Previous experimental studies, however, vary in their conclusions about the value of tensile strength of water; the difference is commonly attributed to the existence of impurities in water. Dissolved gases, especially oxygen and nitrogen from the air, are one of the most common kinds of impurities in water. The influence of these gases on the tensile strength of water is still unclear. This study investigated the effects of dissolved gases on water cavitation through experiments. Cavitation in water is generated by acoustic method. Water samples are prepared with dissolved oxygen and nitrogen in different gas concentrations. Results show that under the same temperature, the tensile strength of water with dissolved oxygen or nitrogen decreases with increased gas concentration compared with that of ultrapure water. Under the same gas concentration and temperature, water with dissolved oxygen shows a lower tensile strength than that with dissolved nitrogen. Possible reasons of these results are also discussed.

The effect of relative solubility on crystal purity

NASA Astrophysics Data System (ADS)

Givand, Jeffrey Christopher

This study establishes the relationship between impurity incorporation in a crystal by lattice substitution and the solubility of that impurity in solution. The model system studied was L-isoleucine crystals contaminated by the isomorphic impurity L-leucine. Upon crystallization from aqueous solution by cooling, leucine is concentrated in the isoleucine unit cell through lattice substitution mechanisms. Attempts to reduce the degree of leucine incorporation via adjustments of the rate at which supersaturation is generated yielded marginal success. This work demonstrates that incorporation of leucine in the crystal can be considerably suppressed by reducing the solubility of product relative to the solubility of impurity. Changes to the relative solubility of the impurity were accomplished by the addition of various electrolytes and organic co-solvents to the aqueous amino acid solutions. The solubilities of the two amino acids were measured and compared to their solubilities in pure water. Changes in the ratio of pure-component solubilities were directly related to changes in crystal purity. This thermodynamic quantity of relative solubility was shown to be a key factor in determining impurity uptake by lattice substitution. In addition to the experimental observations, a fundamental thermodynamic link between relative solubility and crystal purity is established through this research. First, the amino acid solubility data as a function of temperature in all solvent mixtures were accurately correlated using a thermodynamic model. The parameters from this model were then adapted to a novel solid-solution thermodynamic model to express the crystal purity in terms of equilibrium solution impurity concentration. After the determination of one system specific parameter, the model is able to predict the crystal purity in a new solvent in which the pure-component solubilities are known. The ability of an electrolyte or co-solvent to improve crystal purity from a given level can now be determined based on existing solubility and purity measurements and solubilities of the product and impurity in the new solvent mixture.

Identification, synthesis and structural characterization of process related and degradation impurities of acrivastine and validation of HPLC method.

PubMed

Kumar, Ajay; Devineni, Subba Rao; Dubey, Shailender Kumar; Kumar, Pradeep; Srivastava, Vishal; Ambulgekar, Girish; Jain, Mohit; Gupta, Dharmendra Kumar; Singh, Gurmeet; Kumar, Rajesh; Hiriyanna, S G; Kumar, Pramod

2016-10-17

Four impurities (Imp-I-IV) were detected using gradient HPLC method in few laboratory batches of acrivastine in the level of 0.03-0.12% and three impurities (Imp-I-III) were found to be known and one (Imp-IV) was unknown. In forced degradation study, the drug is degraded into four degradation products under oxidation and photolytic conditions. Two impurities (Imp-III and -IV) were concurred with process related impurities whereas Imp-V and -VI were identified as new degradation impurities. Based on LC-ESI/MS n study, the chemical structures of new impurities were presumed as 1-[(2E)-3-(4-methylphenyl)-3-{6-[(1E)-3-oxobut-1-en-1-yl]pyridin-2-yl}prop-2-en-1-yl]pyrrolidin-1-ium-1-olate (Imp-IV), 1-{[3-(4-methylphenyl)-3-{6-[(1E)-3-oxobut-1-en-1-yl]pyridin-2-yl}oxiran-2-yl]methyl}pyrrolidin-1-ium-1-olate (Imp-V) and 2-[2-(4-methylphenyl)-3-[(1-oxidopyrrolidin-1-ium-1-yl)methyl]oxiran-2-yl]-6-[(1E)-3-oxobut-1-en-1-yl]pyridin-1-ium-1-olate (Imp-VI), and confirmed by their synthesis followed by spectroscopic analysis, IR, NMR ( 1 H, 13 C) and mass. An efficient and selective high-performance liquid chromatography method has been developed and resolved well the drug related substances on a Phenomenex Gemini C-18 (250×4.6mm, particle size 5μm) column. The mobile phase was composed of sodium dihydrogen phosphate (10mM) and methanol, temperature at 25°C, and a PDA detector set at 254nm used for detection. The method was validated with respect to specificity, linearity, precision, accuracy, and sensitivity and satisfactory results were achieved. Identification, synthesis, characterization of impurities and method validation were first reported in this paper. Copyright © 2016 Elsevier B.V. All rights reserved.

Multi-channel transport experiments at Alcator C-Mod and comparison with gyrokinetic simulations

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

White, A. E.; Howard, N. T.; Greenwald, M.

2013-05-15

Multi-channel transport experiments have been conducted in auxiliary heated (Ion Cyclotron Range of Frequencies) L-mode plasmas at Alcator C-Mod [Marmar and Alcator C-Mod Group, Fusion Sci. Technol. 51(3), 3261 (2007)]. These plasmas provide good diagnostic coverage for measurements of kinetic profiles, impurity transport, and turbulence (electron temperature and density fluctuations). In the experiments, a steady sawtoothing L-mode plasma with 1.2 MW of on-axis RF heating is established and density is scanned by 20%. Measured rotation profiles change from peaked to hollow in shape as density is increased, but electron density and impurity profiles remain peaked. Ion or electron heat fluxesmore » from the two plasmas are the same. The experimental results are compared directly to nonlinear gyrokinetic theory using synthetic diagnostics and the code GYRO [Candy and Waltz, J. Comput. Phys. 186, 545 (2003)]. We find good agreement with experimental ion heat flux, impurity particle transport, and trends in the fluctuation level ratio (T(tilde sign){sub e}/T{sub e})/(ñ{sub e}/n{sub e}), but underprediction of electron heat flux. We find that changes in momentum transport (rotation profiles changing from peaked to hollow) do not correlate with changes in particle transport, and also do not correlate with changes in linear mode dominance, e.g., Ion Temperature Gradient versus Trapped Electron Mode. The new C-Mod results suggest that the drives for momentum transport differ from drives for heat and particle transport. The experimental results are inconsistent with present quasilinear models, and the strong sensitivity of core rotation to density remains unexplained.« less

Influence of radiative processes on the ignition of deuterium–tritium plasma containing inactive impurities

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

Gus’kov, S. Yu., E-mail: guskov@sci.lebedev.ru; Sherman, V. E.

2016-08-15

The degree of influence of radiative processes on the ignition of deuterium–tritium (DT) plasma has been theoretically studied as dependent on the content of inactive impurities in plasma. The analytic criterion of plasma ignition in inertial confinement fusion (ICF) targets is modified taking into account the absorption of intrinsic radiation from plasma in the ignition region. The influence of radiative processes on the DT plasma ignition has been analytically and numerically studied for plasma that contains a significant fraction of inactive impurities either as a result of DT fuel mixing with ICF target ablator material or as a result ofmore » using light metal DT-hydrides as solid noncryogenic fuel. It has been shown that the effect of the absorption of intrinsic radiation leads to lower impurity-induced increase in the ignition energy as compared to that calculated in the approximation of optically transparent ignition region.« less

Impact of Pharmaceutical Impurities in Ecstasy Tablets: Gas Chromatography-Mass Spectrometry Study

PubMed Central

Jalali, Amir; Hatamie, Amir; Saferpour, Tahere; Khajeamiri, Alireza; Safa, Tahere; Buazar, Foad

2016-01-01

In this study, a simple and reliable method by gas chromatograph–mass spectrometry (GC–MS) was developed for the fast and regular identification of 3, 4-MDMA impurities in ecstasy tablets. In so doing, 8 samples of impurities were extracted by diethyl ether under alkaline condition and then analyzed by GC–MS. The results revealed high MDMA levels ranging from 37.6% to 57.7%. The GC-MS method showed that unambiguous identification can be achieved for MDMA from 3, 4-methylenedioxyamphetamine (MDA), Amphetamine (AM), methamphetamine (MA) and ketamine (Keta) compounds, respectively. The experimental results indicated the acceptable time window without interfering peaks. It is found that GC-MS was provided a suitable and rapid identification approach for MDMA (Ecstacy) tablets, particularly in the Forensic labs. Consequently, the intense MDMA levels would support the police to develop a simple quantification of impurity in Ecstasy tablets. PMID:27610162

Three new extreme ultraviolet spectrometers on NSTX-U for impurity monitoring

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

Weller, M. E., E-mail: weller4@llnl.gov; Beiersdorfer, P.; Soukhanovskii, V. A.

2016-11-15

Three extreme ultraviolet (EUV) spectrometers have been mounted on the National Spherical Torus Experiment–Upgrade (NSTX-U). All three are flat-field grazing-incidence spectrometers and are dubbed X-ray and Extreme Ultraviolet Spectrometer (XEUS, 8–70 Å), Long-Wavelength Extreme Ultraviolet Spectrometer (LoWEUS, 190–440 Å), and Metal Monitor and Lithium Spectrometer Assembly (MonaLisa, 50–220 Å). XEUS and LoWEUS were previously implemented on NSTX to monitor impurities from low- to high-Z sources and to study impurity transport while MonaLisa is new and provides the system increased spectral coverage. The spectrometers will also be a critical diagnostic on the planned laser blow-off system for NSTX-U, which will bemore » used for impurity edge and core ion transport studies, edge-transport code development, and benchmarking atomic physics codes.« less

Effect of Reduced Flux Iron Ore Pellets on Removal of Impurities from Pig Iron During Induction Melting: A New Phenomenon

NASA Astrophysics Data System (ADS)

Dishwar, Raj Kumar; Agrawal, Shavi; Mandal, A. K.; Mahobia, G. S.; Sinha, O. P.

2018-06-01

The present work represents a comparative study of impurity removal (sulfur, phosphorus, and carbon) from pig iron melt by the addition of lime powder and reduced fluxed iron ore pellets separately in a 5-kg-capacity induction melting furnace. Two types of reduced flux pellets (80% and 50%) of similar basicity ( 3.06) were charged separately into the pool to obtain the different oxidizing atmospheres of the bath. Results showed that the rate of impurity removal increases up to 6 min of exposure time and decreases afterward. Only lime powder charging, sulfur ( 77%), and a small fraction of carbon were removed from pig iron. Phosphorous ( 41%), sulfur ( 53%), and carbon ( 96%) were removed simultaneously when 80% reduced fluxed pellets were used. The present study indicates that the optimum removal of impurities is possible by charging 80% reduced flux iron ore pellets from the pig iron melt.

Electronic and optical properties of MoSe2 monolayer in the presence of Nb impurity: A first principle study

NASA Astrophysics Data System (ADS)

Kumar, Sanjeev; Sharma, Munish; Ahluwalia, P. K.

2018-04-01

The study of electronic and optical properties of Molybdenum diselenide monolayer (1H-MoSe2) in the presence of Niobium impurity (Nb), has been calculated and compared with available experimental and other calculated results in the literature. The electronic and optical properties of this system are investigated in the two cases.i) when MoS2 monolayer is doped suitably with Nb ii) when Nb is added (intercalated in the interstitial sites) suitably. The presence of even 2.08% Nb as an impurity reflects strong bonding with the host and results in semiconducting to metallic transition, which is also reflected in the overlap of σ valence band and п plasmon band in EELS. Thus, Molybdenum diselenide monolayer in the presence of Nb impurity appears to be a potential a candidate for applications in electrical and optical devices.

Quantum simulation in strongly correlated optical lattices

NASA Astrophysics Data System (ADS)

Mckay, David C.

My work on the 87Rb apparatus focuses on three main topics: simulating the Bose-Hubbard (BH) model out of equilibrium, developing thermometry probes, and developing impurity probes using a 3D spin-dependent lattice. Theoretical techniques (e.g., QMC) are adept at describing the equilibrium properties of the BH model, but the dynamics are unknown --- simulation is able to bridge this gap. We perform two experiments to simulate the BH model out of equilibrium. In the first experiment, published in Ref. [1], we measure the decay rate of the center-of-mass velocity for a Bose-Einstein condensate trapped in a cubic lattice. We explore this dissipation for different Bose-Hubbard parameters (corresponding to different lattice depths) and temperatures. We observe a decay rate that asymptotes to a finite value at zero temperature, which we interpret as evidence of intrinsic decay due to quantum tunneling of phase slips. The decay rate exponentially increases with temperature, which is consistent with a cross-over from quantum tunneling to thermal activation. While phase slips are a well-known dissipation mechanism in superconductors, numerous effects prevent unambiguous detection of quantum phase slips. Therefore, our measurement is among the strongest evidence for quantum tunneling of phase slips. In a second experiment, published in Ref. [2] with theory collaborators at Cornell University, we investigate condensate fraction evolution during fast (i.e., millisecond) ramps of the lattice potential depth. These ramps simulate the BH model with time-dependent parameters. We determine that interactions lead to significant condensate fraction redistribution during these ramps, in agreement with mean-field calculations. This result clarifies adiabatic timescales for the lattice gas and strongly constrains bandmapping as an equilibrium probe. Another part of this thesis work involves developing thermometry techniques for the lattice gas. These techniques are important because the ability to measure temperature is required for quantum simulation and to evaluate in-lattice cooling schemes. In work published in Ref. [3], we explore measuring temperature by directly fitting the quasimomentum distribution of a thermal lattice gas. We attempt to obtain quasimomentum distributions by bandmapping, a process in which the lattice depth is reduced slowly compared to the bandgap but fast with respect to all other timescales. We find that these temperature measurements fail when the thermal energy is comparable to the bandwidth of the lattice. This failure results from two main causes. First, the quasimomentum distribution is an insensitive probe at high temperatures because the band is occupied (i.e., additional thermal energy cannot be accommodated in the kinetic energy degrees of freedom). Second, the bandmapping process does not produce accurate quasimomentum distributions because of smoothing at the Brillouin zone edge. We determine that measuring temperature using the in-situ width overcomes these issues. The in-situ width does not asymptote to a finite value as temperature increases, and the in-situ width can be measured directly without using a mapping procedure. In a second experiment, we investigate using condensate fraction (obtained from the time-of-flight momentum distribution) as an indirect means to measure temperature in the superfluid regime of the BH model. Since no standard fitting procedure exists for the lattice time-of-flight distributions, we define and test a procedure as part of this work. We measure condensate fraction for a range of lattice depths varying from deep in the superfluid regime to lattice depths proximate to the Mott-insulator transition. We also vary the entropy per particle, which is measured in the harmonic trap before adiabatically loading into the lattice. As expected, the condensate fraction increases as entropy decreases, and the condensate fraction decreases at high lattice depths (due to quantum depletion). We compare our experimental results to condensate fraction predicted by the non-interacting, Hartree-Fock-Bogoliubov-Popov, and site-decoupled-mean-field theories. Theory and experiment disagree, which motivates several future extensions to this work, including calculating condensate fraction (and testing our fit procedure) using quantum Monte Carlo numerics, and experimentally and theoretically investigating the dynamics of the lattice load process (for the finite-temperature strongly correlated regime). Finally, we develop impurity probes for the Bose-Hubbard model by employing a spin-dependent lattice. A primary accomplishment of this thesis work was to develop the first 3D spin-dependent lattice in the strongly correlated regime (published in Ref. [4]). The spin-dependent lattice depth is proportional to |gFmF|, enabling the creation of mixtures of atoms trapped in the lattice (nonzero mF) co-trapped with atoms that do not experience the lattice (mF≠ 0). We use the non-lattice atoms as an impurity probe. We investigate using the impurity to probe the lattice temperature, and we determine that thermalization between the impurity and lattice gas is suppressed for larger lattice depths. Using a comparison to a Fermi's golden rule calculation of the collisional energy exchange rate, we determine that this effect is consistent with suppression of energy-exchanging collisions by a mismatch between the impurity and lattice gas dispersion. While this result invalidates the concept of an impurity thermometer, it paves the way for a unique cooling scheme that relies on inter-species thermal isolation. We also explore impurity transport through the lattice gas. In other preliminary measurements, we also identify the decay rate of the center-of-mass motion as a prospective impurity probe.

A validated ultra high-pressure liquid chromatography method for separation of candesartan cilexetil impurities and its degradents in drug product

PubMed Central

Kumar, Namala Durga Atchuta; Babu, K. Sudhakar; Gosada, Ullas; Sharma, Nitish

2012-01-01

Introduction: A selective, specific, and sensitive “Ultra High-Pressure Liquid Chromatography” (UPLC) method was developed for determination of candesartan cilexetil impurities as well asits degradent in tablet formulation. Materials and Methods: The chromatographic separation was performed on Waters Acquity UPLC system and BEH Shield RP18 column using gradient elution of mobile phase A and B. 0.01 M phosphate buffer adjusted pH 3.0 with Orthophosphoric acid was used as mobile phase A and 95% acetonitrile with 5% Milli Q Water was used as mobile phase B. Ultraviolet (UV) detection was performed at 254 nm and 210 nm, where (CDS-6), (CDS-5), (CDS-7), (Ethyl Candesartan), (Desethyl CCX), (N-Ethyl), (CCX-1), (1 N Ethyl Oxo CCX), (2 N Ethyl Oxo CCX), (2 N Ethyl) and any unknown impurity were monitored at 254 nm wavelength, and two process-related impurities, trityl alcohol and MTE impurity, were estimated at 210 nm. Candesartan cilexetil andimpurities were chromatographed with a total run time of 20 min. Results: Calibration showed that the response of impurity was a linear function of concentration over the range limit of quantification to 2 μg/mL (r2≥0.999) and the method was validated over this range for precision, intermediate precision, accuracy, linearity, and specificity. For the precision study, percentage relative standard deviation of each impurity was <15% (n=6). Conclusion: The method was found to be precise, accurate, linear, and specific. The proposed method was successfully employed for estimation of candesartan cilexetil impurities in pharmaceutical preparations. PMID:23781475

Influence of the ordering of impurities on the appearance of an energy gap and on the electrical conductance of graphene.

PubMed

Repetsky, S P; Vyshyvana, I G; Kruchinin, S P; Bellucci, Stefano

2018-06-14

In the one-band model of strong coupling, the influence of substitutional impurity atoms on the energy spectrum and electrical conductance of graphene is studied. It is established that the ordering of substitutional impurity atoms on nodes of the crystal lattice causes the appearance of a gap in the energy spectrum of graphene with width η|δ| centered at the point yδ, where η is the parameter of ordering, δ is the difference of the scattering potentials of impurity atoms and carbon atoms, and y is the impurity concentration. The maximum value of the parameter of ordering is [Formula: see text]. For the complete ordering of impurity atoms, the energy gap width equals [Formula: see text]. If the Fermi level falls in the region of the mentioned gap, then the electrical conductance [Formula: see text] at the ordering of graphene, i.e., the metal-dielectric transition arises. If the Fermi level is located outside the gap, then the electrical conductance increases with the parameter of order η by the relation [Formula: see text]. At the concentration [Formula: see text], as the ordering of impurity atoms η →1, the electrical conductance of graphene [Formula: see text], i.e., the transition of graphene in the state of ideal electrical conductance arises.

Solutal Convection Around Growing Protein Crystal and Diffusional Purification in Space

NASA Technical Reports Server (NTRS)

Lee, Chun P.; Chernov, Alexander A.

2004-01-01

At least some protein crystals were found to preferentially trap microheterogeneous impurities. The latter are, for example, dimmer molecules of the crystallizing proteines (e.g. ferritin, lysozyme), or the regular molecules on which surfaces small molecules or ions are adsorbed (e.g. acetilated lysozyme) and modi@ molecular charge. Impurities may induce lattice defects and deteriorate structural resolution. Distribution of impurities between mother solution and gorwing crystal is defined by two interrelated distribution coefficients: kappa = rho(sup c, sub 2) and K = (rho(sup c, sub 2)/rho(sup c, sub 1)/rho(sub 2)/rho(sub 1). Here, rho(sub 2), rho(sub 1) and rho(sup c, sub 2) are densities of impurity (2) and regular protein (1) in solution at the growing interface and within the crystal ("c"). For the microheterogeneous impurities studied, K approx. = 2 - 4, so that kappa approx. - 10(exp 2) - 10(exp 3), since K = kappa (rho(sub 1)/rho(sup c, sub 1) and protein solubility ratio rho(sub 1)/rho(sub=p c, sub 2) much less than 1. Therefore, a crystal growing in absence of convection purifies mother solution around itself, grows cleaner and, probably, more perfect. If convection is present, the solution flow permanently brings new impurities to the crystal. This work theoretically addressed two subjects: 1) onset of convection, 2) distribution of impurities.

Self-consistent gyrokinetic modeling of neoclassical and turbulent impurity transport

NASA Astrophysics Data System (ADS)

Estève, D.; Sarazin, Y.; Garbet, X.; Grandgirard, V.; Breton, S.; Donnel, P.; Asahi, Y.; Bourdelle, C.; Dif-Pradalier, G.; Ehrlacher, C.; Emeriau, C.; Ghendrih, Ph.; Gillot, C.; Latu, G.; Passeron, C.

2018-03-01

Trace impurity transport is studied with the flux-driven gyrokinetic GYSELA code (Grandgirard et al 2016 Comput. Phys. Commun. 207 35). A reduced and linearized multi-species collision operator has been recently implemented, so that both neoclassical and turbulent transport channels can be treated self-consistently on an equal footing. In the Pfirsch-Schlüter regime that is probably relevant for tungsten, the standard expression for the neoclassical impurity flux is shown to be recovered from gyrokinetics with the employed collision operator. Purely neoclassical simulations of deuterium plasma with trace impurities of helium, carbon and tungsten lead to impurity diffusion coefficients, inward pinch velocities due to density peaking, and thermo-diffusion terms which quantitatively agree with neoclassical predictions and NEO simulations (Belli et al 2012 Plasma Phys. Control. Fusion 54 015015). The thermal screening factor appears to be less than predicted analytically in the Pfirsch-Schlüter regime, which can be detrimental to fusion performance. Finally, self-consistent nonlinear simulations have revealed that the tungsten impurity flux is not the sum of turbulent and neoclassical fluxes computed separately, as is usually assumed. The synergy partly results from the turbulence-driven in-out poloidal asymmetry of tungsten density. This result suggests the need for self-consistent simulations of impurity transport, i.e. including both turbulence and neoclassical physics, in view of quantitative predictions for ITER.

Carbon impurities behavior and its impact on ion thermal confinement in high-ion-temperature deuterium discharges on the Large Helical Device

NASA Astrophysics Data System (ADS)

Mukai, K.; Nagaoka, K.; Takahashi, H.; Yokoyama, M.; Murakami, S.; Nakano, H.; Ida, K.; Yoshinuma, M.; Seki, R.; Kamio, S.; Fujiwara, Y.; Oishi, T.; Goto, M.; Morita, S.; Morisaki, T.; Osakabe, M.; LHD Experiment Group1, the

2018-07-01

The behavior of carbon impurities in deuterium plasmas and its impact on thermal confinement were investigated in comparison with hydrogen plasmas in the Large Helical Device (LHD). Deuterium plasma experiments have been started in the LHD and high-ion-temperature plasmas with central ion temperature (T i) of 10 keV were successfully obtained. The thermal confinement improvement could be sustained for a longer time compared with hydrogen plasmas. An isotope effect was observed in the time evolution of the carbon density profiles. A transiently peaked profile was observed in the deuterium plasmas due to the smaller carbon convection velocity and diffusivity in the deuterium plasmas compared with the hydrogen plasmas. The peaked carbon density profile was strongly correlated to the ion thermal confinement improvement. The peaking of the carbon density profile will be one of the clues to clarify the unexplained mechanisms for the formations of ion internal transport barrier and impurity hole on LHD. These results could also lead to a better understanding of the isotope effect in the thermal confinement in torus plasma.

In-gap quasiparticle excitations induced by non-magnetic Cu impurities in Na(Fe0.96Co0.03Cu0.01)As revealed by scanning tunnelling spectroscopy

PubMed Central

Yang, Huan; Wang, Zhenyu; Fang, Delong; Deng, Qiang; Wang, Qiang-Hua; Xiang, Yuan-Yuan; Yang, Yang; Wen, Hai-Hu

2013-01-01

The origin of superconductivity in the iron pnictides remains unclear. One suggestion is that superconductivity in these materials has a magnetic origin, which would imply a sign-reversal s± pairing symmetry. Another suggests it is the result of orbital fluctuations, which would imply a sign-equal s++ pairing symmetry. There is no consensus yet which of these two distinct and contrasting pairing symmetries is the right one in iron pnictide superconductors. Here we explore the nature of the pairing symmetry in the superconducting state of Na(Fe0.97−xCo0.03Cux)As by probing the effect of scattering of Cooper pairs by non-magnetic Cu impurities. Using scanning tunnelling spectroscopy, we identify the in-gap quasiparticle states induced by the Cu impurities, showing signatures of Cooper pair breaking by these non-magnetic impurities–a process that is only consistent with s± pairing. This experiment provides strong evidence for the s± pairing. PMID:24248097

The effect of shallow vs. deep level doping on the performance of thermoelectric materials

NASA Astrophysics Data System (ADS)

Song, Qichen; Zhou, Jiawei; Meroueh, Laureen; Broido, David; Ren, Zhifeng; Chen, Gang

2016-12-01

It is well known that the efficiency of a good thermoelectric material should be optimized with respect to doping concentration. However, much less attention has been paid to the optimization of the dopant's energy level. Thermoelectric materials doped with shallow levels may experience a dramatic reduction in their figures of merit at high temperatures due to the excitation of minority carriers that reduces the Seebeck coefficient and increases bipolar heat conduction. Doping with deep level impurities can delay the excitation of minority carriers as it requires a higher temperature to ionize all dopants. We find through modeling that, depending on the material type and temperature range of operation, different impurity levels (shallow or deep) will be desired to optimize the efficiency of a thermoelectric material. For different materials, we further clarify where the most preferable position of the impurity level within the bandgap falls. Our research provides insight on why different dopants often affect thermoelectric transport properties differently and directions in searching for the most appropriate dopants for a thermoelectric material in order to maximize the device efficiency.

Impurity-assisted terahertz photoluminescence in quantum wells under conditions of interband stimulated emission

NASA Astrophysics Data System (ADS)

Makhov, I. S.; Panevin, V. Yu; Firsov, D. A.; Vorobjev, L. E.; Sofronov, A. N.; Vinnichenko, M. Ya; Maleev, N. A.; Vasil'ev, A. P.

2018-03-01

Terahertz and near-infrared photoluminescence under conditions of interband stimulated emission are studied in n-GaAs/AlGaAs quantum well laser structure. The observed terahertz emission is related to the optical transitions of nonequilibrium electrons from the first electron subband and excited donor states to donor ground states in quantum wells. The opportunity to increase the intensity of impurity-assisted terahertz emission due to interband stimulated emission with the participation of impurity centres is demonstrated.

An investigation of plastic fracture in aluminum alloys

NASA Technical Reports Server (NTRS)

Low, J. R., Jr.; Vanstone, R. H.; Merchant, R. H.

1972-01-01

The brittle fracture of many high strength alloys such as steel, titanium, and aluminum was shown to occur by a process called plastic fracture. According to this process microscopic voids form at impurity particles, then grow and coalesce to cause the final rupture. To further understand the role of impurities, four aluminum alloys were investigated: 2024-T851, 2124-T851, 7075-T7351 and 7079-T651. Fractography, quantitative metallography, and microprobe studies assessed the roles of various impurity particles relative to these alloys.

Effect of Macroscopic Impurities on Resistive Measurements in Three Dimensions

NASA Astrophysics Data System (ADS)

Koon, Daniel W.

1997-03-01

The authors extend their study of the effect of macroscopic impurities on resistive measurements to include specimens of finite thickness. The effect of such impurities is calculated for a rectangular parallelepiped with two current and two voltage contacts on the corners of one of its faces. The weighting function(D. W. Koon and C. J. Knickerbocker, Rev. Sci. Instrum. 63, 207 (1992).) displays singularities near these contacts, but these are shown to vanish in the two-dimensional limit, in agreement with previous results.

High temperature corrosion of a nickel base alloy by helium impurities

NASA Astrophysics Data System (ADS)

Rouillard, F.; Cabet, C.; Wolski, K.; Terlain, A.; Tabarant, M.; Pijolat, M.; Valdivieso, F.

2007-05-01

High temperature corrosion properties of Haynes 230 were investigated in a purposely-designed facility under a typical very high temperature reactor (VHTR) impure helium medium. The study was focused on the surface oxide scale formation and its stability at about 1223 K. The alloy developed a Mn/Cr rich oxide layer on its surface under impure helium at 1173 K. Nevertheless, a deleterious reaction destructing the chromium oxide was evidenced above a critical temperature, TA. Reagents and products of this last reaction were investigated.

Magnetic field effect on pentacene-doped sexithiophene diodes

NASA Astrophysics Data System (ADS)

Pham, Song-Toan; Fayolle, Marine; Ohto, Tatsuhiko; Tada, Hirokazu

2017-11-01

We studied the effect of impurities on the magnetoresistance of sexithiophene-based diodes using impedance spectroscopy. The impurities were introduced by doping pentacene molecules into a sexithiophene film through a co-evaporation process. The pentacene molecules act as charge-scattering centers, which trigger the negative magnetoresistance of the device. This makes it possible to tune the value of magnetoresistance from positive to negative by increasing the applied voltage. The beneficial properties induced by impurities suggest a potential route to integrate additional functions into organic devices.

Habit modification of potassium acid phthalate (KAP) single crystals by impurities

NASA Astrophysics Data System (ADS)

Murugakoothan, P.; Mohan Kumar, R.; Ushasree, P. M.; Jayavel, R.; Dhanasekaran, R.; Ramasamy, P.

1999-12-01

Nonlinear optical materials potassium dihydrogen phosphate (KDP), urea and L-arginine phosphate (LAP)-doped KAP crystals were grown by the slow cooling method. The LAP-doped crystals show pronounced habit modification compared to KDP and urea doping. The effect of these impurities on growth kinetics, surface morphology, habit modification, structure, optical and mechanical properties have been studied. Among the three impurities, urea doping yields high mechanical stability and optical transmission and for KDP and LAP doping there is a decrease in optical transmission.

Study of structure defect interactions in aluminum by the acoustic method. [internal friction in pure aluminum

NASA Technical Reports Server (NTRS)

Nicolaescu, I. I.

1974-01-01

Using echo pulse and resonance rod methods, internal friction in pure aluminum was studied as a function of frequency, hardening temperature, time (internal friction relaxation) and impurity content. These studies led to the conclusion that internal friction in these materials depends strongly on dislocation structure and on elastic interactions between structure defects. It was found experimentally that internal friction relaxation depends on the cooling rate and on the impurity content. Some parameters of the dislocation structure and of the diffusion process were determined. It is shown that the dislocated dependence of internal friction can be used as a method of nondestructive testing of the impurity content of high-purity materials.

Effects of impurities on crystal growth in fructose crystallization

NASA Astrophysics Data System (ADS)

Chu, Y. D.; Shiau, L. D.; Berglund, K. A.

1989-10-01

The influence of impurities on the crystallization of anhydrous fructose from aqueous solution was studied. The growth kinetics of fructose crystals in the fructose-water-glucose and fructose-water-difructose dianhydrides systems were investigated using photomicroscopic contact nucleation techniques. Glucose is the major impurity likely to be present in fructose syrup formed during corn wet milling, while several difructose dianhydrides are formed in situ under crystallization conditions and have been proposed as a cause in the decrease of overall yields. Both sets of impurities were found to cause inhibition of crystal growth, but the mechanisms responsible in each case are different. It was found that the presence of glucose increases the solubility of fructose in water and thus lowers the supersaturation of the solution. This is probably the main effect responsible for the decrease of crystal growth. Since the molecular structures of difructose dianhydrides are similar to that of fructose, they are probably "tailor-made" impurities. The decrease of crystal growth is probably caused by the incorporation of these impurities into or adsorption to the crystal surface which would accept fructose molecules in the orientation that existed in the difructose dianhydride.

Identification of process related trace level impurities in the actinide decorporation agent 3,4,3-LI(1,2-HOPO): Nozzle–skimmer fragmentation via ESI LC–QTOFMS

DOE PAGES

Panyala, Nagender R.; Sturzbecher-Hoehne, Manuel; Abergel, Rebecca J.

2014-08-12

We report that 3,4,3-LI(1,2-HOPO) is a chelating ligand and decorporation agent that can remove radioactive lanthanides and actinides from the body. Identification of trace impurities in drug samples is gaining much interest due to their significant influence on drug activity. In this study, trace impurities were detected in manufactured lots of 3,4,3-LI(1,2-HOPO) by a developed method of Liquid Chromatography coupled with photo-diode array UV detection and Electrospray Ionization-Quadrupole Time of Flight Mass spectrometry (LC-QTOFMS), via induced-in-source or collision-induced mass fragmentation (Nozzle-Skimmer Fragmentation). Molecular ions were fragmented within the nozzle-skimmer region of electrospray ionization (ESI) mass spectrometer equipped with a Timemore » of Flight detector. Eight major (detected at levels higher than a 0.1% threshold) and seven minor trace impurities were identified. The respective structures of these impurities were elucidated via analysis of the generated fragment ions using mass fragmentation and elemental composition software. Proposed structures of impurities were further confirmed via isotopic modeling.« less

Electronic structure of vitamin B12 within the framework of the Haldane-Anderson impurity model

NASA Astrophysics Data System (ADS)

Kandemir, Zafer; Mayda, Selma; Bulut, Nejat

2015-03-01

We study the electronic structure of vitamin B12 (cyanocobalamine C63H88CoN14O14P) by using the framework of the multi-orbital single-impurity Haldane-Anderson model of a transition-metal impurity in a semiconductor host. Here, our purpose is to understand the many-body effects originating from the transition-metal impurity. In this approach, the cobalt 3 d orbitals are treated as the impurity states placed in a semiconductor host which consists of the rest of the molecule. The parameters of the resulting effective Haldane-Anderson model are obtained within the Hartree-Fock approximation for the electronic structure of the molecule. The quantum Monte Carlo technique is then used to calculate the one-electron and magnetic correlation functions of this effective Haldane-Anderson model for vitamin B12. We find that new states form inside the semiconductor gap due to the on-site Coulomb interaction at the impurity 3 d orbitals and that these states become the highest occupied molecular orbitals. In addition, we present results on the charge distribution and spin correlations around the Co atom. We compare the results of this approach with those obtained by the density-functional theory calculations.

Universal scaling for the quantum Ising chain with a classical impurity

NASA Astrophysics Data System (ADS)

Apollaro, Tony J. G.; Francica, Gianluca; Giuliano, Domenico; Falcone, Giovanni; Palma, G. Massimo; Plastina, Francesco

2017-10-01

We study finite-size scaling for the magnetic observables of an impurity residing at the end point of an open quantum Ising chain with transverse magnetic field, realized by locally rescaling the field by a factor μ ≠1 . In the homogeneous chain limit at μ =1 , we find the expected finite-size scaling for the longitudinal impurity magnetization, with no specific scaling for the transverse magnetization. At variance, in the classical impurity limit μ =0 , we recover finite scaling for the longitudinal magnetization, while the transverse one basically does not scale. We provide both analytic approximate expressions for the magnetization and the susceptibility as well as numerical evidences for the scaling behavior. At intermediate values of μ , finite-size scaling is violated, and we provide a possible explanation of this result in terms of the appearance of a second, impurity-related length scale. Finally, by going along the standard quantum-to-classical mapping between statistical models, we derive the classical counterpart of the quantum Ising chain with an end-point impurity as a classical Ising model on a square lattice wrapped on a half-infinite cylinder, with the links along the first circle modified as a function of μ .

Synthesis of compounds related to the anti-migraine drug eletriptan hydrobromide.

PubMed

Madasu, Suri Babu; Vekariya, Nagaji Ambabhai; Kiran, M N V D Hari; Gupta, Badarinadh; Islam, Aminul; Douglas, Paul S; Babu, Korupolu Raghu

2012-01-01

Eletriptan hydrobromide (1) is a selective serotonin (5-HT(1)) agonist, used for the acute treatment of the headache phase of migraine attacks. During the manufacture of eletriptan hydrobromide the formation of various impurities were observed and identified by LC-MS. To control the formation of these impurities during the preparation of active pharmaceutical ingredients, the structure of the impurities must be known. Major impurities of the eletriptan hydrobromide synthesis were prepared and characterized by using various spectroscopic techniques, i.e., mass spectroscopy, FTIR , (1)H NMR, (13)C NMR/DEPT, and further confirmed by co-injection in HPLC. The present study will be of great help in the synthesis of highly pure eletriptan hydrobromide related compounds.

Synthesis of compounds related to the anti-migraine drug eletriptan hydrobromide

PubMed Central

Madasu, Suri Babu; Kiran, M N V D Hari; Gupta, Badarinadh; Islam, Aminul; Douglas, Paul S; Babu, Korupolu Raghu

2012-01-01

Summary Eletriptan hydrobromide (1) is a selective serotonin (5-HT1) agonist, used for the acute treatment of the headache phase of migraine attacks. During the manufacture of eletriptan hydrobromide the formation of various impurities were observed and identified by LC–MS. To control the formation of these impurities during the preparation of active pharmaceutical ingredients, the structure of the impurities must be known. Major impurities of the eletriptan hydrobromide synthesis were prepared and characterized by using various spectroscopic techniques, i.e., mass spectroscopy, FTIR , 1H NMR, 13C NMR/DEPT, and further confirmed by co-injection in HPLC. The present study will be of great help in the synthesis of highly pure eletriptan hydrobromide related compounds. PMID:23019477

The Effects of Hydrogen-Like Impurity and Temperature on State Energies and Transition Frequency of Strong-Coupling Bound Polaron in an Asymmetric Gaussian Potential Quantum Well

NASA Astrophysics Data System (ADS)

Xiao, Jing-lin

2018-02-01

In the present work, we study the ground state energy, the first excited state energy and the transition frequency (TF) between the two states of the strong-coupling impurity bound polaron in an asymmetric Gaussian potential quantum well (AGPQW) by using the variational method of the Pekar type. By employing quantum statistics theory, the temperature effect on the state energies (SEs) and the TF are also calculated with a hydrogen-like impurity at the coordinate origin of the AGPQW. According to the obtained results, we found that the SEs and the TF are increasing functions of the temperature, whereas they are decreasing ones of the Coulombic impurity potential.

Diffusive Propagation of Exciton-Polaritons through Thin Crystal Slabs

PubMed Central

Zaitsev, D. A.; Il’ynskaya, N. D.; Koudinov, A. V.; Poletaev, N. K.; Nikitina, E. V.; Egorov, A. Yu.; Kavokin, A. V.; Seisyan, R. P.

2015-01-01

If light beam propagates through matter containing point impurity centers, the amount of energy absorbed by the media is expected to be either independent of the impurity concentration N or proportional to N, corresponding to the intrinsic absorption or impurity absorption, respectively. Comparative studies of the resonant transmission of light in the vicinity of exciton resonances measured for 15 few-micron GaAs crystal slabs with different values of N, reveal a surprising tendency. While N spans almost five decimal orders of magnitude, the normalized spectrally-integrated absorption of light scales with the impurity concentration as N1/6. We show analytically that this dependence is a signature of the diffusive mechanism of propagation of exciton-polaritons in a semiconductor. PMID:26088555

Experimental pathways to understand and avoid high-Z impurity contamination from ICRF heating in tokamaks

NASA Astrophysics Data System (ADS)

Reinke, Matthew

2016-10-01

Recent results from Alcator C-Mod and JET demonstrate progress in understanding and mitigating core high-Z impurity contamination linked to ICRF heating in tokamaks with high-Z PFCs. Theory has identified two likely mechanisms: impurity sources due to sputtering enhanced by RF-rectified sheaths and greater cross-field SOL transport due to ExB convective cells. New experiments on Alcator C-Mod and JET demonstrate convective cell transport is likely a sub-dominant effect, despite directly observing ExB flows from rectified RF fields on C-Mod. Trace N2 introduced in the far SOL on field lines connected to and well away from an active ICRF antenna result in similar levels of core nitrogen, indicating local RF-driven transport is weak. This suggests the core high-Z density, nZ,core, is determined by sheath-induced sputtering and RF-independent SOL transport, allowing further reductions through antenna design. ICRF heating on C-Mod uses a unique, field aligned (FAA) and a pair of conventional, toroidally aligned (TAA) antennas. The FAA is designed to reduce rectified voltages relative to the TAA, and the impact of sheath-induced sputtering is explored by observing nZ,core while varying the TAA/FAA heating mix. A reduction of approximately 50% in core high-Z content is seen in L-modes when using the FAA and high-Z sources at the antenna limiter are effectively eliminated, indicating the remaining RF-driven source is away from the limiter. A drop in nZ,core may also be realized by locating the RF antenna on the inboard side where SOL transport aids impurity screening. New C-Mod experiments demonstrate up to a factor of 5 reduction in core nitrogen when N2 is injected on the high-field side as compared to low-field side impurity fueling. Varying the magnetic topology helps to elucidate the SOL transport physics responsible, laying a physics basis for inboard RF antenna placement. This work is supported by U.S. DOE Award DE-FC02-99ER54512, using Alcator C-Mod and carried out within the framework of the EUROfusion Consortium and has received funding from Euratom under Grant Agreement No 633053.

Effects of doping impurity and growth orientation on dislocation generation in GaAs crystals grown from the melt: A qualitative finite-element study

NASA Astrophysics Data System (ADS)

Zhu, X. A.; Tsai, C. T.

2000-09-01

Dislocations in gallium arsenide (GaAs) crystals are generated by excessive thermal stresses induced during the crystal growth process. The presence of dislocations has adverse effects on the performance and reliability of the GaAs-based devices. It is well known that dislocation density can be significantly reduced by doping impurity atoms into a GaAs crystal during its growth process. A viscoplastic constitutive equation that couples the microscopic dislocation density with the macroscopic plastic deformation is employed in a crystallographic finite element model for calculating the dislocation density generated in the GaAs crystal during its growth process. The dislocation density is considered as an internal state variable and the drag stress caused by doping impurity is included in this constitutive equation. A GaAs crystal grown by the vertical Bridgman process is adopted as an example to study the influences of doping impurity and growth orientation on dislocation generation. The calculated results show that doping impurity can significantly reduce the dislocation density generated in the crystal. The level of reduction is also influenced by the growth orientation during the crystal growth process.

Robust superconductivity with nodes in the superconducting topological insulator CuxBi2Se3 : Zeeman orbital field and nonmagnetic impurities

NASA Astrophysics Data System (ADS)

Nagai, Yuki

2015-02-01

We study the robustness against nonmagnetic impurities in the topological superconductor with point nodes, focusing on an effective model of CuxBi2Se3 . We find that the topological superconductivity with point nodes is not fragile against nonmagnetic impurities, although the superconductivity with nodes in past studies is usually fragile. Exchanging the role of spin with the one of orbital, and vice versa, we find that in the "dual" space the topological superconductor with point nodes is regarded as the intraorbital spin-singlet s -wave one. From the viewpoint of the dual space, we deduce that the point-node state is not fragile against nonmagnetic impurity, when the orbital imbalance in the normal states is small. Since the spin imbalance is induced by the Zeeman magnetic field, we shall name this key quantity for the impurity effects the Zeeman "orbital" field. The numerical calculations support that the deduction is correct. If the Zeeman orbital field is small, the topological superconductivity is not fragile in dirty materials, even with nodes. Thus, the topological superconductors cannot be simply regarded as one of the conventional unconventional superconductors.

Mass Spectrometric Distinction of In-Source and In-Solution Pyroglutamate and Succinimide in Proteins: A Case Study on rhG-CSF

NASA Astrophysics Data System (ADS)

Kumar, Mukesh; Chatterjee, Amarnath; Khedkar, Anand P.; Kusumanchi, Mutyalasetty; Adhikary, Laxmi

2013-02-01

Formation of cyclic intermediates involving water or ammonia loss is a common occurrence in any reaction involving terminal amines or hydroxyl group containing species. Proteins that have both these functional groups in abundance are no exception, and presence of amino acids such as asparagine, glutamines, aspartic acids, and glutamic acids aid in formation of such intermediates. In the biopharma scenario, such intermediates lead to product- or process-related impurities that might be immunogenic. Mass spectroscopy is a powerful technique that is used to decipher the presence and physicochemical characteristics of such impurities. However, such intermediates can also form in situ during mass spectrometric analysis. We present here the detection of in-source and in-solution formation of succinimide and pyroglutamate in the protein granulocyte colony stimulating factor. We also propose an approach for quick differentiation of such in-situ species from the tangible impurities. We believe that this will not only reduce the time spent in unambiguous identification of succinimide- and/or pyroglutamate-related impurity in bio-pharmaceutics but also provide a platform for similar studies on other impurities that may form due to stabilized intermediates.

Occurrence and Characterization Microstructure of Iron Impurities in Halloysite.

PubMed

Liu, Rong; Yan, Chunjie; Wang, Hongquan; Xiao, Guoqi; Tu, Dong

2015-09-01

The quality of the clays and over all halloysite are mostly associated with minor amounts of ferruginous impurities content, since this element gives an undesirable reddish color to the halloysite mineral. Hence, finding out the modes of occurrence of iron in halloysite is of prime importance in the value addition and optimum utilization of halloysite. In order to analyze the occurrence of iron impurities in halloysite, Transmission Electron Microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were combined with wet chemical analysis methods to study the low-grade halloysite. The results indicated that the mineral phases of iron impurities in the concentrates are mainly composed of amounts of magnetite, goethite and hematite. Two types of occurrences for iron impurities have been found. One is single crystalline mineral consist in the halloysite, which contains three different phases of Goethite FeO(OH) (44.75%), Magnetite Fe3O4 (27.43%) and Hematite Fe2O3 (31.96%). The other is amorphous Fe-Al-Si glial materials. This study is of significance in the theoretical research on the halloysite mineralogy and in the developmental practice of halloysite in coal measures.

Impurity-induced tuning of quantum-well States in spin-dependent resonant tunneling.

PubMed

Kalitsov, Alan; Coho, A; Kioussis, Nicholas; Vedyayev, Anatoly; Chshiev, M; Granovsky, A

2004-07-23

We report exact model calculations of the spin-dependent tunneling in double magnetic tunnel junctions in the presence of impurities in the well. We show that the impurity can tune selectively the spin channels giving rise to a wide variety of interesting and novel transport phenomena. The tunneling magnetoresistance, the spin polarization, and the local current can be dramatically enhanced or suppressed by impurities. The underlying mechanism is the impurity-induced shift of the quantum well states (QWSs), which depends on the impurity potential, impurity position, and the symmetry of the QWS. Copyright 2004 The American Physical Society

Process and system for removing impurities from a gas

DOEpatents

Henningsen, Gunnar; Knowlton, Teddy Merrill; Findlay, John George; Schlather, Jerry Neal; Turk, Brian S

2014-04-15

A fluidized reactor system for removing impurities from a gas and an associated process are provided. The system includes a fluidized absorber for contacting a feed gas with a sorbent stream to reduce the impurity content of the feed gas; a fluidized solids regenerator for contacting an impurity loaded sorbent stream with a regeneration gas to reduce the impurity content of the sorbent stream; a first non-mechanical gas seal forming solids transfer device adapted to receive an impurity loaded sorbent stream from the absorber and transport the impurity loaded sorbent stream to the regenerator at a controllable flow rate in response to an aeration gas; and a second non-mechanical gas seal forming solids transfer device adapted to receive a sorbent stream of reduced impurity content from the regenerator and transfer the sorbent stream of reduced impurity content to the absorber without changing the flow rate of the sorbent stream.

Motion of a Distinguishable Impurity in the Bose Gas: Arrested Expansion Without a Lattice and Impurity Snaking

NASA Astrophysics Data System (ADS)

Robinson, Neil J.; Caux, Jean-Sébastien; Konik, Robert M.

2016-04-01

We consider the real-time dynamics of an initially localized distinguishable impurity injected into the ground state of the Lieb-Liniger model. Focusing on the case where integrability is preserved, we numerically compute the time evolution of the impurity density operator in regimes far from analytically tractable limits. We find that the injected impurity undergoes a stuttering motion as it moves and expands. For an initially stationary impurity, the interaction-driven formation of a quasibound state with a hole in the background gas leads to arrested expansion—a period of quasistationary behavior. When the impurity is injected with a finite center-of-mass momentum, the impurity moves through the background gas in a snaking manner, arising from a quantum Newton's cradlelike scenario where momentum is exchanged back and forth between the impurity and the background gas.

Motion of a distinguishable Impurity in the Bose gas: Arrested expansion without a lattice and impurity snaking

DOE PAGES

Neil J. Robinson; Caux, Jean -Sebastien; Konik, Robert M.

2016-04-07

We consider the real-time dynamics of an initially localized distinguishable impurity injected into the ground state of the Lieb-Liniger model. Focusing on the case where integrability is preserved, we numerically compute the time evolution of the impurity density operator in regimes far from analytically tractable limits. We find that the injected impurity undergoes a stuttering motion as it moves and expands. For an initially stationary impurity, the interaction-driven formation of a quasibound state with a hole in the background gas leads to arrested expansion—a period of quasistationary behavior. In conclusion, when the impurity is injected with a finite center-of-mass momentum,more » the impurity moves through the background gas in a snaking manner, arising from a quantum Newton’s cradlelike scenario where momentum is exchanged back and forth between the impurity and the background gas.« less

Yu-Shiba-Rusinov states of impurities in a triangular lattice of NbSe2 with spin-orbit coupling

NASA Astrophysics Data System (ADS)

Ptok, Andrzej; Głodzik, Szczepan; Domański, Tadeusz

2017-11-01

We study the topography of the spin-polarized bound states of magnetic impurities embedded in a triangular lattice of a superconducting host. Such states have been observed experimentally in 2 H -NbSe2 crystal [G. C. Ménard et al., Nat. Phys. 11, 1013 (2015), 10.1038/nphys3508], and they revealed oscillating particle-hole asymmetry extending to tens of nanometers. Using the Bogoliubov-de Gennes approach, we explore the Yu-Shiba-Rusinov states in the presence of spin-orbit interaction. We also study the bound states of double impurities for several relative positions in a triangular lattice.

Case study to illustrate an approach for detecting contamination and impurities in pesticide formulations.

PubMed

Karasali, Helen; Kasiotis, Konstantinos M; Machera, Kyriaki; Ambrus, Arpad

2014-11-26

Counterfeit pesticides threaten public health, food trade, and the environment. The present work draws attention to the importance of regular monitoring of impurities in formulated pesticide products. General screening revealed the presence of carbaryl as a contaminant in a copper oxychloride formulated product. In this paper, as a case study, a liquid chromatographic diode array-mass spectrometric method developed for general screening of pesticide products and quantitative determination of carbaryl together with its validation is presented. The proposed testing strategy is considered suitable for use as a general approach for testing organic contaminants and impurities in solid pesticide formulations.

Analytical advances in pharmaceutical impurity profiling.

PubMed

Holm, René; Elder, David P

2016-05-25

Impurities will be present in all drug substances and drug products, i.e. nothing is 100% pure if one looks in enough depth. The current regulatory guidance on impurities accepts this, and for drug products with a dose of less than 2g/day identification of impurities is set at 0.1% levels and above (ICH Q3B(R2), 2006). For some impurities, this is a simple undertaking as generally available analytical techniques can address the prevailing analytical challenges; whereas, for others this may be much more challenging requiring more sophisticated analytical approaches. The present review provides an insight into current development of analytical techniques to investigate and quantify impurities in drug substances and drug products providing discussion of progress particular within the field of chromatography to ensure separation of and quantification of those related impurities. Further, a section is devoted to the identification of classical impurities, but in addition, inorganic (metal residues) and solid state impurities are also discussed. Risk control strategies for pharmaceutical impurities aligned with several of the ICH guidelines, are also discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

Supercritical fluid chromatography-photodiode array detection-electrospray ionization mass spectrometry as a framework for impurity fate mapping in the development and manufacture of drug substances.

PubMed

Pirrone, Gregory F; Mathew, Rose M; Makarov, Alexey A; Bernardoni, Frank; Klapars, Artis; Hartman, Robert; Limanto, John; Regalado, Erik L

2018-03-30

Impurity fate and purge studies are critical in order to establish an effective impurity control strategy for approval of the commercial filing application of new medicines. Reversed phase liquid chromatography-diode array-mass spectrometry (RPLC-DAD-MS) has traditionally been the preferred tool for impurity fate mapping. However, separation of some reaction mixtures by LC can be very problematic requiring combination LC-UV for area % analysis and a different LC-MS method for peak identification. In addition, some synthetic intermediates might be chemically susceptible to the aqueous conditions used in RPLC separations. In this study, the use of supercritical fluid chromatography-photodiode array-electrospray ionization mass spectrometry (SFC-PDA-ESIMS) for fate and purge of two specified impurities in the 1-uridine starting material from the synthesis of a bis-piv 2'keto-uridine, an intermediate in the synthesis of uprifosbuvir, a treatment under investigation for chronic hepatitis C infection. Readily available SFC instrumentation with a Chiralpak IC column (4.6 × 150 mm, 3 μm) and ethanol: carbon dioxide based mobile phase eluent enabled the separation of closely related components from complex reaction mixtures where RLPC failed to deliver optimal chromatographic performance. These results illustrate how SFC combined with PDA and ESI-MS detection can become a powerful tool for direct impurity fate mapping across multiple reaction steps. Copyright © 2018 Elsevier B.V. All rights reserved.

Methodological assessment of the reduction of the content of impurities in nimodipine emulsion via the use of 21 amino acid protection

PubMed Central

Xie, Yiqiao; Zhuang, Zhiquan; Zhang, Shu; Xia, Zihua; Chen, De; Fan, Kaiyan; Ren, Jialin; Lin, CuiCui; Chen, Yanzhong; Yang, Fan

2017-01-01

Purpose The present study examined the factors affecting the content of impurities of nimodipine (NMP) emulsion and the associated methods of compound protection. Methods Destructive testing of NMP emulsion and its active pharmaceutical ingredient (API) were conducted, and ultracentrifugation was used to study the content of impurities in two phases. The impurity of NMP was measured under different potential of hydrogen (pH) conditions, antioxidants and pH-adjusting agents. Results Following destruction, the degradation of NMP notably occurred in the basic environment. The consumption of the pH-adjusting agent NaOH was proportional to the production of impurities since the inorganic base and/or acid promoted the degradation of NMP. The organic antioxidants, notably amino acids with an appropriate length of intermediate chain and electron-donating side group, exhibited improved antioxidant effects compared with inorganic antioxidants. The minimal amount of impurities was produced following addition of 0.04% lysine and 0.06% leucine in the aqueous phase and adjustment of the pH to a range of 7.5–8.0 in the presence of acetic acid solution. Conclusion NMP was more prone to degradation in an oxidative environment, in an aqueous phase and/or in the presence of inorganic pH-adjusting agents and antioxidants. The appropriate antioxidant and pH-adjusting agent should be selected according to the chemical structure, while destructive testing of the drug is considered to play the optimal protective effect. PMID:28490879

Development and validation of a liquid chromatographic method for the simultaneous determination of aniracetam and its related substances in the bulk drug and a tablet formulation.

PubMed

Papandreou, Georgios; Zorpas, Kostas; Archontaki, Helen

2011-11-01

Simultaneous determination of aniracetam and its related impurities (2-pyrrolidinone, p-anisic acid, 4-p-anisamidobutyric acid and (p-anisoyl)-4-methyl-2-pyrrolidinone) was accomplished in the bulk drug and in a tablet formulation using a high performance liquid chromatographic method with UV detection. Separation was achieved on a Hypersil BDS-CN column (150 mm × 4.0 mm, 5 μm) using a gradient elution program with solvent A composed of phosphate buffer (pH 4.0; 0.010 M) and solvent B of acetonitrile-phosphate buffer (pH 4.0; 0.010 M) (90:10, v/v). The flow rate of the mobile phase was 1.0 mL min(-1) and the total elution time, including the column re-equilibration, was approximately 20 min. The UV detection wavelength was varied appropriately among 210, 250 and 280 nm. Injection volume was 20 μL and experiments were conducted at ambient temperature. The developed method was validated in terms of system suitability, selectivity, linearity, range, precision, accuracy, limits of detection and quantification for the impurities, short term and long term stability of the analytes in the prepared solutions and robustness, following the ICH guidelines. Therefore, the proposed method was suitable for the simultaneous determination of aniracetam and its studied related impurities. Copyright © 2011 Elsevier B.V. All rights reserved.

Standing surface acoustic wave technology applied for micro-particle concentration in oil

NASA Astrophysics Data System (ADS)

Wang, Ziping; Xue, Xian; Luo, Ying; Yuan, Fuh-Gwo

2018-03-01

Oil lubrication plays an important role in a variety of mechanical equipment. The traditional purification method is difficult to remove the tiny impurity size of 5-15 μm. Three different types of the transducers and its preparation methods were used in the experiment. The phenomenon that the impurity particles in viscous fluid by the acoustic radiation force was moved the wave node position and focused on the center line was observed by the super-depth microscope. The influence factors of the produced SSAW, particle force condition and movement track were analyzed. The experimental results show that the interdigital transducer can be used to generate SSAW, so as to achieve the separation effect of oil and suspended particles.

The propagation and backscattering of soliton-like pulses in a chain of quartz beads and related problems. (II). Backscattering

NASA Astrophysics Data System (ADS)

Manciu, Marian; Sen, Surajit; Hurd, Alan J.

1999-12-01

We demonstrate that the propagation of solitons, soliton-like excitations and acoustic pulses discussed in the preceding article (M. Manciu, S. Sen and A.J. Hurd, Physica A, preceding article) can be used to detect buried impurities in a chain of elastic grains with Hertzian contacts. We also present preliminary data for 3D granular beds, where soliton-like objects can form and can be used to probe for buried impurities, thus suggesting that soliton-pulse spectroscopy has the potential to become a valuable tool for probing the structural properties of granular assemblies. The effects of restitution are briefly discussed. We refer to available experiments which support our contention.

Electronic structure of the Cu + impurity center in sodium chloride

NASA Astrophysics Data System (ADS)

Chermette, H.; Pedrini, C.

1981-08-01

The multiple-scattering Xα method is used to describe the electronic structure of Cu+ in sodium chloride. Several improvements are brought to the conventional Xα calculation. In particular, the cluster approximation is used by taking into account external lattice potential. The ''transition state'' procedure is applied in order to get the various multiplet levels. The fine electronic structure of the impurity centers is obtained after a calculation of the spin-orbit interactions. These results are compared with those given by a modified charge-consistent extended Hückel method (Fenske-type calculation) and the merit of each method is discussed. The present calculation produces good quantitative agreement with experiment concerning mainly the optical excitations and the emission mechanism of the Cu+ luminescent centers in NaCl.

Poloidal velocity of impurity ions in neoclassical theory

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

Wong, S. K.; Chan, V. S.; Solomon, W. M.

A formula for the poloidal velocity of impurity ions in a two-species plasma is derived from neoclassical theory in the banana regime, with corrections from the boundary layer separating the trapped and transiting ions. The formula is applicable to plasmas with toroidal rotations that can approach the thermal speeds of the ions. Using the formula to determine the poloidal velocity of C{sup +6} ions in a recently reported experiment [W. M. Solomon et al., Phys. Plasmas 13, 056116 (2006)] leads to agreement in the direction of the central region when it is otherwise from theories without strong toroidal rotations. Comparisonsmore » among these theories are made, demonstrating the degree of uncertainty of theoretical predictions.« less

Development of a real-time simulation tool towards self-consistent scenario of plasma start-up and sustainment on helical fusion reactor FFHR-d1

NASA Astrophysics Data System (ADS)

Goto, T.; Miyazawa, J.; Sakamoto, R.; Suzuki, Y.; Suzuki, C.; Seki, R.; Satake, S.; Huang, B.; Nunami, M.; Yokoyama, M.; Sagara, A.; the FFHR Design Group

2017-06-01

This study closely investigates the plasma operation scenario for the LHD-type helical reactor FFHR-d1 in view of MHD equilibrium/stability, neoclassical transport, alpha energy loss and impurity effect. In 1D calculation code that reproduces the typical pellet discharges in LHD experiments, we identify a self-consistent solution of the plasma operation scenario which achieves steady-state sustainment of the burning plasma with a fusion gain of Q ~ 10 was found within the operation regime that has been already confirmed in LHD experiment. The developed calculation tool enables systematic analysis of the operation regime in real time.

A New Platform for Profiling Degradation-Related Impurities Via Exploiting the Opportunities Offered by Ion-Selective Electrodes: Determination of Both Diatrizoate Sodium and Its Cytotoxic Degradation Product.

PubMed

Riad, Safaa M; Abd El-Rahman, Mohamed K; Fawaz, Esraa M; Shehata, Mostafa A

2018-05-01

Although the ultimate goal of administering active pharmaceutical ingredients (APIs) is to save countless lives, the presence of impurities and/or degradation products in APIs or formulations may cause harmful physiological effects. Today, impurity profiling (i.e., the identity as well as the quantity of impurity in a pharmaceutical) is receiving critical attention from regulatory authorities. Despite the predominant use of spectroscopic and chromatographic methods over electrochemical methods for impurity profiling of APIs, this work investigates the opportunities offered by electroanalytical methods, particularly, ion-selective electrodes (ISEs), for profiling degradation-related impurities (DRIs) compared with conventional spectroscopic and chromatographic methods. For a meaningful comparison, diatrizoate sodium (DTA) was chosen as the anionic X-ray contrast agent based on its susceptibility to deacetylation into its cytotoxic and mutagenic degradation product, 3,5-diamino-2,4,6 triiodobenzoic acid (DTB). This cationic diamino compound can be also detected as an impurity in the final product because it is used as a synthetic precursor for the synthesis of DTA. In this study, four novel sensitive and selective sensors for the determination of both DTA and its cytotoxic degradation products are presented. Sensors I and II were developed for the determination of the anionic drug, DTA, and sensors III and IV were developed for the determination of the cationic cytotoxic impurity. The use of these novel sensors not only provides a stability-indicating method for the selective determination of DTA in the presence of its degradation product, but also permits DRI profiling. Moreover, a great advantage of these proposed ISE systems is their higher sensitivity for the quantification of DTB relative to other spectroscopic and chromatographic methods, so it can measure trace amounts of DTB impurities in DTA bulk powder and pharmaceutical formulation without a need for preliminary separation.

DFT+U Study of Chemical Impurities in PuO 2

DOE PAGES

Hernandez, Sarah C.; Holby, Edward F.

2016-05-24

In this paper, we employ density functional theory to explore the effects of impurities in the fluorite crystal structure of PuO 2. The impurities that were considered are known impurities that exist in metallic δ-phase Pu, including H, C, Fe, and Ga. These impurities were placed at various high-symmetry sites within the PuO 2 structure including an octahedral interstitial site, an interstitial site with coordination to two neighboring O atoms, an O substitutional site, and a Pu substitutional site. Incorporation energies were calculated to be energetically unfavorable for all sites except the Pu substitutional site. When impurities were placed inmore » a Pu substitutional site, complexes incorporating the impurities and O formed within the PuO 2 structure. The observed defect-oxygen structures were OH, CO 3, FeO 5, and GaO 3. The presence of these defects led to distortion of the surrounding O atoms within the structure, producing long-range disorder of O atoms. In contrast, perturbations of Pu atoms had a relatively short-range effect on the relaxed structures. These effects are demonstrated via radial distribution functions for O and Pu vacancies. Calculated electronic structure revealed hybridization of the impurity atom with the O valence states and a relative decrease in the Pu 5f states. Minor differences in band gaps were observed for the defected PuO 2 structures containing H, C, and Ga. Finally, Fe-containing structures, however, were calculated to have a significantly decreased band gap, where the implementation of a Hubbard U parameter on the Fe 3d orbitals will maintain the calculated PuO 2 band gap.« less

Improvement of the ab initio embedded cluster method for luminescence properties of doped materials by taking into account impurity induced distortions: the example of Y2O3:Bi(3+).

PubMed

Réal, Florent; Ordejón, Belén; Vallet, Valérie; Flament, Jean-Pierre; Schamps, Joël

2009-11-21

New ab initio embedded-cluster calculations devoted to simulating the electronic spectroscopy of Bi(3+) impurities in Y(2)O(3) sesquioxide for substitutions in either S(6) or C(2) cationic sites have been carried out taking special care of the quality of the environment. A considerable quantitative improvement with respect to previous studies [F. Real et al. J. Chem. Phys. 125, 174709 (2006); F. Real et al. J. Chem. Phys. 127, 104705 (2007)] is brought by using environments of the impurities obtained via supercell techniques that allow the whole (pseudo) crystal to relax (WCR geometries) instead of environments obtained from local relaxation of the first coordination shell only (FSR geometries) within the embedded cluster approach, as was done previously. In particular the uniform 0.4 eV discrepancy of absorption energies found previously with FSR environments disappears completely when the new WCR environments of the impurities are employed. Moreover emission energies and hence Stokes shifts are in much better agreement with experiment. These decisive improvements are mainly due to a lowering of the local point-group symmetry (S(6)-->C(3) and C(2)-->C(1)) when relaxing the geometry of the emitting (lowest) triplet state. This symmetry lowering was not observed in FSR embedded cluster relaxations because the crystal field of the embedding frozen at the genuine pure crystal positions seems to be a more important driving force than the interactions within the cluster, thus constraining the overall symmetry of the system. Variations of the doping rate are found to have negligible influence on the spectra. In conclusion, the use of WCR environments may be crucial to render the structural distortions occurring in a doped crystal and it may help to significantly improve the embedded-cluster methodology to reach the quantitative accuracy necessary to interpret and predict luminescence properties of doped materials of this type.

Statics and dynamics of atomic dark-bright solitons in the presence of impurities

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

Achilleos, V.; Frantzeskakis, D. J.; Kevrekidis, P. G.

2011-11-15

Adopting a mean-field description for a two-component atomic Bose-Einstein condensate, we study the statics and dynamics of dark-bright solitons in the presence of localized impurities. We use adiabatic perturbation theory to derive an equation of motion for the dark-bright soliton center. We show that, counterintuitively, an attractive (repulsive) delta-like impurity, acting solely on the bright-soliton component, induces an effective localized barrier (well) in the effective potential felt by the soliton; this way, dark-bright solitons are reflected from (transmitted through) attractive (repulsive) impurities. Our analytical results for the small-amplitude oscillations of solitons are found to be in good agreement with resultsmore » obtained via a Bogoliubov-de Gennes analysis and direct numerical simulations.« less

Impurity incorporation, deposition kinetics, and microstructural evolution in sputtered Ta films

NASA Astrophysics Data System (ADS)

Whitacre, Jay Fredric

There is an increasing need to control the microstructure in thin sputtered Ta films for application as high-temperature coatings or diffusion barriers in microelectronic interconnect structures. To this end, the relationship between impurity incorporation, deposition kinetics, and microstructural evolution was examined for room-temperature low growth rate DC magnetron sputtered Ta films. Impurity levels present during deposition were controlled by pumping the chamber to various base pressures before growth. Ar pressures ranging from 2 to 20 mTorr were used to create contrasting kinetic environments in the sputter gas. This affected both the distribution of adatom kinetic energies at the substrate as well as the rate of impurity desorption from the chamber walls: at higher Ar pressures adatoms has lower kinetic energies, and there was an increase in impurity concentration. X-ray diffraction, high-resolution transmission electron microscopy (HREM), transmission electron diffraction (TED), scanning electron microscopy (SEM), secondary ion mass spectrometry (SIMS), and x-ray photoelectron. spectroscopy (XPS) were used to examine film crystallography, microstructure, and composition. A novel laboratory-based in-situ x-ray diffractometer was constructed. This new set-up allowed for the direct observation of microstructural evolution during growth. Films deposited at increasingly higher Ar pressures displayed a systematic decrease in grain size and degree of texturing, while surface morphology was found to vary from a nearly flat surface to a rough surface with several length scales of organization. In-situ x-ray results showed that the rate of texture evolution was found to be much higher in films grown using lower Ar pressures. These effects were studied in films less than 200 A thick using high resolution x-ray diffraction in conjunction with a synchrotron light source (SSRL B.L. 7-2). Films grown using higher Ar pressures (above 10 mTorr) with a pre-growth base pressure of 1 x 10--6 Torr had grains less than 10 nm in diameter and significant amorphous content Calculated radial distribution functions show a significant increase in average inter-atomic spacing in films grown using higher base pressures and Ar pressures. The amorphous content in the films was determined via comparison between ideal crystalline diffraction patterns and actual data. Thinner films grown at higher Ar pressures had relatively greater amorphous content. Real-time process control using the in-situ diffractometer was also demonstrated. The effects observed are discussed in the context of previous theories and experiments that document room-temperature sputter film growth. The changes in film microstructure observed were impurity mediated. Specifically, oxygen desorbed from the chamber walls during growth were incorporated into the film and subsequently limited grain development and texturing. A second phase consisting of amorphous Ta2O5 formed between the grain nuclei. Adatom kinetics played a role in determining surface morphology: at low Ar pressures (2 mTorr) significant adatom kinetic energies served to flattened the film surface, though impurity levels dominated grain development even in these conditions.

Subsurface segregation of yttria in yttria stabilized zirconia

NASA Astrophysics Data System (ADS)

de Ridder, M.; van Welzenis, R. G.; van der Gon, A. W. Denier; Brongersma, H. H.; Wulff, S.; Chu, W.-F.; Weppner, W.

2002-09-01

The segregation behavior in 3 and 10 mol % polycrystalline yttria stabilized zirconia (YSZ), calcined at temperatures ranging from 300 to 1600 degC, is characterized using low-energy ion scattering (LEIS). In order to be able to separate the Y and Zr LEIS signals, YSZ samples have been prepared using isotopically enriched 94ZrO2 instead of natural zirconia. The samples are made via a special precipitation method at a low temperature. The segregation to the outermost surface layer is dominated by impurities. The increased impurity levels are restricted to this first layer, which underlines the importance of the use of LEIS for this study. For temperatures of 1000 degC and higher, the oxides of the impurities Na, Si, and Ca even cover the surface completely. The performance of a device like the solid oxide fuel cell which has an YSZ electrolyte and a working temperature around 1000 degC, will, therefore, be strongly hampered by these impurities. The reduction of impurities, to prevent accumulation at the surface, will only be effective if the total impurity bulk concentration can be reduced below the 10 ppm level. Due to the presence of the impurities, yttria cannot accumulate in the outermost layer. It does so, in contrast to the general belief, in the subsurface layer and to much higher concentrations than the values reported previously. The difference in the interfacial free energies of Y2O3 and ZrO2 is determined to be -21plus-or-minus3 kJ/mol.

MS(n) , LC-MS-TOF and LC-PDA studies for identification of new degradation impurities of bupropion.

PubMed

Bansal, Rohit; Saini, Balraj; Bansal, Yogita; Bansal, Gulshan

2013-11-01

Three new degradation impurities of bupropion were characterized through high performance liquid chromatography coupled to photodiode array detection and to time-of-flight mass spectrometry. Bupropion was subjected to the ICH prescribed stress conditions. It degraded to seven impurities (I-VII) in alkaline hydrolytic conditions which were optimally resolved on an XTerra C18 column (250 × 4.6 mm, 5 µm) with a ternary mobile phase comprising ammonium formate (20 mm, pH 4.0), methanol and acetonitrile (75:10:15, v/v). The degradation impurities (III-V and VII) were characterized on the basis of mass fragmentation pattern of drug, accurate mass spectral and photodiode array data of the drug and degradation impurities. Compound V was found to be a known degradation impurity [1-hydroxy-1-(3-chlorophenyl)propan-2-one], whereas III, IV and VII were characterized as 2-hydroxy-2-(3'-chlorophenyl)-3,5,5-trimethylmorpholine, (2,4,4-trimethyl-1,3-oxazolidin-2-yl)(3-chlorophenyl)-methanone and 2-(3'-chlorophenyl)-3,5,5-trimethylmorphol-2-ene, respectively. Compound III was a known metabolite of the drug. This additional information on the degradation impurities can help in the development of a new stability-indicating assay method to monitor the stability of the drug product during its shelf-life as well as in development of a drug product with increased shelf-life. Copyright © 2013 John Wiley & Sons, Ltd.

Classical impurities and boundary Majorana zero modes in quantum chains

NASA Astrophysics Data System (ADS)

Müller, Markus; Nersesyan, Alexander A.

2016-09-01

We study the response of classical impurities in quantum Ising chains. The Z2 degeneracy they entail renders the existence of two decoupled Majorana modes at zero energy, an exact property of a finite system at arbitrary values of its bulk parameters. We trace the evolution of these modes across the transition from the disordered phase to the ordered one and analyze the concomitant qualitative changes of local magnetic properties of an isolated impurity. In the disordered phase, the two ground states differ only close to the impurity, and they are related by the action of an explicitly constructed quasi-local operator. In this phase the local transverse spin susceptibility follows a Curie law. The critical response of a boundary impurity is logarithmically divergent and maps to the two-channel Kondo problem, while it saturates for critical bulk impurities, as well as in the ordered phase. The results for the Ising chain translate to the related problem of a resonant level coupled to a 1d p-wave superconductor or a Peierls chain, whereby the magnetic order is mapped to topological order. We find that the topological phase always exhibits a continuous impurity response to local fields as a result of the level repulsion of local levels from the boundary Majorana zero mode. In contrast, the disordered phase generically features a discontinuous magnetization or charging response. This difference constitutes a general thermodynamic fingerprint of topological order in phases with a bulk gap.

Chemical Characterization and Thermal Stressing Studies of Perfluorohexane Fluids for Space-Based Applications

NASA Technical Reports Server (NTRS)

Arnold, William A.; Hartman, Thomas G.; McQuillen, John

2006-01-01

Perfluorohexane (PFH), C6F14, is a perfluorocarbon fluid. Several PFH fluids with different isomer concentrations were evaluated for use in an upcoming NASA space experiment. Samples tested included two commercially obtained high-purity n-perfluorohexane (n-PFH) fluids and a technical grade mixture of C6F14 branched and linear isomers (FC-72(TradeMark)). These fluids were evaluated for exact chemical composition, impurity purity and high temperature degradation behavior (pyrolysis). Our investigation involved simulated thermal stressing studies of PFH fluids under conditions likely to occur in the event of an atmospheric breach within the International Space Station (ISS) and subsequent exposure of the vapors to the high temperature and catalyst present in its Trace Contaminant Control Subsystem (TCCS). Exposure to temperatures in the temperature range of 200-450 C in an inert or oxidizing atmosphere, with and without the presence of catalyst was investigated. The most aggressive conditions studied were exposure of PFH vapors to 450 C in air and in the presence of TCCS (palladium) catalyst. Gas chromatography-mass spectrometry (GC-MS) and gas chromatography (GC) analyses were conducted on the perfluorohexane samples before and after pyrolysis. The FC-72 and n-PFH samples showed no significant degradation following pyrolysis even under the most aggressive study conditions. Some trace level impurities associated with the PFH samples such as linear perfluorocarbon monohydrides or monoiodides were destroyed by pyrolysis at the upper limit. Other trace level impurities such as olefinic or cycloolefinic perfluorocarbons were converted into oxidation products by pyrolysis. The purity of PFH following pyrolysis actually increased slightly as a consequence since these trace contaminants were effectively scrubbed from the samples. However, since the initial concentrations of the thermally-impacted impurities were so low, the net effect was trivial. A potential byproduct of exposure of perfluorohexane fluids to high temperatures is the production of perfluoroisobutene (PFiB), which is extremely toxic. An ultra-high sensitivity PFiB-specific analysis based on GC-MS with negative ion chemical ionization (NICI) detection was used to evaluate the samples following thermal stressing. The perfluorohexanes examined here under conditions reflective of the ISS TCCS environment showed no signs of PFiB production with an analytical detection limit of 10 part per billion (ppb v/v).

Gaseous trace impurity analyzer and method

DOEpatents

Edwards, Jr., David; Schneider, William

1980-01-01

Simple apparatus for analyzing trace impurities in a gas, such as helium or hydrogen, comprises means for drawing a measured volume of the gas as sample into a heated zone. A segregable portion of the zone is then chilled to condense trace impurities in the gas in the chilled portion. The gas sample is evacuated from the heated zone including the chilled portion. Finally, the chilled portion is warmed to vaporize the condensed impurities in the order of their boiling points. As the temperature of the chilled portion rises, pressure will develop in the evacuated, heated zone by the vaporization of an impurity. The temperature at which the pressure increase occurs identifies that impurity and the pressure increase attained until the vaporization of the next impurity causes a further pressure increase is a measure of the quantity of the preceding impurity.

Suitability of different containers for the sampling and storage of biogas and biomethane for the determination of the trace-level impurities--A review.

PubMed

Arrhenius, Karine; Brown, Andrew S; van der Veen, Adriaan M H

2016-01-01

The traceable and accurate measurement of biogas impurities is essential in order to robustly assess compliance with the specifications for biomethane being developed by CEN/TC408. An essential part of any procedure aiming to determinate the content of impurities is the sampling and the transfer of the sample to the laboratory. Key issues are the suitability of the sample container and minimising the losses of impurities during the sampling and analysis process. In this paper, we review the state-of-the-art in biogas sampling with the focus on trace impurities. Most of the vessel suitability studies reviewed focused on raw biogas. Many parameters need to be studied when assessing the suitability of vessels for sampling and storage, among them, permeation through the walls, leaks through the valves or physical leaks, sorption losses and adsorption effects to the vessel walls, chemical reactions and the expected initial concentration level. The majority of these studies looked at siloxanes, for which sampling bags, canisters, impingers and sorbents have been reported to be fit-for-purpose in most cases, albeit with some limitations. We conclude that the optimum method requires a combination of different vessels to cover the wide range of impurities commonly found in biogas, which have a wide range of boiling points, polarities, water solubilities, and reactivities. The effects from all the parts of the sampling line must be considered and precautions must be undertaken to minimize these effects. More practical suitability tests, preferably using traceable reference gas mixtures, are needed to understand the influence of the containers and the sampling line on sample properties and to reduce the uncertainty of the measurement. Copyright © 2015 Elsevier B.V. All rights reserved.

Study of impurity effects on CFETR steady-state scenario by self-consistent integrated modeling

NASA Astrophysics Data System (ADS)

Shi, Nan; Chan, Vincent S.; Jian, Xiang; Li, Guoqiang; Chen, Jiale; Gao, Xiang; Shi, Shengyu; Kong, Defeng; Liu, Xiaoju; Mao, Shifeng; Xu, Guoliang

2017-12-01

Impurity effects on fusion performance of China fusion engineering test reactor (CFETR) due to extrinsic seeding are investigated. An integrated 1.5D modeling workflow evolves plasma equilibrium and all transport channels to steady state. The one modeling framework for integrated tasks framework is used to couple the transport solver, MHD equilibrium solver, and source and sink calculations. A self-consistent impurity profile constructed using a steady-state background plasma, which satisfies quasi-neutrality and true steady state, is presented for the first time. Studies are performed based on an optimized fully non-inductive scenario with varying concentrations of Argon (Ar) seeding. It is found that fusion performance improves before dropping off with increasing {{Z}\\text{eff}} , while the confinement remains at high level. Further analysis of transport for these plasmas shows that low-k ion temperature gradient modes dominate the turbulence. The decrease in linear growth rate and resultant fluxes of all channels with increasing {{Z}\\text{eff}} can be traced to impurity profile change by transport. The improvement in confinement levels off at higher {{Z}\\text{eff}} . Over the regime of study there is a competition between the suppressed transport and increasing radiation that leads to a peak in the fusion performance at {{Z}\\text{eff}} (~2.78 for CFETR). Extrinsic impurity seeding to control divertor heat load will need to be optimized around this value for best fusion performance.

Effect of interfacial oxide layers on the current-voltage characteristics of Al-Si contacts

NASA Technical Reports Server (NTRS)

Porter, W. A.; Parker, D. L.

1976-01-01

Aluminum-silicon contacts with very thin interfacial oxide layers and various surface impurity concentrations are studied for both n and p-type silicon. To determine the surface impurity concentrations on p(+)-p and n(+)-n structures, a modified C-V technique was utilized. Effects of interfacial oxide layers and surface impurity concentrations on current-voltage characteristics are discussed based on the energy band diagrams from the conductance-voltage plots. The interfacial oxide and aluminum layer causes image contrasts on X-ray topographs.

Detection of dehalogenation impurities in organohalogenated pharmaceuticals by UHPLC-DAD-HRESIMS.

PubMed

Regalado, Erik L; Dermenjian, Renee K; Joyce, Leo A; Welch, Christopher J

2014-04-01

The presence of dehalogenated impurities is often observed in halogen-containing pharmaceuticals, and can present a difficult analytical challenge, as the chromatographic behavior of the halogenated drug and the hydrogen-containing analog can be quite similar. In this study we describe the chromatographic separation and unambiguous identification of dehalogenation impurities or associated isomers in organohalogenated pharmaceuticals using UHPLC with a pentafluorophenyl column coupled with diode-array and high resolution electrospray ionization mass spectrometry detection (UHPLC-DAD-HRESIMS). Copyright © 2014 Elsevier B.V. All rights reserved.

Electronic structure and optical properties of triangular GaAs/AlGaAs quantum dots: Exciton and impurity states

NASA Astrophysics Data System (ADS)

Tiutiunnyk, A.; Akimov, V.; Tulupenko, V.; Mora-Ramos, M. E.; Kasapoglu, E.; Ungan, F.; Sökmen, I.; Morales, A. L.; Duque, C. A.

2016-03-01

Electronic structure and optical properties in equilateral triangular GaAs/Al0.3Ga0.7As quantum dots are studied extensively. The effects of donor and acceptor impurity atoms positioned in the orthocenter of the triangle, as well as of the external DC electric field are taken into account. Binding energies of the impurity, exciton energies, interband photoluminescence peak positions as well as linear and non-linear optical properties in THz range caused by transitions between excitonic states are calculated and discussed.

Interaction of ions, atoms, and small molecules with quantized vortex lines in superfluid (4)He.

PubMed

Mateo, David; Eloranta, Jussi; Williams, Gary A

2015-02-14

The interaction of a number of impurities (H2, Ag, Cu, Ag2, Cu2, Li, He3 (+), He(*) ((3)S), He2 (∗) ((3)Σu), and e(-)) with quantized rectilinear vortex lines in superfluid (4)He is calculated by using the Orsay-Trento density functional theory (DFT) method at 0 K. The Donnelly-Parks (DP) potential function binding ions to the vortex is combined with DFT data, yielding the impurity radius as well as the vortex line core parameter. The vortex core parameter at 0 K (0.74 Å) obtained either directly from the vortex line geometry or through the DP potential fitting is smaller than previously suggested but is compatible with the value obtained from re-analysis of the Rayfield-Reif experiment. All of the impurities have significantly higher binding energies to vortex lines below 1 K than the available thermal energy, where the thermally assisted escape process becomes exponentially negligible. Even at higher temperatures 1.5-2.0 K, the trapping times for larger metal clusters are sufficiently long that the previously observed metal nanowire assembly in superfluid helium can take place at vortex lines. The binding energy of the electron bubble is predicted to decrease as a function of both temperature and pressure, which allows adjusting the trap depth for either permanent trapping or to allow thermally assisted escape. Finally, a new scheme for determining the trapping of impurities on vortex lines by optical absorption spectroscopy is outlined and demonstrated for He(*).

Interaction of ions, atoms, and small molecules with quantized vortex lines in superfluid 4He

NASA Astrophysics Data System (ADS)

Mateo, David; Eloranta, Jussi; Williams, Gary A.

2015-02-01

The interaction of a number of impurities (H2, Ag, Cu, Ag2, Cu2, Li, He3 + , He* (3S), He2∗ (3Σu), and e-) with quantized rectilinear vortex lines in superfluid 4He is calculated by using the Orsay-Trento density functional theory (DFT) method at 0 K. The Donnelly-Parks (DP) potential function binding ions to the vortex is combined with DFT data, yielding the impurity radius as well as the vortex line core parameter. The vortex core parameter at 0 K (0.74 Å) obtained either directly from the vortex line geometry or through the DP potential fitting is smaller than previously suggested but is compatible with the value obtained from re-analysis of the Rayfield-Reif experiment. All of the impurities have significantly higher binding energies to vortex lines below 1 K than the available thermal energy, where the thermally assisted escape process becomes exponentially negligible. Even at higher temperatures 1.5-2.0 K, the trapping times for larger metal clusters are sufficiently long that the previously observed metal nanowire assembly in superfluid helium can take place at vortex lines. The binding energy of the electron bubble is predicted to decrease as a function of both temperature and pressure, which allows adjusting the trap depth for either permanent trapping or to allow thermally assisted escape. Finally, a new scheme for determining the trapping of impurities on vortex lines by optical absorption spectroscopy is outlined and demonstrated for He*.

Quasiparticle density of states, localization, and distributed disorder in the cuprate superconductors

NASA Astrophysics Data System (ADS)

Sulangi, Miguel Antonio; Zaanen, Jan

2018-04-01

We explore the effects of various kinds of random disorder on the quasiparticle density of states of two-dimensional d -wave superconductors using an exact real-space method, incorporating realistic details known about the cuprates. Random on-site energy and pointlike unitary impurity models are found to give rise to a vanishing DOS at the Fermi energy for narrow distributions and low concentrations, respectively, and lead to a finite, but suppressed, DOS at unrealistically large levels of disorder. Smooth disorder arising from impurities located away from the copper-oxide planes meanwhile gives rise to a finite DOS at realistic impurity concentrations. For the case of smooth disorder whose average potential is zero, a resonance is found at zero energy for the quasiparticle DOS at large impurity concentrations. We discuss the implications of these results on the computed low-temperature specific heat, the behavior of which we find is strongly affected by the amount of disorder present in the system. We also compute the localization length as a function of disorder strength for various types of disorder and find that intermediate- and high-energy states are quasiextended for low disorder, and that states near the Fermi energy are strongly localized and have a localization length that exhibits an unusual dependence on the amount of disorder. We comment on the origin of disorder in the cuprates and provide constraints on these based on known results from scanning tunneling spectroscopy and specific heat experiments.

First-principles studies of electron transport in Ga2O3

NASA Astrophysics Data System (ADS)

Kang, Youngho; Krishnaswamy, Karthik; Peelaers, Hartwin; van de Walle, Chris G.

Ga2O3 is a wide-gap semiconductor with a monoclinic crystal structure and a band gap of 4.8 eV. Its high carrier mobility and large band gap have attracted a lot of attention for use in high power electronics and transparent conductors. Despite its potential for adoption in these applications, an understanding of its carrier transport properties is still lacking. In this study we use first-principles calculations to analyze and compute the electron scattering rates in Ga2O3. Scattering due to ionized impurities and polar longitudinal-optical (LO) phonon is taken into account. We find that the electron mobility is nearly isotropic, despite the low-symmetry monoclinic structure of Ga2O3. At low carrier densities ( 1017 cm-3), the mobility is limited by LO phonon scattering. Scattering by ionized impurities becomes increasingly important at higher carrier densities. This type of scattering is enhanced when compensating native point defects are present; in particular, gallium vacancies, which are triply negatively charged, can have a strong effect on mobility. These effects explain the downturn in mobility observed in experiments at high carrier densities. This work was supported by ARO and NSF.

Theory of copper impurities in ZnO

NASA Astrophysics Data System (ADS)

Lyons, John; Alkauskas, Audrius; Janotti, Anderson; van de Walle, Chris G.

Due to its connection to deep luminescence signals and its potential use as an acceptor dopant, copper has been one the most studied impurities in ZnO. From experiment, copper incorporating on the Zn site (CuZn) is known to lead to an acceptor level residing near the conduction band of ZnO, making CuZn an exceedingly deep acceptor. CuZn in ZnO has also long been linked with broad 2.4 eV green luminescence (GL) signals. In this work we explore the electrical and optical properties of Cu in ZnO using density functional theory (DFT). Due to the limitations of traditional forms of DFT, an accurate theoretical description of the electrical and optical properties of such deep centers has been difficult to achieve. Here we employ a screened hybrid density functional (HSE) to calculate the properties of Cu in ZnO. We determine the thermodynamic transition levels associated with CuZn in ZnO as well as the associated luminescence lineshapes of characteristic optical transitions. We find that HSE-calculated optical transitions are in close agreement with experimental studies. This work was supported in part by NSF and by ARO.

Impurity bound states in fully gapped d-wave superconductors with subdominant order parameters

PubMed Central

Mashkoori, Mahdi; Björnson, Kristofer; Black-Schaffer, Annica M.

2017-01-01

Impurities in superconductors and their induced bound states are important both for engineering novel states such as Majorana zero-energy modes and for probing bulk properties of the superconducting state. The high-temperature cuprates offer a clear advantage in a much larger superconducting order parameter, but the nodal energy spectrum of a pure d-wave superconductor only allows virtual bound states. Fully gapped d-wave superconducting states have, however, been proposed in several cuprate systems thanks to subdominant order parameters producing d + is- or d + id′-wave superconducting states. Here we study both magnetic and potential impurities in these fully gapped d-wave superconductors. Using analytical T-matrix and complementary numerical tight-binding lattice calculations, we show that magnetic and potential impurities behave fundamentally different in d + is- and d + id′-wave superconductors. In a d + is-wave superconductor, there are no bound states for potential impurities, while a magnetic impurity produces one pair of bound states, with a zero-energy level crossing at a finite scattering strength. On the other hand, a d + id′-wave symmetry always gives rise to two pairs of bound states and only produce a reachable zero-energy level crossing if the normal state has a strong particle-hole asymmetry. PMID:28281570

Effects of Thickness of a Low-Temperature Buffer and Impurity Incorporation on the Characteristics of Nitrogen-polar GaN.

PubMed

Yang, Fann-Wei; Chen, Yu-Yu; Feng, Shih-Wei; Sun, Qian; Han, Jung

2016-12-01

In this study, effects of the thickness of a low temperature (LT) buffer and impurity incorporation on the characteristics of Nitrogen (N)-polar GaN are investigated. By using either a nitridation or thermal annealing step before the deposition of a LT buffer, three N-polar GaN samples with different thicknesses of LT buffer and different impurity incorporations are prepared. It is found that the sample with the thinnest LT buffer and a nitridation step proves to be the best in terms of a fewer impurity incorporations, strong PL intensity, fast mobility, small biaxial strain, and smooth surface. As the temperature increases at ~10 K, the apparent donor-acceptor-pair band is responsible for the decreasing integral intensity of the band-to-band emission peak. In addition, the thermal annealing of the sapphire substrates may cause more impurity incorporation around the HT-GaN/LT-GaN/sapphire interfacial regions, which in turn may result in a lower carrier mobility, larger biaxial strain, larger bandgap shift, and stronger yellow luminescence. By using a nitridation step, both a thinner LT buffer and less impurity incorporation are beneficial to obtaining a high quality N-polar GaN.

Signatures of two-step impurity mediated vortex lattice melting in Bose-Einstein condensate

NASA Astrophysics Data System (ADS)

Dey, Bishwajyoti

2017-04-01

We study impurity mediated vortex lattice melting in a rotating two-dimensional Bose-Einstein condensate (BEC). Impurities are introduced either through a protocol in which vortex lattice is produced in an impurity potential or first creating the vortex lattice in the absence of random pinning and then cranking up the impurity potential. These two protocols have obvious relation with the two commonly known protocols of creating vortex lattice in a type-II superconductor: zero field cooling protocol and the field cooling protocol respectively. Time-splitting Crank-Nicolson method has been used to numerically simulate the vortex lattice dynamics. It is shown that the vortex lattice follows a two-step melting via loss of positional and orientational order. This vortex lattice melting process in BEC closely mimics the recently observed two-step melting of vortex matter in weakly pinned type-II superconductor Co-intercalated NbSe2. Also, using numerical perturbation analysis, we compare between the states obtained in two protocols and show that the vortex lattice states are metastable and more disordered when impurities are introduced after the formation of an ordered vortex lattice. The author would like to thank SERB, Govt. of India and BCUD-SPPU for financial support through research Grants.

Origin and roles of oxygen impurities in hexagonal boron nitride epilayers

NASA Astrophysics Data System (ADS)

Grenadier, S. J.; Maity, A.; Li, J.; Lin, J. Y.; Jiang, H. X.

2018-04-01

Photoluminescence emission spectroscopy and electrical transport measurements have been employed to study the origin and roles of oxygen impurities in hexagonal boron nitride (h-BN) epilayers grown on sapphire substrates. The temperature dependence of the electrical resistivity revealed the presence of a previously unnoticed impurity level of about 0.6 eV in h-BN epilayers grown at high temperatures. The results suggested that in addition to the common nitrogen vacancy (VN) shallow donors in h-BN, oxygen impurities diffused from sapphire substrates during high temperature growth also act as substitutional donors (ON). The presence of ON gives rise to an additional emission peak in the photoluminescence spectrum, corresponding to a donor-acceptor pair recombination involving the ON donor and the CN (carbon occupying nitrogen site) deep level acceptor. Moreover, due to the presence of ON donors, the majority charge carrier type changed to electrons in epilayers grown at high temperatures, in contrast to typical h-BN epilayers which naturally exhibit "p-type" character. The results provided a more coherent picture for common impurities/defects in h-BN as well as a better understanding of the growth mediated impurities in h-BN epilayers, which will be helpful for finding possible ways to further improve the quality and purity of this emerging material.

Elemental Impurities in Pharmaceutical Excipients.

PubMed

Li, Gang; Schoneker, Dave; Ulman, Katherine L; Sturm, Jason J; Thackery, Lisa M; Kauffman, John F

2015-12-01

Control of elemental impurities in pharmaceutical materials is currently undergoing a transition from control based on concentrations in components of drug products to control based on permitted daily exposures in drug products. Within the pharmaceutical community, there is uncertainty regarding the impact of these changes on manufactures of drug products. This uncertainty is fueled in part by a lack of publically available information on elemental impurity levels in common pharmaceutical excipients. This paper summarizes a recent survey of elemental impurity levels in common pharmaceutical excipients as well as some drug substances. A widely applicable analytical procedure was developed and was shown to be suitable for analysis of elements that are subject to United States Pharmacopoeia Chapter <232> and International Conference on Harmonization's Q3D Guideline on Elemental Impurities. The procedure utilizes microwave-assisted digestion of pharmaceutical materials and inductively coupled plasma mass spectrometry for quantitative analysis of these elements. The procedure was applied to 190 samples from 31 different excipients and 15 samples from eight drug substances provided through the International Pharmaceutical Excipient Council of the Americas. The results of the survey indicate that, for the materials included in the study, relatively low levels of elemental impurities are present. © 2015 The Authors. Journal of Pharmaceutical Sciences published by Wiley Periodicals, Inc. and the American Pharmacists Association.

Impurity bubbles in a BEC

NASA Astrophysics Data System (ADS)

Timmermans, Eddy; Blinova, Alina; Boshier, Malcolm

2013-05-01

Polarons (particles that interact with the self-consistent deformation of the host medium that contains them) self-localize when strongly coupled. Dilute Bose-Einstein condensates (BECs) doped with neutral distinguishable atoms (impurities) and armed with a Feshbach-tuned impurity-boson interaction provide a unique laboratory to study self-localized polarons. In nature, self-localized polarons come in two flavors that exhibit qualitatively different behavior: In lattice systems, the deformation is slight and the particle is accompanied by a cloud of collective excitations as in the case of the Landau-Pekar polarons of electrons in a dielectric lattice. In natural fluids and gases, the strongly coupled particle radically alters the medium, e.g. by expelling the host medium as in the case of the electron bubbles in superfluid helium. We show that BEC-impurities can self-localize in a bubble, as well as in a Landau-Pekar polaron state. The BEC-impurity system is fully characterized by only two dimensionless coupling constants. In the corresponding phase diagram the bubble and Landau-Pekar polaron limits correspond to large islands separated by a cross-over region. The same BEC-impurity species can be adiabatically Feshbach steered from the Landau-Pekar to the bubble regime. This work was funded by the Los Alamos LDRD program.

Scaling of Tripartite Entanglement at Impurity Quantum Phase Transitions.

PubMed

Bayat, Abolfazl

2017-01-20

The emergence of a diverging length scale in many-body systems at a quantum phase transition implies that total entanglement has to reach its maximum there. In order to fully characterize this, one has to consider multipartite entanglement as, for instance, bipartite entanglement between individual particles fails to signal this effect. However, quantification of multipartite entanglement is very hard, and detecting it may not be possible due to the lack of accessibility to all individual particles. For these reasons it will be more sensible to partition the system into relevant subsystems, each containing a few to many spins, and study entanglement between those constituents as a coarse-grain picture of multipartite entanglement between individual particles. In impurity systems, famously exemplified by two-impurity and two-channel Kondo models, it is natural to divide the system into three parts, namely, impurities and the left and right bulks. By exploiting two tripartite entanglement measures, based on negativity, we show that at impurity quantum phase transitions the tripartite entanglement diverges and shows scaling behavior. While the critical exponents are different for each tripartite entanglement measure, they both provide very similar critical exponents for the two-impurity and the two-channel Kondo models, suggesting that they belong to the same universality class.

Role of oxygen impurities in synthesis of iron mononitride thin films

NASA Astrophysics Data System (ADS)

Niti, Seema, Gupta, Mukul

2018-04-01

In this work we have studied iron mononitride (FeN) thin films. FeN is debated for its structure and often a mixed phase is obtained experimentally. Even in single phases of FeN obtain so far, an additional phase was always found even though its volume fraction was minimal. Such phases have been claimed to stem from impurities due to partial oxidation taking place during the growth. In order to study the nature of such impurities, we have deliberately introduced oxygen during the growth of FeN in a magnetron sputtering process. We found that the presence of oxygen tends to distort the tetrahedral symmetry as envisaged in the N K edge absorption spectra. The effect of oxygen impurities is subtler on the long range ordering due to formation of a disordered phase. Obtained results can be used to find the pathways to prepare a single phase FeN compound and thereafter to resolve the debate about its structure and the magnetic ground state.

Identification, preparation and UHPLC determination of process-related impurity in zolmitriptan.

PubMed

Douša, Michal; Gibala, Petr; Rádl, Stanislav; Klecán, Ondřej; Mandelová, Zuzana; Břicháč, Jiří; Pekárek, Tomáš

2012-01-25

A new impurity was detected and determined using gradient ion-pair UHPLC method with UV detection in zolmitriptan (ZOL). Using MS, NMR and IR study the impurity was identified as (4S,4'S)-4,4'-(2,2'-(4-(dimethylamino)butane-1,1-diyl)bis(3-(2-(dimethylamino) ethyl)-1H-indole-5,2-diyl))bis(methylene)di(oxazolidin-2-one) (ZOL-dimer). The standard of ZOL-dimer was consequently prepared via organic synthesis followed by semipreparative HPLC purification. The UHPLC method was optimized in order to selectively detect and quantify other known and unknown process-related impurities and degradation products of ZOL as well. The presented method which was validated with respect to linearity, accuracy, precision and selectivity has an advantage of a very quick UHPLC chromatographic separation (less than 7 min including re-equilibration time) and therefore is highly suitable for routine analysis of related substances and stability studies of ZOL. Copyright © 2011 Elsevier B.V. All rights reserved.

Incorporation of impurity to a tetragonal lysozyme crystal

NASA Astrophysics Data System (ADS)

Kurihara, Kazuo; Miyashita, Satoru; Sazaki, Gen; Nakada, Toshitaka; Durbin, Stephen D.; Komatsu, Hiroshi; Ohba, Tetsuhiko; Ohki, Kazuo

1999-01-01

Concentration of a phosphor-labeled impurity (ovalbumin) incorporated into protein (hen egg white lysozyme) crystals during growth was measured by fluorescence.This technique enabled us to measure the local impurity concentration in a crystal quantitatively. Impurity concentration increased with growth rate, which could not be explained by two conventional models (equilibrium adsorption model and Burton-Prim-Slichter model); a modified model is proposed. Impurity concentration also increased with the pH of the solution. This result is discussed considering the electrostatic interaction between the impurity and the crystallizing species.

The effect of magnetic field on the impurity binding energy of shallow donor impurities in a Ga1−xInxNyAs1−y/GaAs quantum well

PubMed Central

2012-01-01

Using a variational approach, we have investigated the effects of the magnetic field, the impurity position, and the nitrogen and indium concentrations on impurity binding energy in a Ga1−xInxNyAs1−y/GaAs quantum well. Our calculations have revealed the dependence of impurity binding on the applied magnetic field, the impurity position, and the nitrogen and indium concentrations. PMID:23095253

One-Step Synthesis of B/N Co-doped Graphene as Highly Efficient Electrocatalyst for the Oxygen Reduction Reaction: Synergistic Effect of Impurities.

PubMed

Mazánek, Vlastimil; Matějková, Stanislava; Sedmidubský, David; Pumera, Martin; Sofer, Zdeněk

2018-01-19

In the last decade, numerous studies of graphene doping by various metal and nonmetal elements have been done in order to obtain tailored properties, such as non-zero band gap, electrocatalytic activity, or controlled optical properties. From nonmetal elements, boron and nitrogen were the most studied dopants. Recently, it has been shown that in some cases the enhanced electrocatalytic activity of graphene and its derivatives can be attributed to metal impurities rather than to nonmetal elements. In this paper, we investigated the electrocatalytical properties of B/N co-doped graphene with respect to the content of metallic impurities introduced by the synthesis procedures. For this purpose, a permanganate (Hummers) and a chlorate (Hofmann) route were used for the preparation of the starting graphene oxides (GO). The GO used for the synthesis of B/N co-doped graphene had significantly difference compositions of oxygen functionalities as well as metallic impurities introduced by the different synthetic procedures. We performed a detailed structural and chemical analysis of the doped graphene samples to correlate their electrocatalytic activity with the concentration of incorporated boron and nitrogen as well as metallic impurities. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantum interference on electron scattering in graphene by carbon impurities in underlying h -BN

NASA Astrophysics Data System (ADS)

Kaneko, Tomoaki; Koshino, Mikito; Saito, Riichiro

2017-03-01

Electronic structures and transport properties of graphene on h -BN with carbon impurities are investigated by first-principles calculation and the tight-binding model. We show that the coupling between the impurity level and the graphene's Dirac cone sensitively depends on the impurity position, and in particular, it nearly vanishes when the impurity is located right below the center of the six membered ring of graphene. The Bloch phase factor at the Brillouin zone edge plays a decisive role in the cancellation of the hopping integrals. The impurity position dependence on the electronic structures of graphene on h -BN is investigated by the first-principles calculation, and its qualitative feature is well explained by a tight-binding model with graphene and a single impurity site. We also propose a simple one-dimensional chain-impurity model to analytically describe the role of the quantum interference in the position-dependent coupling.

Effect of Iron Impurity on the Phase Composition, Structure and Properties of Magnesium Alloys Containing Manganese and Aluminum

NASA Astrophysics Data System (ADS)

Volkova, E. F.

2017-07-01

Results of a study of the interaction between iron impurity and manganese and aluminum alloying elements during formation of phase composition in alloys of the Mg - Mn, Mg - Al, Mg - Al - Mn, and Mg - Al - Zn - Mn systems are presented. It is proved that this interaction results in introduction of Fe into the intermetallic phase. The phase compositions of model magnesium alloys and commercial alloys MA2-1 and MA5 are studied. It is shown that both manganese and aluminum may bind the iron impurity into phases. Composite Fe-containing intermetallic phases of different compositions influence differently the corrosion resistance of magnesium alloys.

Impurity-limited resistance and phase interference of localized impurities under quasi-one dimensional nano-structures

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

Sano, Nobuyuki, E-mail: sano@esys.tsukuba.ac.jp

2015-12-28

The impurity-limited resistance and the effect of the phase interference among localized multiple impurities in the quasi-one dimensional (quasi-1D) nanowire structures are systematically investigated under the framework of the scattering theory. We derive theoretical expressions of the impurity-limited resistance in the nanowire under the linear response regime from the Landauer formula and from the Boltzmann transport equation (BTE) with the relaxation time approximation. We show that the formula from the BTE exactly coincides with that from the Landauer approach with the weak-scattering limit when the energy spectrum of the in-coming electrons from the reservoirs is narrow and, thus, point outmore » a possibility that the distinction of the impurity-limited resistances derived from the Landauer formula and that of the BTE could be made clear. The derived formulas are applied to the quasi-1D nanowires doped with multiple localized impurities with short-range scattering potential and the validity of various approximations on the resistance are discussed. It is shown that impurity scattering becomes so strong under the nanowire structures that the weak-scattering limit breaks down in most cases. Thus, both phase interference and phase randomization simultaneously play a crucial role in determining the impurity-limited resistance even under the fully coherent framework. When the impurity separation along the wire axis direction is small, the constructive phase interference dominates and the resistance is much greater than the average resistance. As the separation becomes larger, however, it approaches the series resistance of the single-impurity resistance due to the phase randomization. Furthermore, under the uniform configuration of impurities, the space-average resistance of multiple impurities at room temperature is very close to the series resistance of the single-impurity resistance, and thus, each impurity could be regarded as an independent scattering center. The physical origin of this “self-averaging” under the fully coherent environments is attributed to the broadness of the energy spectrum of the in-coming electrons from the reservoirs.« less

Isothermal titration calorimetry for measuring macromolecule-ligand affinity.

PubMed

Duff, Michael R; Grubbs, Jordan; Howell, Elizabeth E

2011-09-07

Isothermal titration calorimetry (ITC) is a useful tool for understanding the complete thermodynamic picture of a binding reaction. In biological sciences, macromolecular interactions are essential in understanding the machinery of the cell. Experimental conditions, such as buffer and temperature, can be tailored to the particular binding system being studied. However, careful planning is needed since certain ligand and macromolecule concentration ranges are necessary to obtain useful data. Concentrations of the macromolecule and ligand need to be accurately determined for reliable results. Care also needs to be taken when preparing the samples as impurities can significantly affect the experiment. When ITC experiments, along with controls, are performed properly, useful binding information, such as the stoichiometry, affinity and enthalpy, are obtained. By running additional experiments under different buffer or temperature conditions, more detailed information can be obtained about the system. A protocol for the basic setup of an ITC experiment is given.

Isothermal Titration Calorimetry for Measuring Macromolecule-Ligand Affinity

PubMed Central

Duff,, Michael R.; Grubbs, Jordan; Howell, Elizabeth E.

2011-01-01

Isothermal titration calorimetry (ITC) is a useful tool for understanding the complete thermodynamic picture of a binding reaction. In biological sciences, macromolecular interactions are essential in understanding the machinery of the cell. Experimental conditions, such as buffer and temperature, can be tailored to the particular binding system being studied. However, careful planning is needed since certain ligand and macromolecule concentration ranges are necessary to obtain useful data. Concentrations of the macromolecule and ligand need to be accurately determined for reliable results. Care also needs to be taken when preparing the samples as impurities can significantly affect the experiment. When ITC experiments, along with controls, are performed properly, useful binding information, such as the stoichiometry, affinity and enthalpy, are obtained. By running additional experiments under different buffer or temperature conditions, more detailed information can be obtained about the system. A protocol for the basic setup of an ITC experiment is given. PMID:21931288

Numerical renormalization group calculation of impurity internal energy and specific heat of quantum impurity models

NASA Astrophysics Data System (ADS)

Merker, L.; Costi, T. A.

2012-08-01

We introduce a method to obtain the specific heat of quantum impurity models via a direct calculation of the impurity internal energy requiring only the evaluation of local quantities within a single numerical renormalization group (NRG) calculation for the total system. For the Anderson impurity model we show that the impurity internal energy can be expressed as a sum of purely local static correlation functions and a term that involves also the impurity Green function. The temperature dependence of the latter can be neglected in many cases, thereby allowing the impurity specific heat Cimp to be calculated accurately from local static correlation functions; specifically via Cimp=(∂Eionic)/(∂T)+(1)/(2)(∂Ehyb)/(∂T), where Eionic and Ehyb are the energies of the (embedded) impurity and the hybridization energy, respectively. The term involving the Green function can also be evaluated in cases where its temperature dependence is non-negligible, adding an extra term to Cimp. For the nondegenerate Anderson impurity model, we show by comparison with exact Bethe ansatz calculations that the results recover accurately both the Kondo induced peak in the specific heat at low temperatures as well as the high-temperature peak due to the resonant level. The approach applies to multiorbital and multichannel Anderson impurity models with arbitrary local Coulomb interactions. An application to the Ohmic two-state system and the anisotropic Kondo model is also given, with comparisons to Bethe ansatz calculations. The approach could also be of interest within other impurity solvers, for example, within quantum Monte Carlo techniques.

Behavior of some singly ionized, heavy-ion impurities during compression in a theta-pinch plasma

NASA Technical Reports Server (NTRS)

Jalufka, N. W.

1975-01-01

The introduction of a small percentage of an impurity gas containing a desired element into a theta-pinch plasma is a standard procedure used to investigate the spectra and atomic processes of the element. This procedure assumes that the mixing ratio of impurity-to-fill gases remains constant during the collapse and heating phase. Spectroscopic investigations of the constant-mixing-ratio assumption for a 2% neon and argon impurity verifies the assumption only for the neon impurity. However, for the 2% argon impurity, only 20 to 25% of the argon is in the high-temperature compressed plasma. It is concluded that the constant-mixing-ratio assumption is not applicable to the argon impurity.

Silicon drift detector based X-ray spectroscopy diagnostic system for the study of non-thermal electrons at Aditya tokamak.

PubMed

Purohit, S; Joisa, Y S; Raval, J V; Ghosh, J; Tanna, R; Shukla, B K; Bhatt, S B

2014-11-01

Silicon drift detector based X-ray spectrometer diagnostic was developed to study the non-thermal electron for Aditya tokamak plasma. The diagnostic was mounted on a radial mid plane port at the Aditya. The objective of diagnostic includes the estimation of the non-thermal electron temperature for the ohmically heated plasma. Bi-Maxwellian plasma model was adopted for the temperature estimation. Along with that the study of high Z impurity line radiation from the ECR pre-ionization experiments was also aimed. The performance and first experimental results from the new X-ray spectrometer system are presented.

A review of radiative detachment studies in tokamak advanced magnetic divertor configurations

DOE PAGES

Soukhanovskii, V. A.

2017-04-28

The present vision for a plasma–material interface in the tokamak is an axisymmetric poloidal magnetic X-point divertor. Four tasks are accomplished by the standard poloidal X-point divertor: plasma power exhaust; particle control (D/T and He pumping); reduction of impurity production (source); and impurity screening by the divertor scrape-off layer. A low-temperature, low heat flux divertor operating regime called radiative detachment is viewed as the main option that addresses these tasks for present and future tokamaks. Advanced magnetic divertor configuration has the capability to modify divertor parallel and cross-field transport, radiative and dissipative losses, and detachment front stability. Advanced magnetic divertormore » configurations are divided into four categories based on their salient qualitative features: (1) multiple standard X-point divertors; (2) divertors with higher order nulls; (3) divertors with multiple X-points; and (4) long poloidal leg divertors (and also with multiple X-points). As a result, this paper reviews experiments and modeling in the area of radiative detachment in the advanced magnetic divertor configurations.« less

Interplay Between Electron-Electron, Electron-Impurity and Electron-Boundary Scattering in a Two Dimensional Electron Gas (2DEG)

NASA Astrophysics Data System (ADS)

Abraham, Mathew C.; Ram, Rajeev J.; Gossard, A. C.

2003-03-01

A small group of experiments have been conducted over the past decade that explore the fact that even though electron-electron (e-e) scattering in a 2DEG is momentum conserving, its interplay with electron-impurity (e-i)and electron-boundary (e-b) scattering can change the resistance of bulk and mesoscopic devices respectively. The interplay between e-e and e-i scattering in a bulk sample has been shown to cause a fall in the resistivity as a function of electron temperature in the regime where the scattering length l_ee > l_ei and a rise when l_ee < l_ei. In contrast, the interplay between e-e and e-b scattering has been demonstrated to raise the resistivity of a mesoscopic sized wire as a function of electron temperature in the regime l_ee > lb and a fall when l_ee < l_b. We attempt to present a comprehensive picture of these two apparently competing effects by studying devices that are affected by both phenomena simultaneously.

Microscopic observation of magnon bound states and their dynamics.

PubMed

Fukuhara, Takeshi; Schauß, Peter; Endres, Manuel; Hild, Sebastian; Cheneau, Marc; Bloch, Immanuel; Gross, Christian

2013-10-03

The existence of bound states of elementary spin waves (magnons) in one-dimensional quantum magnets was predicted almost 80 years ago. Identifying signatures of magnon bound states has so far remained the subject of intense theoretical research, and their detection has proved challenging for experiments. Ultracold atoms offer an ideal setting in which to find such bound states by tracking the spin dynamics with single-spin and single-site resolution following a local excitation. Here we use in situ correlation measurements to observe two-magnon bound states directly in a one-dimensional Heisenberg spin chain comprising ultracold bosonic atoms in an optical lattice. We observe the quantum dynamics of free and bound magnon states through time-resolved measurements of two spin impurities. The increased effective mass of the compound magnon state results in slower spin dynamics as compared to single-magnon excitations. We also determine the decay time of bound magnons, which is probably limited by scattering on thermal fluctuations in the system. Our results provide a new way of studying fundamental properties of quantum magnets and, more generally, properties of interacting impurities in quantum many-body systems.

Multi-scale modeling to relate Be surface temperatures, concentrations and molecular sputtering yields

NASA Astrophysics Data System (ADS)

Lasa, Ane; Safi, Elnaz; Nordlund, Kai

2015-11-01

Recent experiments and Molecular Dynamics (MD) simulations show erosion rates of Be exposed to deuterium (D) plasma varying with surface temperature and the correlated D concentration. Little is understood how these three parameters relate for Be surfaces, despite being essential for reliable prediction of impurity transport and plasma facing material lifetime in current (JET) and future (ITER) devices. A multi-scale exercise is presented here to relate Be surface temperatures, concentrations and sputtering yields. Kinetic Monte Carlo (MC) code MMonCa is used to estimate equilibrium D concentrations in Be at different temperatures. Then, mixed Be-D surfaces - that correspond to the KMC profiles - are generated in MD, to calculate Be-D molecular erosion yields due to D irradiation. With this new database implemented in the 3D MC impurity transport code ERO, modeling scenarios studying wall erosion, such as RF-induced enhanced limiter erosion or main wall surface temperature scans run at JET, can be revisited with higher confidence. Work supported by U.S. DOE under Contract DE-AC05-00OR22725.

Reversed Hall effect and plasma conductivity in the presence of charged impurities

NASA Astrophysics Data System (ADS)

Yaroshenko, V. V.; Lühr, H.

2018-01-01

The Hall conductivity of magnetized plasma can be strongly suppressed by the contribution of negatively charged particulates (referred further as "dust"). Once the charge density accumulated by the dust exceeds a certain threshold, the Hall component becomes negative, providing a reversal in the Hall current. Such an effect is unique for dust-loaded plasmas, and it can hardly be achieved in electronegative plasmas. Further growth of the dust density leads to an increase in both the absolute value of the Hall and Pedersen conductivities, while the field-aligned component is decreased. These modifications enhance the role of transverse electric currents and reduce the anisotropy of a magnetized plasma when loaded with charged impurities. The findings provide an important basis for studying the generation of electric currents and transport phenomena in magnetized plasma systems containing small charged particulates. They can be relevant for a wide range of applications from naturally occurring space plasmas in planetary magnetospheres and astrophysical objects to laboratory dusty plasmas (Magnetized Dusty Plasma Experiment) and to technological and fusion plasmas.

A review of radiative detachment studies in tokamak advanced magnetic divertor configurations

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

Soukhanovskii, V. A.

The present vision for a plasma–material interface in the tokamak is an axisymmetric poloidal magnetic X-point divertor. Four tasks are accomplished by the standard poloidal X-point divertor: plasma power exhaust; particle control (D/T and He pumping); reduction of impurity production (source); and impurity screening by the divertor scrape-off layer. A low-temperature, low heat flux divertor operating regime called radiative detachment is viewed as the main option that addresses these tasks for present and future tokamaks. Advanced magnetic divertor configuration has the capability to modify divertor parallel and cross-field transport, radiative and dissipative losses, and detachment front stability. Advanced magnetic divertormore » configurations are divided into four categories based on their salient qualitative features: (1) multiple standard X-point divertors; (2) divertors with higher order nulls; (3) divertors with multiple X-points; and (4) long poloidal leg divertors (and also with multiple X-points). As a result, this paper reviews experiments and modeling in the area of radiative detachment in the advanced magnetic divertor configurations.« less

Removal of fluoride, arsenic and coliform bacteria by modified homemade filter media from drinking water.

PubMed

Devi, Rani; Alemayehu, Esayas; Singh, Vijender; Kumar, Ashok; Mengistie, Embialle

2008-05-01

An attempt was made to investigate the removal of fluoride, arsenic and coliform bacteria from drinking water using modified homemade filter media. Batch mode experimental study was conducted to test the efficiency of modified homemade filter for reduction of impurities under the operating condition of treatment time. The physico-chemical and biological analysis of water samples had been done before and after the treatment with filter media, using standard methods. Optimum operating treatment time was determined for maximum removal of these impurities by running the experiment for 2, 4, 6, 8, 10 and 12h, respectively. The maximum reduction of fluoride, arsenic and coliform bacteria in percentage was 85.60%, 93.07% and 100% and their residual values were 0.72 mg/l, 0.009 mg/l and 0 coliform cells/100ml, respectively after a treatment time of 10h. These residual values were under the permissible limits prescribed by WHO. Hence this could be a cheap, easy and an efficient technique for removal of fluoride, arsenic and coliform bacteria from drinking water.

Quantitative determination of salbutamol sulfate impurities using achiral supercritical fluid chromatography.

PubMed

Dispas, Amandine; Desfontaine, Vincent; Andri, Bertyl; Lebrun, Pierre; Kotoni, Dorina; Clarke, Adrian; Guillarme, Davy; Hubert, Philippe

2017-02-05

In the last years, supercritical fluid chromatography has largely been acknowledged as a singular and performing technique in the field of separation sciences. Recent studies highlighted the interest of SFC for the quality control of pharmaceuticals, especially in the case of the determination of the active pharmaceutical ingredient (API). Nevertheless, quality control requires also the determination of impurities. The objectives of the present work were to (i) demonstrate the interest of SFC as a reference technique for the determination of impurities in salbutamol sulfate API and (ii) to propose an alternative to a reference HPLC method from the European Pharmacopeia (EP) involving ion-pairing reagent. Firstly, a screening was carried out to select the most adequate and selective stationary phase. Secondly, in the context of robust optimization strategy, the method was developed using design space methodology. The separation of salbutamol sulfate and related impurities was achieved in 7min, which is seven times faster than the LC-UV method proposed by European Pharmacopeia (total run time of 50min). Finally, full validation using accuracy profile approach was successfully achieved for the determination of impurities B, D, F and G in salbutamol sulfate raw material. The validated dosing range covered 50 to 150% of the targeted concentration (corresponding to 0.3% concentration level), LODs close to 0.5μg/mL were estimated. The SFC method proposed in this study could be presented as a suitable fast alternative to EP LC method for the quantitative determination of salbutamol impurities. Copyright © 2016 Elsevier B.V. All rights reserved.

Isolation, structural determination, synthesis and quantitative determination of impurities in Intron-A, leached from a silicone tubing.

PubMed

Chan, Tze-Ming; Pramanik, Birendra; Aslanian, Robert; Gullo, Vincent; Patel, Mahesh; Cronin, Bart; Boyce, Chris; McCormick, Kevin; Berlin, Mike; Zhu, Xiaohong; Buevich, Alexei; Heimark, Larry; Bartner, Peter; Chen, Guodong; Pu, Haiyan; Hegde, Vinod

2009-02-20

Investigation of unexpected levels of impurities in Intron product has revealed the presence of low levels of impurities leached from the silicone tubing (Rehau RAU-SIK) on the Bosch filling line. In order to investigate the effect of these compounds (1a, 1b and 2) on humans, they were isolated identified and synthesized. They were extracted from the tubing by stirring in Intron placebo at room temperature for 72 h and were enriched on a reverse phase CHP-20P column, eluting with gradient aqueous ACN and were separated by HPLC. Structural elucidation of 1a, 1b and 2 by MS and NMR studies demonstrated them to be halogenated biphenyl carboxylic acids. The structures were confirmed by independent synthesis. Levels of extractable impurities in first filled vials of actual production are estimated to be in the range of 0.01-0.55 microg/vial for each leached impurity. Potential toxicity of these extractables does not represent a risk for patients under the conditions of clinical use.

Role of four-fermion interaction and impurity in the states of two-dimensional semi-Dirac materials.

PubMed

Wang, Jing

2018-03-28

We study the effects of four-fermion interaction and impurity on the low-energy states of 2D semi-Dirac materials by virtue of the unbiased renormalization group approach. The coupled flow equations that govern the energy-dependent evolutions of all correlated interaction parameters are derived after taking into account one-loop corrections from the interplay between four-fermion interaction and impurity. Whether and how four-fermion interaction and impurity influence the low-energy properties of 2D semi-Dirac materials are discreetly explored and addressed attentively. After carrying out the standard renormalization group analysis, we find that both trivial insulating and nontrivial semimetal states are qualitatively stable against all four kinds of four-fermion interactions. However, while switching on both four-fermion interaction and impurity, certain insulator-semimetal phase transitions and the distance of Dirac nodal points can be respectively induced and modified due to their strong interplay and intimate competition. Moreover, several non-Fermi liquid behaviors that deviate from the conventional Fermi liquids are exhibited at the lowest-energy limit.

Bose polaronic soliton-molecule and vector solitons in PT -symmetric potential

NASA Astrophysics Data System (ADS)

Boudjemâa, Abdelâali

2017-07-01

We study analytically and numerically the properties of polaronic soliton molecules and vector solitons of a trapped Bose-Einstein condensate (BEC)-impurity mixture subjected to a PT -symmetric potential in a quasi one-dimensional geometry employing our time-dependent Hartree-Fock-Bogoliubov equations. Analytical results, based on a variational approach and checked with direct numerical simulations reveal that the width, chirp, the vibration frequency and the profile of impurity solitons are enhanced by varying the strengths of real and imaginary parts of PT -symmetric potential as well as the boson-boson and boson-impurity interaction. We address the impact of the imaginary part of the potential, which represents a gain-loss mechanism, on the dynamics and on the stability of the impurity soliton-molecule. We show that for sufficiently strong complex part of the potential, the single soliton exhibits a snake instability and the molecule destroys analogous to the dissociation of a diatomic molecule. We discuss, on the other hand, the formation of several unusual families of three-component vector solitons in the BEC-impurity mixture. An unconventional dark (D)-bright (B) soliton conversion is found.

Effect of atomic disorder on the magnetic phase separation.

PubMed

Groshev, A G; Arzhnikov, A K

2018-05-10

The effect of disorder on the magnetic phase separation between the antiferromagnetic and incommensurate helical [Formula: see text] and [Formula: see text] phases is investigated. The study is based on the quasi-two-dimensional single-band Hubbard model in the presence of atomic disorder (the [Formula: see text] Anderson-Hubbard model). A model of binary alloy disorder is considered, in which the disorder is determined by the difference in energy between the host and impurity atomic levels at a fixed impurity concentration. The problem is solved within the theory of functional integration in static approximation. Magnetic phase diagrams are obtained as functions of the temperature, the number of electrons and impurity concentration with allowance for phase separation. It is shown that for the model parameters chosen, the disorder caused by impurities whose atomic-level energy is greater than that of the host atomic levels, leads to qualitative changes in the phase diagram of the impurity-free system. In the opposite case, only quantitative changes occur. The peculiarities of the effect of disorder on the phase separation regions of the quasi-two-dimensional Hubbard model are discussed.

High-frequency EPR of surface impurities on nanodiamond

NASA Astrophysics Data System (ADS)

Peng, Zaili; Stepanov, Viktor; Takahashi, Susumu

Diamond is a fascinating material, hosting nitrogen-vacancy (NV) defect centers with unique magnetic and optical properties. There have been many reports that suggest the existence of paramagnetic impurities near surface of various kinds of diamonds. Electron paramagnetic resonance (EPR) investigation of mechanically crushed nanodiamonds (NDs) as well as detonation NDs revealed g 2 like signals that are attributed to structural defects and dangling bonds near the diamond surface. In this presentation, we investigate paramagnetic impurities in various sizes of NDs using high-frequency (HF) continuous wave (cw) and pulsed EPR spectroscopy. Strong size dependence on the linewidth of HF cw EPR spectra reveals the existence of paramagnetic impurities in the vicinity of the diamond surface. We also study the size dependence of the spin-lattice and spin-spin relaxation times (T1 and T2) of single substitutional nitrogen defects in NDs Significant deviations from the temperature dependence of the phonon-assisted T1 process were observed in the ND samples, and were attributed to the contribution from the surface impurities. This work was supported by the Searle Scholars Program and the National Science Foundation (DMR-1508661 and CHE-1611134).

Impurity-induced anisotropic semiconductor-semimetal transition in monolayer biased black phosphorus

NASA Astrophysics Data System (ADS)

Bui, D. H.; Yarmohammadi, Mohsen

2018-07-01

Taking into account the electron-impurity interaction within the continuum approximation of tight-binding model, the Born approximation, and the Green's function method, the main features of anisotropic electronic phase transition are investigated in monolayer biased black phosphorus (BP). To this end, we concentrated on the disordered electronic density of states (DOS), which gives useful information for electro-optical devices. Increasing the impurity concentration in both unbiased and biased impurity-infected single-layer BP, in addition to the decrease of the band gap, independent of the direction, leads to the midgap states and an extra Van Hove singularity inside and outside of the band gap, respectively. Furthermore, strong impurity scattering potentials lead to a semiconductor-semimetal transition and one more Van Hove singularity in x-direction of unbiased BP and surprisingly, this transition does not occur in biased BP. We found that there is no phase transition in y-direction. Since real applications require structures with modulated band gaps, we have studied the influence of different bias voltages on the disordered DOS in both directions, resulting in the increase of the band gap.

Effect of atomic disorder on the magnetic phase separation

NASA Astrophysics Data System (ADS)

Groshev, A. G.; Arzhnikov, A. K.

2018-05-01

The effect of disorder on the magnetic phase separation between the antiferromagnetic and incommensurate helical and phases is investigated. The study is based on the quasi-two-dimensional single-band Hubbard model in the presence of atomic disorder (the Anderson–Hubbard model). A model of binary alloy disorder is considered, in which the disorder is determined by the difference in energy between the host and impurity atomic levels at a fixed impurity concentration. The problem is solved within the theory of functional integration in static approximation. Magnetic phase diagrams are obtained as functions of the temperature, the number of electrons and impurity concentration with allowance for phase separation. It is shown that for the model parameters chosen, the disorder caused by impurities whose atomic-level energy is greater than that of the host atomic levels, leads to qualitative changes in the phase diagram of the impurity-free system. In the opposite case, only quantitative changes occur. The peculiarities of the effect of disorder on the phase separation regions of the quasi-two-dimensional Hubbard model are discussed.

Role of four-fermion interaction and impurity in the states of two-dimensional semi-Dirac materials

NASA Astrophysics Data System (ADS)

Wang, Jing

2018-03-01

We study the effects of four-fermion interaction and impurity on the low-energy states of 2D semi-Dirac materials by virtue of the unbiased renormalization group approach. The coupled flow equations that govern the energy-dependent evolutions of all correlated interaction parameters are derived after taking into account one-loop corrections from the interplay between four-fermion interaction and impurity. Whether and how four-fermion interaction and impurity influence the low-energy properties of 2D semi-Dirac materials are discreetly explored and addressed attentively. After carrying out the standard renormalization group analysis, we find that both trivial insulating and nontrivial semimetal states are qualitatively stable against all four kinds of four-fermion interactions. However, while switching on both four-fermion interaction and impurity, certain insulator-semimetal phase transitions and the distance of Dirac nodal points can be respectively induced and modified due to their strong interplay and intimate competition. Moreover, several non-Fermi liquid behaviors that deviate from the conventional Fermi liquids are exhibited at the lowest-energy limit.

Impact of centrifugal drifts on ion turbulent transport

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

Belli, Emily A.; Candy, J.

Here, the influence of sonic toroidal rotation on gyrokinetic stability and transport is studied, with important implications for heavy impurity dynamics. When centrifugal drifts and electrostatic trapping corrections are included, significant modifications to the calculated transport of heavy impurities are observed. These high-rotation corrections add to the standard Coriolis drift and toroidal rotation shear drive which are normally included in gyrokinetics. Yet, because of their complexity, centrifugal and electrostatic trapping terms (quadratic in the main ion Mach number) are not generally included in gyrokinetic codes. In this work, we explore the implications of using reduced descriptions of the rotational physics.more » For heavy impurities such as tungsten, cross terms due to the centrifugal force can dominate the rotation dynamics, and neglecting them is shown to lead to large errors in the impurity particle flux.« less

Impact of centrifugal drifts on ion turbulent transport

DOE PAGES

Belli, Emily A.; Candy, J.

2018-03-01

Here, the influence of sonic toroidal rotation on gyrokinetic stability and transport is studied, with important implications for heavy impurity dynamics. When centrifugal drifts and electrostatic trapping corrections are included, significant modifications to the calculated transport of heavy impurities are observed. These high-rotation corrections add to the standard Coriolis drift and toroidal rotation shear drive which are normally included in gyrokinetics. Yet, because of their complexity, centrifugal and electrostatic trapping terms (quadratic in the main ion Mach number) are not generally included in gyrokinetic codes. In this work, we explore the implications of using reduced descriptions of the rotational physics.more » For heavy impurities such as tungsten, cross terms due to the centrifugal force can dominate the rotation dynamics, and neglecting them is shown to lead to large errors in the impurity particle flux.« less

Water Oxidation Catalysis by Co(II) Impurities in Co(III) 4O 4 Cubanes

DOE PAGES

Ullman, Andrew M.; Liu, Yi; Huynh, Michael; ...

2014-11-18

Here, the observed water oxidation activity of the compound class Co 4O 4(OAc) 4(Py–X) 4 emanates from a Co(II) impurity. This impurity is oxidized to produce the well-known Co-OEC heterogeneous cobaltate catalyst, which is an active water oxidation catalyst. We present results from electron paramagnetic resonance spectroscopy, nuclear magnetic resonance line broadening analysis, and electrochemical titrations to establish the existence of the Co(II) impurity as the major source of water oxidation activity that has been reported for Co 4O 4 molecular cubanes. Differential electrochemical mass spectrometry is used to characterize the fate of glassy carbon at water oxidizing potentials andmore » demonstrate that such electrode materials should be used with caution for the study of water oxidation catalysis.« less

Precise impurity analysis of Cu films by GDMS: relation between negative substrate bias voltage and impurity ionization potentials

NASA Astrophysics Data System (ADS)

Lim, J. W.; Mimura, K.; Isshiki, M.

2005-02-01

Cu films were deposited on Si(100) substrates by applying a negative substrate bias voltage using the non-mass-separated ion beam deposition method. Glow-discharge mass spectrometry was used to determine the impurity concentrations of the deposited Cu films and the 6N Cu target. It was found that the Cu film deposited at the substrate bias voltage of -50 V showed lower impurity contents than the Cu film deposited without the substrate bias voltage, although both the Cu films were contaminated during the deposition. The purification effect might result from the following reasons: (i) the Penning ionization and an ionization mechanism proposed in the present study, (ii) a difference in the kinetic energy of accelerated Cu+ ions toward the substrate with/without the negative substrate bias voltage.

Stability-indicating HPLC-DAD/UV-ESI/MS impurity profiling of the anti-malarial drug lumefantrine.

PubMed

Verbeken, Mathieu; Suleman, Sultan; Baert, Bram; Vangheluwe, Elien; Van Dorpe, Sylvia; Burvenich, Christian; Duchateau, Luc; Jansen, Frans H; De Spiegeleer, Bart

2011-02-28

Lumefantrine (benflumetol) is a fluorene derivative belonging to the aryl amino alcohol class of anti-malarial drugs and is commercially available in fixed combination products with β-artemether. Impurity characterization of such drugs, which are widely consumed in tropical countries for malaria control programmes, is of paramount importance. However, until now, no exhaustive impurity profile of lumefantrine has been established, encompassing process-related and degradation impurities in active pharmaceutical ingredients (APIs) and finished pharmaceutical products (FPPs). Using HPLC-DAD/UV-ESI/ion trap/MS, a comprehensive impurity profile was established based upon analysis of market samples as well as stress, accelerated and long-term stability results. In-silico toxicological predictions for these lumefantrine related impurities were made using Toxtree® and Derek®. Several new impurities are identified, of which the desbenzylketo derivative (DBK) is proposed as a new specified degradant. DBK and the remaining unspecified lumefantrine related impurities are predicted, using Toxtree® and Derek®, to have a toxicity risk comparable to the toxicity risk of the API lumefantrine itself. From unstressed, stressed and accelerated stability samples of lumefantrine API and FPPs, nine compounds were detected and characterized to be lumefantrine related impurities. One new lumefantrine related compound, DBK, was identified and characterized as a specified degradation impurity of lumefantrine in real market samples (FPPs). The in-silico toxicological investigation (Toxtree® and Derek®) indicated overall a toxicity risk for lumefantrine related impurities comparable to that of the API lumefantrine itself.

Evaluating and modeling the effects of surface sampling factors on the recovery of organic chemical attribution signatures using the accelerated diffusion sampler and solvent extraction

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

Mo, Kai-For; Heredia-Langner, Alejandro; Fraga, Carlos G.

In this study, an experimental design matrix was created and executed in order to test the effects of various real-world factors on the ability of the (1) accelerated diffusion sampler with solid phase micro-extraction (ADS-SPME) and (2) solvent extraction to capture organic chemical attribution signatures (CAS) from dimethyl methylphosphonate (DMMP) spiked onto painted wall board (PWB) surfaces. The DMMP CAS organic impurities sampled by ADS-SPME and solvent extraction were analyzed by gas chromatography/mass spectrometry (GC/MS). The number of detected DMMP CAS impurities and their respective GC/MS peak areas were determined as a function of DMMP stock, DMMP spiked volume, exposuremore » time, SPME sampling time, and ADS headspace pressure. Based on the statistical analysis of experimental results, several general conclusions are made: (1) ADS-SPME with vacuum (i.e., reduced pressure) increased the amount of detected CAS impurity, as measured by GC/MS peak area, by a factor of 1.7 to 1.9 for PWB under certain experimental conditions, (2) the amount of detected CAS impurity was most influenced by spiked volume, stock, and ADS headspace pressure, (3) the ADS had no measurable effect on the number of detected DMMP impurities, that is, the ADS (with and without reduced pressure) had no practical effect on the DMMP impurity profile collected from spiked PWB, and (4) solvent extraction out performed ADS-SPME in terms of consistently capturing all or most of the targeted DMMP impurities from spiked PWB.« less

Depinning of the transverse domain wall trapped at magnetic impurities patterned in planar nanowires: Control of the wall motion using low-intensity and short-duration current pulses

NASA Astrophysics Data System (ADS)

Paixão, E. L. M.; Toscano, D.; Gomes, J. C. S.; Monteiro, M. G.; Sato, F.; Leonel, S. A.; Coura, P. Z.

2018-04-01

Understanding and controlling of domain wall motion in magnetic nanowires is extremely important for the development and production of many spintronic devices. It is well known that notches are able to pin domain walls, but their pinning potential strength are too strong and it demands high-intensity current pulses to achieve wall depinning in magnetic nanowires. However, traps of pinning can be also originated from magnetic impurities, consisting of located variations of the nanowire's magnetic properties, such as exchange stiffness constant, saturation magnetization, anisotropy constant, damping parameter, and so on. In this work, we have performed micromagnetic simulations to investigate the depinning mechanism of a transverse domain wall (TDW) trapped at an artificial magnetic defect using spin-polarized current pulses. In order to create pinning traps, a simplified magnetic impurity model, only based on a local reduction of the exchange stiffness constant, have been considered. In order to provide a background for experimental studies, we have varied the parameter related to the pinning potential strength of the magnetic impurity. By adjusting the pinning potential of magnetic impurities and choosing simultaneously a suitable current pulse, we have found that it is possible to obtain domain wall depinning by applying low-intensity and short-duration current pulses. Furthermore, it was considered a planar magnetic nanowire containing a linear distribution of equally-spaced magnetic impurities and we have demonstrated the position control of a single TDW by applying sequential current pulses; that means the wall movement from an impurity to another.

Evaluating and modeling the effects of surface sampling factors on the recovery of organic chemical attribution signatures using the accelerated diffusion sampler and solvent extraction.

PubMed

Mo, Kai-For; Heredia-Langner, Alejandro; Fraga, Carlos G

2017-03-01

In this study, an experimental design matrix was created and executed to test the effects of various real-world factors on the ability of (1) the accelerated diffusion sampler with solid phase micro-extraction (ADS-SPME) and (2) solvent extraction to capture organic chemical attribution signatures (CAS) from dimethyl methylphosphonate (DMMP) spiked onto painted wall board (PWB) surfaces. The DMMP CAS organic impurities sampled by ADS-SPME and solvent extraction were analyzed by gas chromatography/mass spectrometry (GC/MS). The number of detected DMMP CAS impurities and their respective GC/MS peak areas were determined as a function of DMMP stock, DMMP spiked volume, exposure time, SPME sampling time, and ADS headspace pressure. Based on the statistical analysis of experimental results, several general conclusions are made: (1) the amount of CAS impurity detected using ADS-SPME and GC/MS was most influenced by spiked volume, stock, and ADS headspace pressure, (2) reduced ADS headspace pressure increased the amount of detected CAS impurity, as measured by GC/MS peak area, by up to a factor of 1.7-1.9 compared to ADS at ambient headspace pressure, (3) the ADS had no measurable effect on the number of detected DMMP impurities, that is, ADS (with and without reduced pressure) had no practical effect on the DMMP impurity profile collected from spiked PWB, and (4) solvent extraction out performed ADS-SPME in terms of consistently capturing all or most of the targeted DMMP impurities from spiked PWB. Copyright © 2016 Elsevier B.V. All rights reserved.

Study on gamma and electron beam sterilization of third generation cephalosporins cefdinir and cefixime in solid state

NASA Astrophysics Data System (ADS)

Singh, Babita K.; Parwate, Dilip V.; Das Sarma, Indrani B.; Shukla, Sudhir K.

2010-10-01

The effect of gamma radiation from 60Co source and 2 MeV e-beam was studied on two thermolabile cephalosporin antibiotics viz cefdinir and cefixime in solid state. The parameters studied to assess radiolytic degradation were loss of chemical and microbiological potency, change in optical rotation, electronic and vibrational absorption characteristics, thermal behavior and color modification. ESR spectroscopic study, HPLC related impurity profile, thermogram and Raman spectrum are applied in deducing the nature of radiolytic impurities and their formation hypotheses. Cefixime is radiation sensitive, whereas cefdinir has acceptable radiation resistance at 25 kGy dose. The nature of radiolytic related impurities and their concentrations indicates that the lactam ring is not highly susceptible to direct radiation attack, which otherwise is considered very sensitive to stress (thermal, chemical and photochemical).

Numerical Characterization of Wall Recycling Conditions of the HIDRA Stellarator using EMC3-EIRENE

NASA Astrophysics Data System (ADS)

Marcinko, Steven; Curreli, Davide

2015-11-01

The wall recycling conditions created by energetic bombardment of plasma-facing components (PFCs) are of critical importance to determining the plasma and impurity profile in the edge region of a magnetically confined plasma. In this work a pre-online numerical characterization of the edge plasma in HIDRA has been carried out. HIDRA is the former WEGA experiment, now relocated to the University of Illinois at Urbana-Champaign. Numerical simulations of the HIDRA edge environment are performed utilizing the 3D edge plasma and neutral transport code EMC3-EIRENE [Y. Feng J. Nucl. Mater 241-243, 930 (1997)]. In our analysis, emphasis is placed on the influence of the neutrals and the impurities on edge plasma profiles and thus on energy and particle fluxes impingent onto PFCs. We examine the effect of different wall types, comparing high recycling conditions to situations of low recycling. The effect of intrinsic impurity screening is also taken into account under the expected HIDRA operating regimes. We report the calculated particle confinement time and fluid moments of both plasma and neutrals at the low recycling regimes expected with lithium-based PFCs, and compare them with the high recycling regimes found with conventional metal-based PFCs.

Confined ion energy >200 keV and increased fusion yield in a DPF with monolithic tungsten electrodes and pre-ionization

NASA Astrophysics Data System (ADS)

Lerner, Eric J.; Hassan, Syed M.; Karamitsos, Ivana; Von Roessel, Fred

2017-10-01

To reduce impurities in the dense plasma focus FF-1 device, we used monolithic tungsten electrodes with pre-ionization. With this new set-up, we demonstrated a three-fold reduction of impurities by mass and a ten-fold reduction by ion number. FF-1 produced a 50% increase in fusion yield over our previous copper electrodes, both for a single shot and for a mean of ten consecutive shots with the same conditions. These results represent a doubling of fusion yield as compared with any other plasma focus device with the same 60 kJ energy input. In addition, FF-1 produced a new single-shot record of 240 ± 20 keV for mean ion energy, a record for any confined fusion plasma, using any device, and a 50% improvement in ten-shot mean ion energy. With a deuterium-nitrogen mix and corona-discharge pre-ionization, we were also able to reduce the standard deviation in the fusion yield to about 15%, a four-fold reduction over the copper-electrode results. We intend to further reduce impurities with new experiments using microwave treatment of tungsten electrodes, followed by the use of beryllium electrodes.

High Performance Double-null Plasma Operation Under Radiating Divertor Conditions

NASA Astrophysics Data System (ADS)

Petrie, T. W.; Osborne, T.; Leonard, A. W.; Luce, T. C.; Petty, C. C.; Fenstermacher, M. E.; Lasnier, C. J.; Turco, F.; Watkins, J. G.

2017-10-01

We report on heat flux reduction experiments in which deuterium/neon- or deuterium/argon-based radiating mantle/divertor approaches were applied to high performance double-null (DN) plasmas (H98 1.4-1.7,βN 4 , q 95 6) with a combined neutral beam and ECH power input PIN 15 MW. When the radial location of the ECH deposition is close to the magnetic axis (e.g., ρ <=0.20), the radial profiles of both injected and intrinsic impurities are flat to somewhat hollow. For deposition farther out (e.g., ρ=0.45), the impurity profiles are highly peaked on axis, which would make high performance DN operation with impurity injection more problematical. Comparison of neon with argon `seeding' with respect to core dilution, energy confinement, and heat flux reduction under these conditions favors argon. Conditions that lead to an improved τE as predicted previously from ELITE code analysis, i.e., very high PIN, proximity to magnetic balance, and higher q95, are largely consistent with this data. Work was supported by the US DOE under DE-FC02-04ER54698, DE-AC52-07NA27344, DE-FG02-04ER54761, and DE-AC04-94AL85000.

Nonlinear Burn Control and Operating Point Optimization in ITER

NASA Astrophysics Data System (ADS)

Boyer, Mark; Schuster, Eugenio

2013-10-01

Control of the fusion power through regulation of the plasma density and temperature will be essential for achieving and maintaining desired operating points in fusion reactors and burning plasma experiments like ITER. In this work, a volume averaged model for the evolution of the density of energy, deuterium and tritium fuel ions, alpha-particles, and impurity ions is used to synthesize a multi-input multi-output nonlinear feedback controller for stabilizing and modulating the burn condition. Adaptive control techniques are used to account for uncertainty in model parameters, including particle confinement times and recycling rates. The control approach makes use of the different possible methods for altering the fusion power, including adjusting the temperature through auxiliary heating, modulating the density and isotopic mix through fueling, and altering the impurity density through impurity injection. Furthermore, a model-based optimization scheme is proposed to drive the system as close as possible to desired fusion power and temperature references. Constraints are considered in the optimization scheme to ensure that, for example, density and beta limits are avoided, and that optimal operation is achieved even when actuators reach saturation. Supported by the NSF CAREER award program (ECCS-0645086).

Nature of impurities in fertilizers containing EDDHMA/Fe(3+), EDDHSA/Fe(3+), and EDDCHA/Fe(3+) chelates.

PubMed

Alvarez-Fernández, Ana; Cremonini, Mauro A; Sierra, Miguel A; Placucci, Giuseppe; Lucena, Juan J

2002-01-16

Iron chelates derived from ethylenediaminedi(o-hydroxyphenylacetic) acid (EDDHA), ethylenediaminedi(o-hydroxy-p-methylphenylacetic) acid (EDDHMA), ethylenediaminedi(2-hydroxy-5-sulfophenylacetic) acid (EDDHSA), and ethylenediaminedi(5-carboxy-2-hydroxyphenylacetic) acid (EDDCHA) are remarkably efficient in correcting iron chlorosis in plants growing in alkaline soils. This work reports the determination of impurities in commercial samples of fertilizers containing EDDHMA/Fe(3+), EDDHSA/Fe(3+), and EDDCHA/Fe(3+). The active components (EDDHMA/Fe(3+), EDDHSA/Fe(3+), and EDDCHA/Fe(3+)) were separated easily from other compounds present in the fertilizers by HPLC. Comparison of the retention times and the UV-visible spectra of the peaks obtained from commercial EDDHSA/Fe(3+) and EDDCHA/Fe(3+) samples with those of standard solutions showed that unreacted starting materials (p-hydroxybenzenesulfonic acid and p-hydroxybenzoic acid, respectively) were always present in the commercial products. 1D and 2D NMR experiments showed that commercial fertilizers based on EDDHMA/Fe(3+) contained impurities having structures tentatively assigned to iron chelates of two isomers of EDDHMA. These findings suggest that current production processes of iron chelates used in agriculture need to be improved.

Impurity-induced moments in underdoped cuprates

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

Khaliullin, G.; Kilian, R.; Krivenko, S.

1997-11-01

We examine the effect of a nonmagnetic impurity in a two-dimensional spin liquid in the spin-gap phase, employing a drone-fermion representation of spin-1/2 operators. The properties of the local moment induced in the vicinity of the impurity are investigated and an expression for the nuclear-magnetic-resonance Knight shift is derived, which we compare with experimental results. Introducing a second impurity into the spin liquid an antiferromagnetic interaction between the moments is found when the two impurities are located on different sublattices. The presence of many impurities leads to a screening of this interaction as is shown by means of a coherent-potentialmore » approximation. Further, the Kondo screening of an impurity-induced local spin by charge carriers is discussed. {copyright} {ital 1997} {ital The American Physical Society}« less

Impurity doping effects on the orbital thermodynamic properties of hydrogenated graphene, graphane, in Harrison model

NASA Astrophysics Data System (ADS)

Yarmohammadi, Mohsen

2016-12-01

Using the Harrison model and Green's function technique, impurity doping effects on the orbital density of states (DOS), electronic heat capacity (EHC) and magnetic susceptibility (MS) of a monolayer hydrogenated graphene, chair-like graphane, are investigated. The effect of scattering between electrons and dilute charged impurities is discussed in terms of the self-consistent Born approximation. Our results show that the graphane is a semiconductor and its band gap decreases with impurity. As a remarkable point, comparatively EHC reaches almost linearly to Schottky anomaly and does not change at low temperatures in the presence of impurity. Generally, EHC and MS increases with impurity doping. Surprisingly, impurity doping only affects the salient behavior of py orbital contribution of carbon atoms due to the symmetry breaking.

U-series dating of impure carbonates: An isochron technique using total-sample dissolution

USGS Publications Warehouse

Bischoff, J.L.; Fitzpatrick, J.A.

1991-01-01

U-series dating is a well-established technique for age determination of Late Quaternary carbonates. Materials of sufficient purity for nominal dating, however, are not as common as materials with mechanically inseparable aluminosilicate detritus. Detritus contaminates the sample with extraneous Th. We propose that correction for contamination is best accomplished with the isochron technique using total sample dissolution (TSD). Experiments were conducted on artificial mixtures of natural detritus and carbonate and on an impure carbonate of known age. Results show that significant and unpredictable transfer of radionuclides occur from the detritus to the leachate in commonly used selective leaching procedures. The effects of correcting via leachate-residue pairs and isochron plots were assessed. Isochrons using TSD gave best results, followed by isochron plots of leachates only. ?? 1991.

Conductivity of Weakly Disordered Metals Close to a "Ferromagnetic" Quantum Critical Point

NASA Astrophysics Data System (ADS)

Kastrinakis, George

2018-05-01

We calculate analytically the conductivity of weakly disordered metals close to a "ferromagnetic" quantum critical point in the low-temperature regime. Ferromagnetic in the sense that the effective carrier potential V(q,ω ), due to critical fluctuations, is peaked at zero momentum q=0. Vertex corrections, due to both critical fluctuations and impurity scattering, are explicitly considered. We find that only the vertex corrections due to impurity scattering, combined with the self-energy, generate appreciable effects as a function of the temperature T and the control parameter a, which measures the proximity to the critical point. Our results are consistent with resistivity experiments in several materials displaying typical Fermi liquid behaviour, but with a diverging prefactor of the T^2 term for small a.

A new approach to design safe CNTs with an understanding of redox potential.

PubMed

Tsuruoka, Shuji; Cassee, Flemming R; Castranova, Vincent

2013-09-02

Carbon nanotubes (CNTs) are being increasingly industrialized and applied for various products. As of today, although several toxicological evaluations of CNTs have been conducted, designing safer CNTs is not practiced because reaction kinetics of CNTs with bioactive species is not fully understood. The authors propose a kinetic mechanism to establish designing safe CNTs as a new goal. According to a literature search on the behavior of CNTs and the effects of impurities, it is found that chemical reactions on CNT surface are attributed to redox reactions involving metal impurities and carbon structures at the CNT surface. A new goal is proposed to design safer CNTs using the redox potential hypothesis. The value of this hypothesis must be practically investigated and proven through the further experiments.

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

Fraga, Carlos G.; Sego, Landon H.; Hoggard, Jamin C.

Dimethyl methylphosphonate (DMMP) was used as a chemical threat agent (CTA) simulant for a first look at the effects of real-world factors on the recovery and exploitation of a CTA’s impurity profile for source matching. Four stocks of DMMP having different impurity profiles were disseminated as aerosols onto cotton, painted wall board, and nylon coupons according to a thorough experimental design. The DMMP-exposed coupons were then solvent extracted and analyzed for DMMP impurities by comprehensive 2-D gas chromatography/mass spectrometry (GC×GC/MS). The similarities between the coupon DMMP impurity profiles and the known (reference) DMMP profiles were measured by dot products ofmore » the coupon profiles and known profiles and by score values obtained from principal component analysis. One stock, with a high impurity-profile selectivity value of 0.9 out of 1, had 100% of its respective coupons correctly classified and no false positives from other coupons. Coupons from the other three stocks with low selectivity values (0.0073, 0.012, and 0.018) could not be sufficiently distinguished from one another for reliable matching to their respective stocks. The results from this work support that: (1) extraction solvents, if not appropriately selected, can have some of the same impurities present in a CTA reducing a CTA’s useable impurity profile, (2) low selectivity among a CTA’s known impurity profiles will likely make definitive source matching impossible in some real-world conditions, (3) no detrimental chemical-matrix interference was encountered during the analysis of actual office media, (4) a short elapsed time between release and sample storage is advantageous for the recovery of the impurity profile because it minimizes volatilization of forensic impurities, and (5) forensic impurity profiles weighted towards higher volatility impurities are more likely to be altered by volatilization following CTA exposure.« less

Turbulent Flame Speeds and NOx Kinetics of HHC Fuels with Contaminants and High Dilution Levels

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

Peterson, Eric; Krejci, Michael; Mathieu, Olivier

2014-01-24

This final report documents the technical results of the 3-year project entitled, “Turbulent Flame Speeds and NOx Kinetics of HHC Fuels with Contaminants and High Dilution Levels,” funded under the NETL of DOE. The research was conducted under six main tasks: 1) program management and planning; 2) turbulent flame speed measurements of syngas mixtures; 3) laminar flame speed measurements with diluents; 4) NOx mechanism validation experiments; 5) fundamental NOx kinetics; and 6) the effect of impurities on NOx kinetics. Experiments were performed using primary constant-volume vessels for laminar and turbulent flame speeds and shock tubes for ignition delay times andmore » species concentrations. In addition to the existing shock- tube and flame speed facilities, a new capability in measuring turbulent flame speeds was developed under this grant. Other highlights include an improved NOx kinetics mechanism; a database on syngas blends for real fuel mixtures with and without impurities; an improved hydrogen sulfide mechanism; an improved ammonia kintics mechanism; laminar flame speed data at high pressures with water addition; and the development of an inexpensive absorption spectroscopy diagnostic for shock-tube measurements of OH time histories. The Project Results for this work can be divided into 13 major sections, which form the basis of this report. These 13 topics are divided into the five areas: 1) laminar flame speeds; 2) Nitrogen Oxide and Ammonia chemical kinetics; 3) syngas impurities chemical kinetics; 4) turbulent flame speeds; and 5) OH absorption measurements for chemical kinetics.« less

Study of the initial transient in the one-dimensional analytical models of impurity segregation during melt crystallization in the presence of convection

NASA Astrophysics Data System (ADS)

Voloshin, A. E.

2013-11-01

The well-known one-dimensional Burton-Prim-Slichter and Ostrogorsky-Müller analytical models obtained for the stationary mass transfer regime describe in a simple form the dependence of the effective impurity segregation coefficient on the ratio of the crystal growth and convective flow rates. Solutions for the initial transient regime are found in both models. It is shown that the formulas obtained make it possible to determine both the crystal growth rate and the convective mixing intensity on the basis of the analysis of impurity segregation in crystal.

DFTB+ and lanthanides

NASA Astrophysics Data System (ADS)

Hourahine, B.; Aradi, B.; Frauenheim, T.

2010-07-01

DFTB+ is a recent general purpose implementation of density-functional based tight binding. One of the early motivators to develop this code was to investigate lanthanide impurities in nitride semiconductors, leading to a series of successful studies into structure and electrical properties of these systems. Here we describe our general framework to treat the physical effects needed for these problematic impurities within a tight-binding formalism, additionally discussing forces and stresses in DFTB. We also present an approach to evaluate the general case of Slater-Koster transforms and all of their derivatives in Cartesian coordinates. These developments are illustrated by simulating isolated Gd impurities in GaN.

Preliminary effects of real-world factors on the recovery and exploitation of forensic impurity profiles of a nerve-agent simulant from office media.

PubMed

Fraga, Carlos G; Sego, Landon H; Hoggard, Jamin C; Acosta, Gabriel A Pérez; Viglino, Emilie A; Wahl, Jon H; Synovec, Robert E

2012-12-28

Dimethyl methylphosphonate (DMMP) was used as a chemical threat agent (CTA) simulant for a first look at the effects of real-world factors on the recovery and exploitation of a CTA's impurity profile for source matching. Four stocks of DMMP having different impurity profiles were disseminated as aerosols onto cotton, painted wall board, and nylon coupons according to a thorough experimental design. The DMMP-exposed coupons were then solvent extracted and analyzed for DMMP impurities by comprehensive 2D gas chromatography/mass spectrometry (GC×GC/MS). The similarities between the coupon DMMP impurity profiles and the known (reference) DMMP profiles were measured by dot products of the coupon profiles and known profiles and by score values obtained from principal component analysis. One stock, with a high impurity-profile selectivity value of 0.9 out of 1, had 100% of its respective coupons correctly classified and no false positives from other coupons. Coupons from the other three stocks with low selectivity values (0.0073, 0.012, and 0.018) could not be sufficiently distinguished from one another for reliable matching to their respective stocks. The results from this work support that: (1) extraction solvents, if not appropriately selected, can have some of the same impurities present in a CTA reducing a CTA's useable impurity profile, (2) low selectivity among a CTA's known impurity profiles will likely make definitive source matching impossible in some real-world conditions, (3) no detrimental chemical-matrix interference was encountered during the analysis of actual office media, (4) a short elapsed time between release and sample storage is advantageous for the recovery of the impurity profile because it minimizes volatilization of forensic impurities, and (5) forensic impurity profiles weighted toward higher volatility impurities are more likely to be altered by volatilization following CTA exposure. Copyright © 2012 Elsevier B.V. All rights reserved.

Assessing the potential impact of non-proprietary drug copies on quality of medicine and treatment in patients with relapsing multiple sclerosis: the experience with fingolimod.

PubMed

Correale, Jorge; Chiquete, Erwin; Milojevic, Snezana; Frider, Nadina; Bajusz, Imre

2014-01-01

Fingolimod is a once-daily oral treatment for relapsing multiple sclerosis, the proprietary production processes of which are tightly controlled, owing to its susceptibility to contamination by impurities, including genotoxic impurities. Many markets produce nonproprietary medicines; assessing their efficacy and safety is difficult as regulators may approve nonproprietary drugs without bioequivalence data, genotoxic evaluation, or risk management plans (RMPs). This assessment is especially important for fingolimod given its solubility/bioavailability profile, genotoxicity risk, and low-dose final product (0.5 mg). This paper presents an evaluation of the quality of proprietary and nonproprietary fingolimod variants. Proprietary fingolimod was used as a reference substance against which eleven nonproprietary fingolimod copies were assessed. The microparticle size distribution of each compound was assessed by laser light diffraction, and inorganic impurity content by sulfated ash testing. Heavy metals content was quantified using inductively coupled plasma optical emission spectrometry, and levels of unspecified impurities by high-performance liquid chromatography. Solubility was assessed in a range of solvents at different pH values. Key information from the fingolimod RMP is also presented. Nonproprietary fingolimod variants exhibited properties out of proprietary or internationally accepted specifications, including differences in particle size distribution and levels of impurities such as heavy metals. For microparticle size and heavy metals, all tested fingolimod copies were out-of-specification by several-fold magnitudes. Proprietary fingolimod has a well-defined RMP, highlighting known and potential mid- to long-term safety risks, and risk-minimization and pharmacovigilance procedures. Nonproprietary fingolimod copies produced by processes less well controlled than or altered from proprietary production processes may reduce product reproducibility and quality, potentially presenting risks to patients. Safety data and risk-minimization strategies for proprietary fingolimod may not apply to the nonproprietary fingolimod copies evaluated here. Market authorization of nonproprietary fingolimod copies should require an appropriate RMP to minimize risks to patients.

NBS (National Bureau of Standards): Materials measurements. [space processing experiments

NASA Technical Reports Server (NTRS)

Manning, J. R.

1983-01-01

Work directed toward the measurement of materials properties important to the design and interpretation of space processing experiments and determinations of how the space environment may offer a unique opportunity for performing improved measurements and producing materials with improved properties is reported. Surface tensions and their variations with temperature and impurities; convection during undirectional solidification; and measurement of the high temperature thermophysical properties of tungsten group liquids and solids are discussed and results are summarized.

Power Radiated from ITER and CIT by Impurities

DOE R&D Accomplishments Database

Cummings, J.; Cohen, S. A.; Hulse, R.; Post, D. E.; Redi, M. H.; Perkins, J.

1990-07-01

The MIST code has been used to model impurity radiation from the edge and core plasmas in ITER and CIT. A broad range of parameters have been varied, including Z{sub eff}, impurity species, impurity transport coefficients, and plasma temperature and density profiles, especially at the edge. For a set of these parameters representative of the baseline ITER ignition scenario, it is seen that impurity radiation, which is produced in roughly equal amounts by the edge and core regions, can make a major improvement in divertor operation without compromising core energy confinement. Scalings of impurity radiation with atomic number and machine size are also discussed.

Combined effects of an intense laser field, electric field and hydrostatic pressure on donor impurity states in zinc-blende InGaN/GaN quantum dots

NASA Astrophysics Data System (ADS)

Wang, Guangxin; Zhou, Rui; Duan, Xiuzhi

2016-07-01

The shallow-donor impurity states in cylindrical zinc-blende (ZB) In x Ga1- x N/GaN quantum dots (QDs) have been theoretically investigated, considering the combined effects of an intense laser field (ILF), an external electric field, and hydrostatic pressure. The numerical results show that for an on-center impurity in ZB In x Ga1- x N/GaN QD, (1) the ground-state binding energy of the donor impurity is a decreasing function of the laser-dressing parameter and/or the QD's height; (2) as the QD's radius decreases, the binding energy of the donor impurity increases at first, reaches a maximum value, and then drops rapidly; (3) the binding energy of the donor impurity is a decreasing function of the external electric field due to the Stark effect; (4) the binding energy of the donor impurity increases as the applied hydrostatic pressure becomes large. In addition, the position of the impurity ion was also found to have an important influence on the binding energy of the donor impurity. The physical reasons have been analyzed in detail.

Clusterization Effects in III-V Nitrides: Nitrogen Vacancies, and Si and Mg Impurities in Aluminum Nitride and Gallium Nitride

NASA Astrophysics Data System (ADS)

Gubanov, V. A.; Pentaleri, E. A.; Boekema, C.; Fong, C. Y.; Klein, B. M.

1997-03-01

We have investigated clusterization of nitrogen vacancies and Si and Mg doping impurities in zinc-blende aluminum nitride (c-AlN) and gallium nitride (c-GaN) by the tight-binding LMTO technique. The calculations used 128-site supercells. Si and Mg atoms replacing ions in both the cation and anion sublattices of the host lattices of the host crystals have been considered. The Mg impurity at cation sites is found to form partially occupied states at the valence-band edge, and may result in p-type conductivity. When Si substitutes for Ga, the impurity band is formed at the conduction-band edge, resulting in n-type conductivity. Si impurities at cation sites, and Mg impurity at anion sites are able to form resonance states in the gap. The influence of impurity clusterization in the host lattice and interstitial sites on electronic properties of c-AlN and c-GaN crystals are modeled. The changes in vacancy- and impurity-state energies, bonding type, localization, density of states at the Fermi level in different host lattices, their dependence on impurity/vacancy concentration are analyzed and compared with the experimental data.

Measurements of Impurity Particle Transport Associated with Drift-Wave Turbulence in MST

NASA Astrophysics Data System (ADS)

Nishizawa, Takashi; Nornberg, Mark; Boguski, John; Craig, Darren; den Hartog, Daniel; Pueschel, M. J.; Sarff, John; Terry, Paul; Williams, Zach; Xing, Zichuan

2017-10-01

Understanding and controlling impurity transport in a toroidal magnetized plasma is one of the critical issues that need to be addressed in order to achieve controlled fusion. Gyrokinetic modeling shows turbulence can drive impurity transport, but direct measurements of the turbulent flux have not been made. Particle balance is typically used to infer the presence of turbulent impurity transport. We report, for the first time in a toroidal plasma, direct measurements of turbulence-driven impurity transport. Trapped electron mode (TEM) turbulence appears in MST plasmas when MHD tearing fluctuations are suppressed. Impurity ion-Doppler spectroscopy is used to correlate impurity density and radial velocity fluctuations associated with TEM. Small Doppler shifts associated with the radial velocity fluctuations (rms 1km/s) are resolved with the use of a new linearized spectrum correlation analysis method, which improves the rejection of Poisson noise. The method employs frequency-domain correlation analysis to expose the fluctuation and transport spectrum. The C+ 2 impurity transport velocity driven by turbulence is found to be 48m/s (inward), which is sufficiently large to impact an impurity flux balance in MST improved-confinement plasmas. This work is supported by the US DOE.

Quantification of active pharmaceutical ingredient and impurities in sildenafil citrate obtained from the Internet.

PubMed

Veronin, Michael A; Nutan, Mohammad T; Dodla, Uday Krishna Reddy

2014-10-01

The accessibility of prescription drugs produced outside of the United States, most notably sildenafil citrate (innovator product, Viagra®), has been made much easier by the Internet. Of greatest concern to clinicians and policymakers is product quality and patient safety. The US Food and Drug Administration (FDA) has issued warnings to potential buyers that the safety of drugs purchased from the Internet cannot be guaranteed, and may present a health risk to consumers from substandard products. The objective of this study was to determine whether generic sildenafil citrate tablets from international markets obtained via the Internet are equivalent to the US innovator product regarding major aspects of pharmaceutical quality: potency, accuracy of labeling, and presence and level of impurities. This will help identify aspects of drug quality that may impact public health risks. A total of 15 sildenafil citrate tablets were obtained for pharmaceutical analysis: 14 generic samples from international Internet pharmacy websites and the US innovator product. According to US Pharmacopeial guidelines, tablet samples were tested using high-performance liquid chromatography for potency of active pharmaceutical ingredient (API) and levels of impurities (impurities A, B, C, and D). Impurity levels were compared with International Conference on Harmonisation (ICH) limits. Among the 15 samples, 4 samples possessed higher impurity B levels than the ICH qualification threshold, 8 samples possessed higher impurity C levels than the ICH qualification threshold, and 4 samples possessed more than 1% impurity quantity of maximum daily dose (MDD). For API, 6 of the samples failed to fall within the 5% assay limit. Quality assurance tests are often used to detect formulation defects of drug products during the manufacturing and/or storage process. Results suggest that manufacturing standards for sildenafil citrate generic drug products compared with the US innovator product are not equivalent with regards to potency and levels of impurities. These findings have implications for safety and effectiveness that should be addressed by clinicians to safeguard consumers who choose to purchase sildenafil citrate and foreign-manufactured drugs, in general, via the Internet.

Quantification of active pharmaceutical ingredient and impurities in sildenafil citrate obtained from the Internet

PubMed Central

Nutan, Mohammad T.; Dodla, Uday Krishna Reddy

2014-01-01

Background: The accessibility of prescription drugs produced outside of the United States, most notably sildenafil citrate (innovator product, Viagra®), has been made much easier by the Internet. Of greatest concern to clinicians and policymakers is product quality and patient safety. The US Food and Drug Administration (FDA) has issued warnings to potential buyers that the safety of drugs purchased from the Internet cannot be guaranteed, and may present a health risk to consumers from substandard products. Objective: The objective of this study was to determine whether generic sildenafil citrate tablets from international markets obtained via the Internet are equivalent to the US innovator product regarding major aspects of pharmaceutical quality: potency, accuracy of labeling, and presence and level of impurities. This will help identify aspects of drug quality that may impact public health risks. Methods: A total of 15 sildenafil citrate tablets were obtained for pharmaceutical analysis: 14 generic samples from international Internet pharmacy websites and the US innovator product. According to US Pharmacopeial guidelines, tablet samples were tested using high-performance liquid chromatography for potency of active pharmaceutical ingredient (API) and levels of impurities (impurities A, B, C, and D). Impurity levels were compared with International Conference on Harmonisation (ICH) limits. Results: Among the 15 samples, 4 samples possessed higher impurity B levels than the ICH qualification threshold, 8 samples possessed higher impurity C levels than the ICH qualification threshold, and 4 samples possessed more than 1% impurity quantity of maximum daily dose (MDD). For API, 6 of the samples failed to fall within the 5% assay limit. Conclusions: Quality assurance tests are often used to detect formulation defects of drug products during the manufacturing and/or storage process. Results suggest that manufacturing standards for sildenafil citrate generic drug products compared with the US innovator product are not equivalent with regards to potency and levels of impurities. These findings have implications for safety and effectiveness that should be addressed by clinicians to safeguard consumers who choose to purchase sildenafil citrate and foreign-manufactured drugs, in general, via the Internet. PMID:25360239

Liquid-purity monitor for the LUX-ZEPLIN dark matter search

NASA Astrophysics Data System (ADS)

Manalaysay, Aaron; Lux-Zeplin Collaboration

2016-03-01

The LUX-ZEPLIN (LZ) experiment will be the first liquid-xenon (LXe) dark matter search to feature a multi-tonne fiducial target. Drawing on the lessons learned in the LUX and ZEPLIN experiments, this next step will probe dark-matter candidates with unprecedented sensitivity. As these LXe detectors have grown larger, so too has the distance over which ionization electrons (from particle interactions) must be drifted through the liquid. Because of this, even minute levels of electronegative impurities can significantly attenuate the ionization signal, and must therefore be closely monitored. I will present the concept of a liquid-purity monitor which uses new and novel techniques, including state-of-the-art UV LEDs and low-work-function materials, and will measure levels of impurities in LZ's liquid circulation line in real time. This device will provide vital supplemental data to the roughly weekly in-situ purity measurements carried out within the detector's active volume, will greatly improve the resolution of the ionization channel in this detector, and will yield instant feedback in response to changing detector conditions.

Device for sampling and enriching impurities in hydrogen comprising hydrogen-permeable membrane

DOEpatents

Ahmed, Shabbir; Papadias, Dionissios D.; Lee, Sheldon D. H.; Kumar, Romesh

2017-01-31

Provided herein are methods and devices to enrich trace quantities of impurities in gaseous mixtures, such as hydrogen fuel. The methods and devices rely on concentration of impurities so as to allow the detection of the impurities using commonly-available detection methods.

Radiated Power and Impurity Concentrations in the EXTRAP-T2R Reversed-Field Pinch

NASA Astrophysics Data System (ADS)

Corre, Y.; Rachlew, E.; Cecconello, M.; Gravestijn, R. M.; Hedqvist, A.; Pégourié, B.; Schunke, B.; Stancalie, V.

2005-01-01

A numerical and experimental study of the impurity concentration and radiation in the EXTRAP-T2R device is reported. The experimental setup consists of an 8-chord bolometer system providing the plasma radiated power and a vacuum-ultraviolet spectrometer providing information on the plasma impurity content. The plasma emissivity profile as measured by the bolometric system is peaked in the plasma centre. A one dimensional Onion Skin Collisional-Radiative model (OSCR) has been developed to compute the density and radiation distributions of the main impurities. The observed centrally peaked emissivity profile can be reproduced by OSCR simulations only if finite particle confinement time and charge-exchange processes between plasma impurities and neutral hydrogen are taken into account. The neutral hydrogen density profile is computed with a recycling code. Simulations show that recycling on metal first wall such as in EXTRAP-T2R (stainless steel vacuum vessel and molybdenum limiters) is compatible with a rather high neutral hydrogen density in the plasma centre. Assuming an impurity concentration of 10% for oxygen and 3% for carbon compared with the electron density, the OSCR calculation including lines and continuum emission reproduces about 60% of the total radiated power with a similarly centrally peaked emissivity profile. The centrally peaked emissivity profile is due to low ionisation stages and strongly radiating species in the plasma core, mainly O4+ (Be-like) and C3+ Li-like.

Chemometrics-assisted chromatographic fingerprinting: An illicit methamphetamine case study.

PubMed

Shekari, Nafiseh; Vosough, Maryam; Tabar Heidar, Kourosh

2017-03-01

The volatile chemical constituents in complex mixtures can be analyzed using gas chromatography with mass spectrometry. This analysis allows the tentative identification of diverse impurities of an illicit methamphetamine sample. The acquired two-dimensional data of liquid-liquid extraction was resolved by multivariate curve resolution alternating curve resolution to elucidate the embedded peaks effectively. This is the first report on the application of a curve resolution approach for chromatogram fingerprinting to identify particularly the embedded impurities of a drug of abuse. Indeed, the strong and broad peak of methamphetamine makes identifying the underlying peaks problematic and even impossible. Mathematical separation instead of conventional chromatographic approaches was performed in a way that trace components embedded in methamphetamine peak were successfully resolved. Comprehensive analysis of the chromatogram, using multivariate curve resolution, resulted in elution profiles and mass spectra for each pure compound. Impurities such as benzaldehyde, benzyl alcohol, benzene, propenyl methyl ketone, benzyl methyl ketone, amphetamine, N-benzyl-2-methylaziridine, phenethylamine, N,N,α-trimethylamine, phenethylamine, N,α,α-trimethylmethamphetamine, N-acetylmethamphetamine, N-formylmethamphetamine, and other chemicals were identified. A route-specific impurity, N-benzyl-2-methylaziridine, indicating a synthesis route based on ephedrine/pseudoephedrine was identified. Moreover, this is the first report on the detection of impurities such as phenethylamine, N,α,α-trimethylamine (a structurally related impurity), and clonitazene (as an adulterant) in an illicit methamphetamine sample. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Donor impurity incorporation during layer growth of Zn II-VI semiconductors

NASA Astrophysics Data System (ADS)

Barlow, D. A.

2017-12-01

The maximum halogen donor concentration in Zn II-VI semiconductors during layer growth is studied using a standard model from statistical mechanics. Here the driving force for incorporation is an increase in entropy upon mixing of the donor impurity into the available anion lattice sites in the host binary. A formation energy opposes this increase and thus equilibrium is attained at some maximum concentration. Considering the halogen donor impurities within the Zn II-VI binary semiconductors ZnO, ZnS, ZnSe and ZnTe, a heat of reaction obtained from reported diatomic bond strengths is shown to be directly proportional to the log of maximum donor concentration. The formation energy can then be estimated and an expression for maximum donor concentration derived. Values for the maximum donor concentration with each of the halogen impurities, within the Zn II-VI compounds, are computed. This model predicts that the halogens will serve as electron donors in these compounds in order of increasing effectiveness as: F, Br, I, Cl. Finally, this result is taken to be equivalent to an alternative model where donor concentration depends upon impurity diffusion and the conduction band energy shift due to a depletion region at the growing crystal's surface. From this, we are able to estimate the diffusion activation energy for each of the impurities mentioned above. Comparisons are made with reported values and relevant conclusions presented.

Improvements to active material for VRLA batteries

NASA Astrophysics Data System (ADS)

Prengaman, R. David

In the past several years, there have been many developments in the materials for lead-acid batteries. Silver in grid alloys for high temperature climates in SLI batteries has increased the silver content of the recycled lead stream. Concern about silver and other contaminants in lead for the active material for VRLA batteries led to the initiation of a study by ALABC at CSIRO. The study evaluated the effects of many different impurities on the hydrogen and oxygen evolution currents in float service for flooded and VRLA batteries at different temperatures and potentials. The study results increased the understanding about the effects of various impurities in lead for use in active material, as well as possible performance and life improvements in VRLA batteries. Some elements thought to be detrimental have been found to be beneficial. Studies have now uncovered the effects of the beneficial elements as well as additives to both the positive and negative active material in increasing battery capacity, extending life and improving recharge. Glass separator materials have also been re-examined in light of the impurities study. Old glass compositions may be revived to give improved battery performance via compositional changes to the glass chemistry. This paper reviews these new developments and outline suggestions for improved battery performance based on unique impurities and additives.

Liquid sodium dip seal maintenance system

DOEpatents

Briggs, Richard L.; Meacham, Sterling A.

1980-01-01

A system for spraying liquid sodium onto impurities associated with liquid dip seals of nuclear reactors. The liquid sodium mixing with the impurities dissolves the impurities in the liquid sodium. The liquid sodium having dissolved and diluted the impurities carries the impurities away from the site thereby cleaning the liquid dip seal and surrounding area. The system also allows wetting of the metallic surfaces of the dip seal thereby reducing migration of radioactive particles across the wetted boundary.

Electronic Structure of p- and n-Type Doping Impurities in Cubic Gallium Nitride

NASA Astrophysics Data System (ADS)

Pentaleri, E. A.; Gubanov, V. A.; Fong, C. Y.; Klein, B. M.

1996-03-01

LMTO-TB calculations were performed to investigate the electronic structure of C, Be, Mg, Si, Zn, and Cd substitutional impurities in cubic GaN (c-GaN). The calculations used 128-site supercells consisting of 64-atoms. Empty spheres of two types occupied the remaining sites. Semi-core Ga 3d states were treated explicitly as valence states. Both amphoteric substitutions were considered for C and Si impurities, while only cation-site substitutions were considered for Be, Mg, Zn, and Cd. All metal impurities formed partially occupied impurity states at the VB edge, which may result in p-type conductivity. C and Si impurities substituted at anion sites form sharp resonances in the gap, and are inactive in creating either p- or n-type carriers. Likewise, cation-site C substitutions introduce to the middle of the band gap strongly localized states that are inactive in carrier formation. Cation-site Si substitutions form an impurity sub-band at the CB edge, leading to n-type conductivity. The DOS at the Fermi level for each impurity-doped c-GaN crystal is used to estimate the most effective p-type doping impurities. The wave-function composition, space, and energy localization is analyzed for different impurities via projections onto the orbital basis and atomic coordinational spheres, and by examining calculated charge-density distributions.

The thermoelectric properties of strongly correlated systems

NASA Astrophysics Data System (ADS)

Cai, Jianwei

Strongly correlated systems are among the most interesting and complicated systems in physics. Large Seebeck coefficients are found in some of these systems, which highlight the possibility for thermoelectric applications. In this thesis, we study the thermoelectric properties of these strongly correlated systems with various methods. We derived analytic formulas for the resistivity and Seebeck coefficient of the periodic Anderson model based on the dynamic mean field theory. These formulas were possible as the self energy of the single impurity Anderson model could be given by an analytic ansatz derived from experiments and numerical calculations instead of complicated numerical calculations. The results show good agreement with the experimental data of rare-earth compound in a restricted temperature range. These formulas help to understand the properties of periodic Anderson model. Based on the study of rare-earth compounds, we proposed a design for the thermoelectric meta-material. This manmade material is made of quantum dots linked by conducting linkers. The quantum dots act as the rare-earth atoms with heavier mass. We set up a model similar to the periodic Anderson model for this new material. The new model was studied with the perturbation theory for energy bands. The dynamic mean field theory with numerical renormalization group as the impurity solver was used to study the transport properties. With these studies, we confirmed the improved thermoelectric properties of the designed material.

Multipolar Kondo effect in a S10-P32 mixture of 173Yb atoms

NASA Astrophysics Data System (ADS)

Kuzmenko, Igor; Kuzmenko, Tetyana; Avishai, Yshai; Jo, Gyu-Boong

2018-02-01

Whereas in the familiar Kondo effect the exchange interaction is dipolar, there are systems in which the exchange interaction is multipolar, as has been realized in a recent experiment. Here, we study multipolar Kondo effect in a Fermi gas of cold 173Yb atoms. Making use of different ac polarizabilities of the electronic ground state Yb (S10 ) and the long-lived metastable state Yb*(P32 ), it is suggested that the latter atoms can be localized and serve as a dilute concentration of magnetic impurities while the former ones remain itinerant. The exchange mechanism between the itinerant Yb and the localized Yb* atoms is analyzed and shown to be antiferromagnetic. The quadrupole and octupole interactions act to enhance the Kondo temperature TK that is found to be experimentally accessible. The bare exchange Hamiltonian needs to be decomposed into dipole (d), quadrupole (q), and octupole (o) interactions in order to retain its form under renormalization group (RG) analysis, in which the corresponding exchange constants (λd,λq, and λo) flow independently. Numerical solution of the RG scaling equations reveals a few finite fixed points. Arguments are presented that the Fermi-liquid fixed point at low temperature is unstable, indicating that the impurity is overscreened, which suggests a non-Fermi-liquid phase. The impurity contributions to the specific heat, entropy, and the magnetic susceptibility are calculated in the weak coupling regime (T ≫TK ), and are compared with the analogous results obtained for the standard case of dipolar exchange interaction (the s -d Hamiltonian).

Extended internal standard method for quantitative 1H NMR assisted by chromatography (EIC) for analyte overlapping impurity on 1H NMR spectra.

PubMed

Saito, Naoki; Kitamaki, Yuko; Otsuka, Satoko; Yamanaka, Noriko; Nishizaki, Yuzo; Sugimoto, Naoki; Imura, Hisanori; Ihara, Toshihide

2018-07-01

We devised a novel extended internal standard method of quantitative 1 H NMR (qNMR) assisted by chromatography (EIC) that accurately quantifies 1 H signal areas of analytes, even when the chemical shifts of the impurity and analyte signals overlap completely. When impurity and analyte signals overlap in the 1 H NMR spectrum but can be separated in a chromatogram, the response ratio of the impurity and an internal standard (IS) can be obtained from the chromatogram. If the response ratio can be converted into the 1 H signal area ratio of the impurity and the IS, the 1 H signal area of the analyte can be evaluated accurately by mathematically correcting the contributions of the 1 H signal area of the impurity overlapping the analyte in the 1 H NMR spectrum. In this study, gas chromatography and liquid chromatography were used. We used 2-chlorophenol and 4-chlorophenol containing phenol as an impurity as examples in which impurity and analyte signals overlap to validate and demonstrate the EIC, respectively. Because the 1 H signals of 2-chlorophenol and phenol can be separated in specific alkaline solutions, 2-chlorophenol is suitable to validate the EIC by comparing analytical value obtained by the EIC with that by only qNMR under the alkaline condition. By the EIC, the purity of 2-chlorophenol was obtained with a relative expanded uncertainty (k = 2) of 0.24%. The purity matched that obtained under the alkaline condition. Furthermore, the EIC was also validated by evaluating the phenol content with the absolute calibration curve method by gas chromatography. Finally, we demonstrated that the EIC was possible to evaluate the purity of 4-chlorophenol, with a relative expanded uncertainty (k = 2) of 0.22%, which was not able to be separated from the 1 H signal of phenol under any condition. Copyright © 2018 Elsevier B.V. All rights reserved.

Development and validation of a selective, sensitive and stability indicating UPLC-MS/MS method for rapid, simultaneous determination of six process related impurities in darunavir drug substance.

PubMed

A, Vijaya Bhaskar Reddy; Yusop, Zulkifli; Jaafar, Jafariah; Aris, Azmi B; Majid, Zaiton A; Umar, Khalid; Talib, Juhaizah

2016-09-05

In this study a sensitive and selective gradient reverse phase UPLC-MS/MS method was developed for the simultaneous determination of six process related impurities viz., Imp-I, Imp-II, Imp-III, Imp-IV, Imp-V and Imp-VI in darunavir. The chromatographic separation was performed on Acquity UPLC BEH C18 (50 mm×2.1mm, 1.7μm) column using gradient elution of acetonitrile-methanol (80:20, v/v) and 5.0mM ammonium acetate containing 0.01% formic acid at a flow rate of 0.4mL/min. Both negative and positive electrospray ionization (ESI) modes were operated simultaneously using multiple reaction monitoring (MRM) for the quantification of all six impurities in darunavir. The developed method was fully validated following ICH guidelines with respect to specificity, linearity, limit of detection (LOD), limit of quantification (LOQ), accuracy, precision, robustness and sample solution stability. The method was able to quantitate Imp-I, Imp-IV, Imp-V at 0.3ppm and Imp-II, Imp-III, and Imp-VI at 0.2ppm with respect to 5.0mg/mL of darunavir. The calibration curves showed good linearity over the concentration range of LOQ to 250% for all six impurities. The correlation coefficient obtained was >0.9989 in all the cases. The accuracy of the method lies between 89.90% and 104.60% for all six impurities. Finally, the method has been successfully applied for three formulation batches of darunavir to determine the above mentioned impurities, however no impurity was found beyond the LOQ. This method is a good quality control tool for the trace level quantification of six process related impurities in darunavir during its synthesis. Copyright © 2016 Elsevier B.V. All rights reserved.

19 CFR 151.46 - Allowance for detectable moisture and impurities.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 19 Customs Duties 2 2010-04-01 2010-04-01 false Allowance for detectable moisture and impurities... Petroleum and Petroleum Products § 151.46 Allowance for detectable moisture and impurities. An allowance for all detectable moisture and impurities present in or upon imported petroleum or petroleum products...

19 CFR 151.46 - Allowance for detectable moisture and impurities.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 19 Customs Duties 2 2013-04-01 2013-04-01 false Allowance for detectable moisture and impurities... Petroleum and Petroleum Products § 151.46 Allowance for detectable moisture and impurities. An allowance for all detectable moisture and impurities present in or upon imported petroleum or petroleum products...

19 CFR 151.46 - Allowance for detectable moisture and impurities.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 19 Customs Duties 2 2014-04-01 2014-04-01 false Allowance for detectable moisture and impurities... Petroleum and Petroleum Products § 151.46 Allowance for detectable moisture and impurities. An allowance for all detectable moisture and impurities present in or upon imported petroleum or petroleum products...

19 CFR 151.46 - Allowance for detectable moisture and impurities.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 19 Customs Duties 2 2012-04-01 2012-04-01 false Allowance for detectable moisture and impurities... Petroleum and Petroleum Products § 151.46 Allowance for detectable moisture and impurities. An allowance for all detectable moisture and impurities present in or upon imported petroleum or petroleum products...

19 CFR 151.46 - Allowance for detectable moisture and impurities.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 19 Customs Duties 2 2011-04-01 2011-04-01 false Allowance for detectable moisture and impurities... Petroleum and Petroleum Products § 151.46 Allowance for detectable moisture and impurities. An allowance for all detectable moisture and impurities present in or upon imported petroleum or petroleum products...

Aluminum anode for aluminum-air battery - Part I: Influence of aluminum purity

NASA Astrophysics Data System (ADS)

Cho, Young-Joo; Park, In-Jun; Lee, Hyeok-Jae; Kim, Jung-Gu

2015-03-01

2N5 commercial grade aluminum (99.5% purity) leads to the lower aluminum-air battery performances than 4N high pure grade aluminum (99.99% purity) due to impurities itself and formed impurity complex layer which contained Fe, Si, Cu and others. The impurity complex layer of 2N5 grade Al declines the battery voltage on standby status. It also depletes discharge current and battery efficiency at 1.0 V which is general operating voltage of aluminum-air battery. However, the impurity complex layer of 2N5 grade Al is dissolved with decreasing discharge voltage to 0.8 V. This phenomenon leads to improvement of discharge current density and battery efficiency by reducing self-corrosion reaction. This study demonstrates the possibility of use of 2N5 grade Al which is cheaper than 4N grade Al as the anode for aluminum-air battery.

Influence of argon impurities on the elastic scattering of x-rays from imploding beryllium capsules

DOE PAGES

Saunders, A. M.; Chapman, D. A.; Kritcher, A. L.; ...

2018-03-01

Here, we investigate the effect of argon impurities on the elastic component of x-ray scattering spectra taken from directly driven beryllium capsule implosions at the OMEGA laser. The plasma conditions were obtained in a previous analysis [18] by fitting the inelastic scattering component. We show that the known argon impurity in the beryllium modifies the elastic scattering due to the larger number of bound electrons. We indeed find significant deviations in the elastic scattering from roughly 1 at.% argon contained in the beryllium. With knowledge of the argon impurity fraction, we use the elastic scattering component to determine the chargemore » state of the compressed beryllium, as the fits are rather insensitive to the argon charge state. Lastly, we discuss how doping small fractions of mid- or high-Z elements into low-Z materials could allow ionization balance studies in dense plasmas.« less

Cd in SnO: Probing structural effects on the electronic structure of doped oxide semiconductors through the electric field gradient at the Cd nucleus

NASA Astrophysics Data System (ADS)

Errico, Leonardo A.; Rentería, Mario; Petrilli, Helena M.

2007-04-01

We perform an ab initio study of the electric field gradient (EFG) at the nucleus of Cd impurities at substitutional Sn sites in crystalline SnO. The full-potential linearized-augmented plane wave and the projector augmented wave methods used here allow us to treat the electronic structure of the doped system and the atomic relaxations introduced by the impurities in the host in a fully self-consistent way using a supercell approach in a state-of-the-art way. Effects of the impurity charge state on the electronic and structural properties are also discussed. Since the EFG is a very subtle quantity, its determination is very useful to probe ground-state properties such as the charge density. We show that the EFG is very sensitive to structural relaxations induced by the impurity. Our theoretical predictions are compared with available experimental results.

Influence of argon impurities on the elastic scattering of x-rays from imploding beryllium capsules

NASA Astrophysics Data System (ADS)

Saunders, A. M.; Chapman, D. A.; Kritcher, A. L.; Schoff, M.; Shuldberg, C.; Landen, O. L.; Glenzer, S. H.; Falcone, R. W.; Gericke, D. O.; Döppner, T.

2018-03-01

We investigate the effect of argon impurities on the elastic component of x-ray scattering spectra taken from directly driven beryllium capsule implosions at the OMEGA laser. The plasma conditions were obtained in a previous analysis [18] by fitting the inelastic scattering component. We show that the known argon impurity in the beryllium modifies the elastic scattering due to the larger number of bound electrons. We indeed find significant deviations in the elastic scattering from roughly 1 at.% argon contained in the beryllium. With knowledge of the argon impurity fraction, we use the elastic scattering component to determine the charge state of the compressed beryllium, as the fits are rather insensitive to the argon charge state. Finally, we discuss how doping small fractions of mid- or high-Z elements into low-Z materials could allow ionization balance studies in dense plasmas.

Imaging the effects of individual zinc impurity atoms on superconductivity in Bi2Sr2CaCu2O8+delta

PubMed

Pan; Hudson; Lang; Eisaki; Uchida; Davis

2000-02-17

Although the crystal structures of the copper oxide high-temperature superconductors are complex and diverse, they all contain some crystal planes consisting of only copper and oxygen atoms in a square lattice: superconductivity is believed to originate from strongly interacting electrons in these CuO2 planes. Substituting a single impurity atom for a copper atom strongly perturbs the surrounding electronic environment and can therefore be used to probe high-temperature superconductivity at the atomic scale. This has provided the motivation for several experimental and theoretical studies. Scanning tunnelling microscopy (STM) is an ideal technique for the study of such effects at the atomic scale, as it has been used very successfully to probe individual impurity atoms in several other systems. Here we use STM to investigate the effects of individual zinc impurity atoms in the high-temperature superconductor Bi2Sr2CaCu2O8+delta. We find intense quasiparticle scattering resonances at the Zn sites, coincident with strong suppression of superconductivity within approximately 15 A of the scattering sites. Imaging of the spatial dependence of the quasiparticle density of states in the vicinity of the impurity atoms reveals the long-sought four-fold symmetric quasiparticle 'cloud' aligned with the nodes of the d-wave superconducting gap which is believed to characterize superconductivity in these materials.

Precipitation of impurities in 9-32-0 grade fluid fertilizers

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

Dillard, E.F.; Scheib, R.M.; Greenwell, B.E.

1986-01-01

For several years TVA has been studying production of 9-32-0 ammonium polyphosphate suspension produced from ammoniated merchant-grade wet-process orthophosphoric acid. Suspensions containing polyphosphate have an advantage over those that contain only orthophosphate in that they can be stored satisfactorily at much lower temperature. However, the introduction of polyphosphate (pyrophosphate anion) complicates the precipitation of impurities and has yielded inconsistent storage characteristics in 9-32-0 fluid fertilizers. Fluorine also has been shown to affect suspension fertilizer properties. The viscosity of 13-38-0 orthophosphate suspension fertilizers is affected by the atomic ratios F:(Al + Fe + Mg). Addition of fluorine prevents sludges and precipitatesmore » in ammonium polyphosphate fertilizer solutions - the proper amount of fluorine is related to the amount of each of the metallic impurities present and also to the fraction of the phosphate present as pyrophosphate. Incorporation of polyphosphate or fluorine or both has been shown to have positive effects on ammoniated wet-process phosphoric acid (WPPA), but they do not report the solubility relationships of the cation impurities (Fe, Al, Mg, and Ca) with respect to the anion constituents (PO/sub 4/, P/sub 2/O/sub 7/, and F). Therefore, a factorial study was developed to determine the solubility relationships of the precipitated metal impurities encountered in 9-32-0 fluid fertilizers. 10 refs., 1 fig., 20 tabs.« less

Quantum Magnetism Applied to the Iron-Pnictides and Rare Earth Pyrochlores

NASA Astrophysics Data System (ADS)

Applegate, Ryan

This dissertation presents computational studies of two families of magnetic materials of significant current interest. The iron pnictides are new high temperature superconductors with interesting parent compound antiferromagnetism. The rare earth pyrochlore material Yb2Ti2O7 is a candidate quantum spin ice. The magnetic and structural phases of individual iron pnictides have both many common features and material specific differences. In an attempt to unify these behaviors as instances of a larger theoretical picture, we use Monte Carlo simulations of a two-dimensional Hamiltonian with coupled Heisenberg-spin and Ising-orbital degrees of freedom. We introduce spin-space and single-ion anisotropies and study the finite temperature transitions in our model. We develop a phase diagram and propose that the interplay of spin and orbital physics in the presence of anisotropy could explain how material details affect the transitions of the pnictide materials. Nuclear magnetic resonance (NMR) can study magnetic materials via the hyperfine interaction and the coupling between the nuclear moment and the field produced by the samples local moment environment. Recent measurements suggest that Zn doped BaFe2As2 may have quantum fluctuations about the striped phase that produce a distribution of fields at As nuclear sites. The non-magnetic ion Zn replaces Fe and can be treated as an impurity which can be studied by a zero-temperature Ising Series expansion method. We propose a Heisenberg-like J1a-J 1b-J2 model which has small ferromagnetic exchanges along the b axis and strong antiferromagnetic exchanges along the a axis. In our impurity model we find that the magnetic moments are everywhere reduced by quantum fluctuations, except on the nearest neighbor site in the AFM direction. We suggest that the presented impurity model may provide an explanation for the experimental measurements. Based on a recently proposed quantum spin ice model, we use numerical linked cluster (NLC) expansions to study thermodynamic properties of Yb 2Ti2O7. We show that high field fitting of inelastic neutron scattering experiments is an excellent method in determining the exchange constants of these materials. We calculate the heat capacity, entropy and magnetization as a function of temperature and field along a few high symmetry field directions. We compare our theoretical predictions to experiments and find remarkable agreement. These studies highlight the importance of localized model Hamiltonians in understanding magnetic properties of complex materials.

Long-term evolution of the impurity composition and impurity events with the ITER-like wall at JET

NASA Astrophysics Data System (ADS)

Coenen, J. W.; Sertoli, M.; Brezinsek, S.; Coffey, I.; Dux, R.; Giroud, C.; Groth, M.; Huber, A.; Ivanova, D.; Krieger, K.; Lawson, K.; Marsen, S.; Meigs, A.; Neu, R.; Puetterich, T.; van Rooij, G. J.; Stamp, M. F.; Contributors, JET-EFDA

2013-07-01

This paper covers aspects of long-term evolution of intrinsic impurities in the JET tokamak with respect to the newly installed ITER-like wall (ILW). At first the changes related to the change over from the JET-C to the JET-ILW with beryllium (Be) as the main wall material and tungsten (W) in the divertor are discussed. The evolution of impurity fluxes in the newly installed W divertor with respect to studying material migration is described. In addition, a statistical analysis of transient impurity events causing significant plasma contamination and radiation losses is shown. The main findings comprise a drop in carbon content (×20) (see also Brezinsek et al (2013 J. Nucl. Mater. 438 S303)), low oxygen content (×10) due to the Be first wall (Douai et al 2013 J. Nucl. Mater. 438 S1172-6) as well as the evolution of the material mix in the divertor. Initially, a short period of repetitive ohmic plasmas was carried out to study material migration (Krieger et al 2013 J. Nucl. Mater. 438 S262). After the initial 1600 plasma seconds the material surface composition is, however, still evolving. With operational time, the levels of recycled C are increasing slightly by 20% while the Be levels in the deposition-dominated inner divertor are dropping, hinting at changes in the surface layer material mix made of Be, C and W. A steady number of transient impurity events, consisting of W and constituents of inconel, is observed despite the increase in variation in machine operation and changes in magnetic configuration as well as the auxiliary power increase.

A New Scaling for Divertor Detachment

NASA Astrophysics Data System (ADS)

Goldston, Robert

2017-10-01

The ITER design and future fusion power plant designs depend on divertor detachment, whether partial, pronounced or complete, both to limit heat flux to plasma-facing components and to limit surface erosion due to sputtering. Generally the parallel heat flux, estimated as proportional to Psep / R or Psep B / R , is used as a proxy for the difficulty of achieving detachment. Here we argue that the impurity cooling required for detachment is strongly dependent on the upstream separatrix density, which is limited by Greenwald scaling. Taking this into account self-consistently, along with the Heuristic Drift (HD) model for the SOL width, and using a Lengyel radiation model that includes non-coronal effects, we find that the relative impurity concentration, cz ≡nz /ne , required for detachment scales dominantly as cz Psep /Bp(nsep /nGW) 2 . The absence of any explicit favorable size scaling is concerning, as Psep must increase by an order of magnitude from present experiments to an economic fusion power system, while increases in the poloidal magnetic field strength are limited by magnet technology and MHD stability. This result should not be surprising, as it follows from the simplest scaling, Psep czne2VSOL , taking into account the Greenwald density limit and the HD SOL volume scaling. Reinke has combined a similar approach with the requirement to maintain H-mode, which sets a lower limit on Psep, and also arrives at an incentive for high field and disincentive for large size. These results should be challenged by comparison with 2D divertor codes and with measurements on existing experiments. In particular measurements are required for extrinsic divertor impurity concentration over a range of power and density conditions far from the regime where detachment can be achieved with deuterium puffing and intrinsic impurities alone. Nonetheless, these results suggest that higher magnetic field, stronger shaping, double-null operation, `advanced' divertor magnetic and baffle configurations, as well as lithium vapor targets merit greater attention. This work supported by the US DOE under contract DE-AC02-09CH11466.

Separation of harmful impurities from refuse derived fuels (RDF) by a fluidized bed.

PubMed

Krüger, B; Mrotzek, A; Wirtz, S

2014-02-01

In firing systems of cement production plants and coal-fired power plants, regular fossil fuels are increasingly substituted by alternative fuels. Rising energy prices and ambitious CO2-reduction goals promote the use of alternative fuels as a significant contribution to efficient energy recovery. One possibility to protect energy resources are refuse-derived fuels (RDF), which are produced during the treatment of municipal solid, commercial and industrial waste. The waste fractions suitable for RDF have a high calorific value and are often not suitable for material recycling. With current treatment processes, RDF still contains components which impede the utilization in firing systems or limit the degree of substitution. The content of these undesired components may amount to 4 wt%. These, in most cases incombustible particles which consist of mineral, ceramic and metallic materials can cause damages in the conveying systems (e. g. rotary feeder) or result in contaminations of the products (e. g. cement, chalk). Up-to-date separation processes (sieve machine, magnet separator or air classifier) have individual weaknesses that could hamper a secure separation of these particles. This article describes a new technology for the separation of impurities from refuse derived fuels based on a rotating fluidized bed. In this concept a rotating motion of the particle bed is obtained by the tangential injection of the fluidization gas in a static geometry. The RDF-particles experience a centrifugal force which fluidized the bed radially. The technical principle allows tearing up of particle clusters to single particles. Radially inwards the vertical velocity is much lower thus particles of every description can fall down there. For the subsequent separation of the particles by form and density an additionally cone shaped plate was installed in the centre. Impurities have a higher density and a compact form compared to combustible particles and can be separated with a high efficiency. The new technology was experimentally investigated and proven using model-RDF, actual-RDF and impurities of different densities. In addition, numerical simulations were also done. The fluidization chamber was operated in batch mode. The article describes experiences and difficulties in using rotating fluidized bed systems. Copyright © 2013 Elsevier Ltd. All rights reserved.

Analysis of the Effects of Impurities in Silicon. [to determine solar cell efficiency

NASA Technical Reports Server (NTRS)

Wohlgemuth, J. H.; Lafky, W. M.; Burkholder, J. H.

1979-01-01

A solar cell fabrication and analysis program to determine the effects on the resultant solar cell efficiency of impurities incorporated into silicon is conducted. Flight quality technologies and quality assurance are employed to assure that variations in cell performance are due to the impurities incorporated in the silicon. The type and level of impurity doping in each test lot is given and the mechanism responsible for the degradation of cell performance is identified and correlated to the doped impurities.

Core Radial Electric Field and Transport in Wendelstein 7-X Plasmas

NASA Astrophysics Data System (ADS)

Pablant, Novimir

2016-10-01

Results from the investigation of core transport and the role of the radial electric field profile (Er) in the first operational phase of the Wendelstein 7-X (W7-X) stellarator are presented. In stellarator plasmas, the details of the Er profile are expected to have a strong effect on both the particle and heat fluxes. Neoclassical particle fluxes are not intrinsically ambipolar, which leads to the formation of a radial electric field that enforces ambipolarity. The radial electric field is closely related to the perpendicular plasma flow (u⊥) through the force balance equation. This allows the radial electric field to be inferred from measurements of the perpendicular flow velocity from the x-ray imaging crystal spectrometer (XICS) and correlation reflectometry diagnostics. Large changes in the perpendicular rotation, on the order of Δu⊥ 5km /s (ΔEr 12kV / m), have been observed within a set of experiments where the heating power was stepped down from 2 MW to 0.6 MW . These experiments are examined in detail to explore the relationship between, heating power, response of the temperature and density profiles and the response of the radial electric field. Estimations of the core transport are based on power balance and utilize electron temperature (Te) profiles from the ECE and Thomson scattering, electron density profiles (ne) from interferometry and Thomson scattering, ion temperature (Ti) profiles from XICS, along with measurements of the total stored energy and radiated power. Also described are a set core impurity confinement experiments and results. Impurity confinement has been investigated through the injection of trace amount of argon impurity gas at the plasma edge in conjunction with measurements of the density of various ionization states of argon from the XICS and High Efficiency eXtreme-UV Overview Spectrometer (HEXOS) diagnostics. Finally the inferred Er and heat flux profiles are compared to initial neoclassical calculations using measured plasma profiles. On behalf of the W7-X Team.

First-Principles Study of Carbon and Vacancy Structures in Niobium

DOE PAGES

Ford, Denise C.; Zapol, Peter; Cooley, Lance D.

2015-04-03

The interstitial chemical impurities hydrogen, oxygen, nitrogen, and carbon are important for niobium metal production, and particularly for the optimization of niobium SRF technology. These atoms are present in refined sheets and can be absorbed into niobium during processing treatments, resulting in changes to the residual resistance and the performance of SRF cavities. A first-principles approach is taken to study the properties of carbon in niobium, and the results are compared and contrasted with the properties of the other interstitial impurities. The results indicate that C will likely form precipitates or atmospheres around defects rather than strongly bound complexes withmore » other impurities. Based on the analysis of carbon and hydrogen near niobium lattice vacancies and small vacancy chains and clusters, the formation of extended carbon chains and hydrocarbons is not likely to occur. Association of carbon with hydrogen atoms can, however, occur through the strain fields created by interstitial binding of the impurity atoms. In conclusion, calculated electronic densities of states indicate that interstitial C may have a similar effect as interstitial O on the superconducting transition temperature of Nb.« less

Estimation of sheath potentials in front of ASDEX upgrade ICRF antenna with SSWICH asymptotic code

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

Křivská, A., E-mail: alena.krivska@rma.ac.be; Bobkov, V.; Jacquot, J.

Multi-megawatt Ion Cyclotron Range of Frequencies (ICRF) heating became problematic in ASDEX Upgrade (AUG) tokamak after coating of ICRF antenna limiters and other plasma facing components by tungsten. Strong impurity influx was indeed produced at levels of injected power markedly lower than in the previous experiments. It is assumed that the impurity production is mainly driven by parallel component of Radio-Frequency (RF) antenna electric near-field E// that is rectified in sheaths. In this contribution we estimate poloidal distribution of sheath Direct Current (DC) potential in front of the ICRF antenna and simulate its relative variations over the parametric scans performedmore » during experiments, trying to reproduce some of the experimental observations. In addition, relative comparison between two types of AUG ICRF antenna configurations, used for experiments in 2014, has been performed. For this purpose we use the Torino Polytechnic Ion Cyclotron Antenna (TOPICA) code and asymptotic version of the Self-consistent Sheaths and Waves for Ion Cyclotron Heating (SSWICH) code. Further, we investigate correlation between amplitudes of the calculated oscillating sheath voltages and the E// fields computed at the lateral side of the antenna box, in relation with a heuristic antenna design strategy at IPP Garching to mitigate RF sheaths.« less

High-Z plasma facing components in fusion devices: boundary conditions and operational experiences

NASA Astrophysics Data System (ADS)

Neu, R.

2006-04-01

In present day fusion devices optimization of the performance and experimental freedom motivates the use of low-Z plasma facing materials (PFMs). However, in a future fusion reactor, for economic reasons, a sufficient lifetime of the first wall components is essential. Additionally, tritium retention has to be small to meet safety requirements. Tungsten appears to be the most realistic material choice for reactor plasma facing components (PFCs) because it exhibits the lowest erosion. But besides this there are a lot of criteria which have to be fulfilled simultaneously in a reactor. Results from present day devices and from laboratory experiments confirm the advantages of high-Z PFMs but also point to operational restrictions, when using them as PFCs. These are associated with the central impurity concentration, which is determined by the sputtering yield, the penetration of the impurities and their transport within the confined plasma. The restrictions could exclude successful operation of a reactor, but concomitantly there exist remedies to ameliorate their impact. Obviously some price has to be paid in terms of reduced performance but lacking of materials or concepts which could substitute high-Z PFCs, emphasis has to be put on the development and optimization of reactor-relevant scenarios which incorporate the experiences and measures.

GITR Simulation of Helium Exposed Tungsten Erosion and Redistribution in PISCES-A

NASA Astrophysics Data System (ADS)

Younkin, T. R.; Green, D. L.; Doerner, R. P.; Nishijima, D.; Drobny, J.; Canik, J. M.; Wirth, B. D.

2017-10-01

The extreme heat, charged particle, and neutron flux / fluence to plasma facing materials in magnetically confined fusion devices has motivated research to understand, predict, and mitigate the associated detrimental effects. Of relevance to the ITER divertor is the helium interaction with the tungsten divertor, the resulting erosion and migration of impurities. The linear plasma device PISCES A has performed dedicated experiments for high (4x10-22 m-2s-1) and low (4x10-21 m-2s-1) flux, 250 eV He exposed tungsten targets to assess the net and gross erosion of tungsten and volumetric transport. The temperature of the target was held between 400 and 600 degrees C. We present results of the erosion / migration / re-deposition of W during the experiment from the GITR (Global Impurity Transport) code coupled to materials response models. In particular, the modeled and experimental W I emission spectroscopy data for the 429.4 nm wavelength and net erosion through target and collector mass difference measurements are compared. Overall, the predictions are in good agreement with experiments. This material is supported by the US DOE, Office of Science, Office of Fusion Energy Sciences and Office of Advanced Scientific Computing Research through the SciDAC program on Plasma-Surface Interactions.

Phase transition in one Josephson junction with a side-coupled magnetic impurity

NASA Astrophysics Data System (ADS)

Zhi, Li-Ming; Wang, Xiao-Qi; Jiang, Cui; Yi, Guang-Yu; Gong, Wei-Jiang

2018-04-01

This work focuses on one Josephson junction with a side-coupled magnetic impurity. And then, the Josephson phase transition is theoretically investigated, with the help of the exact diagonalization approach. It is found that even in the absence of intradot Coulomb interaction, the magnetic impurity can efficiently induce the phenomenon of Josephson phase transition, which is tightly related to the spin correlation manners (i.e., ferromagnetic or antiferromagnetic) between the impurity and the junction. Moreover, the impurity plays different roles when it couples to the dot and superconductor, respectively. This work can be helpful in describing the influence of one magnetic impurity on the supercurrent through the Josephson junction.

The effect of secondary impurities on solar cell performance

NASA Technical Reports Server (NTRS)

Hill, D. E.; Gutsche, H. W.; Wang, M. S.; Gupta, K. P.; Tucker, W. F.; Dowdy, J. D.; Crepin, R. J.

1976-01-01

Czochralski and float zone sigle crystals of silicon were doped with the primary impurities B or P so that a resistivity of 0.5 ohm cm resulted, and in addition doped with certain secondary impurities including Al, C, Cr, Cu, Fe, Mg, Mn, Na, Ni, O, Ti, V, and Zr. The actual presence of these impurities was confirmed by analysis of the crystals. Solar cell performance was evaluated and found to be degraded most significantly by Ti, V, and Zr and to some extent by most of the secondary impurities considered. These results are of significance to the low cost silicon program, since any such process would have to yield at least tolerable levels of these impurities.

Numerical renormalization group method for entanglement negativity at finite temperature

NASA Astrophysics Data System (ADS)

Shim, Jeongmin; Sim, H.-S.; Lee, Seung-Sup B.

2018-04-01

We develop a numerical method to compute the negativity, an entanglement measure for mixed states, between the impurity and the bath in quantum impurity systems at finite temperature. We construct a thermal density matrix by using the numerical renormalization group (NRG), and evaluate the negativity by implementing the NRG approximation that reduces computational cost exponentially. We apply the method to the single-impurity Kondo model and the single-impurity Anderson model. In the Kondo model, the negativity exhibits a power-law scaling at temperature much lower than the Kondo temperature and a sudden death at high temperature. In the Anderson model, the charge fluctuation of the impurity contributes to the negativity even at zero temperature when the on-site Coulomb repulsion of the impurity is finite, while at low temperature the negativity between the impurity spin and the bath exhibits the same power-law scaling behavior as in the Kondo model.

Silicon materials task of the Low Cost Solar Array Project: Effect of impurities and processing on silicon solar cells

NASA Technical Reports Server (NTRS)

Hopkins, R. H.; Davis, J. R.; Rohatgi, A.; Hanes, M. H.; Rai-Choudhury, P.; Mollenkopf, H. C.

1982-01-01

The effects of impurities and processing on the characteristics of silicon and terrestrial silicon solar cells were defined in order to develop cost benefit relationships for the use of cheaper, less pure solar grades of silicon. The amount of concentrations of commonly encountered impurities that can be tolerated in typical p or n base solar cells was established, then a preliminary analytical model from which the cell performance could be projected depending on the kinds and amounts of contaminants in the silicon base material was developed. The impurity data base was expanded to include construction materials, and the impurity performace model was refined to account for additional effects such as base resistivity, grain boundary interactions, thermal processing, synergic behavior, and nonuniform impurity distributions. A preliminary assessment of long term (aging) behavior of impurities was also undertaken.

Macromolecule Crystal Quality Improvement in Microgravity: The Role of Impurities

NASA Technical Reports Server (NTRS)

Judge, Russell A.; Snell, Edward H.; Pusey, Marc L.; Sportiello, Michael G.; Todd, Paul; Bellamy, Henry; Borgstahl, Gloria E.; Pokros, Matt; Cassanto, John M.

2000-01-01

While macromolecule impurities may affect crystal size and morphology the over-riding question is; "How do macromolecule impurities effect crystal X-ray quality and diffraction resolution?" In the case of chicken egg white lysozyme, crystals can be grown in the presence of a number of impurities without affecting diffraction resolution. One impurity however, the lysozyme dimer, does negatively impact the X-ray crystal properties. Crystal quality improvement as a result of better partitioning of this impurity during crystallization in microgravity has been reported'. In our recent experimental work dimer partitioning was found to be not significantly different between the two environments. Mosaicity analysis of pure crystals showed a reduced mosaicity and increased signal to noise for the microgravity grown crystals. Dimer incorporation however, did greatly reduce the resolution limit in both ground and microgravity grown crystals. These results indicate that impurity effects in microgravity are complex and may rely on the conditions or techniques employed.

Separation and characterization of allergic polymerized impurities in cephalosporins by 2D-HPSEC×LC-IT-TOF MS.

PubMed

Xu, Yu; Wang, DanDan; Tang, Lan; Wang, Jian

2017-10-25

Eleven unknown allergic impurities in cefodizime, cefmenoxime and cefonicid were separated and characterized by a trap-free two-dimensional high performance size exclusion chromatography (HPSEC) and reversed phase liquid chromatography (RP-HPLC) coupled to high resolution ion trap/time-of-flight mass spectrometry (2D-HPSEC×LC-IT-TOF MS) with positive and negative modes of electrospray ionization method. Separation and characterization the allergic polymerized impurities in β-lactam antibiotics were on the basis of column-switching technique which effectively combined the advantages of HPSEC and the ability of RP-HPLC to identify the special impurities. In the first dimension HPSEC, the column was Xtimate SEC-120 analytical column (7.8mm×30cm, 5μm), and the gradient elution used pH 7.0 buffer-acetonitrile as mobile phase And the second dimension analytical column was ZORBAX SB-C18 (4.6×150mm, 3.5μm) with ammonium formate solution (10mM) and ammonium formate (8mM) in [acetonitrile-water (4:1, v/v)] solution as mobile phase. Structures of eleven unknown impurities were deduced based on the high resolution MS n data with both positive and negative modes, in which nine impurities were polymerized impurities. The forming mechanism of β-lactam antibiotic polymerization in cephalosporins was also studied. The question on incompatibility between non-volatile salt mobile phase and mass spectrometry was solved completely by multidimensional heart-cutting approaches and online demineralization technique, which was worthy of widespread use and application for the advantages of stability and repeatability. Copyright © 2017. Published by Elsevier B.V.

Local magnetizations in impure two-dimensional antiferromagnets

NASA Astrophysics Data System (ADS)

van Luijk, J. A.; Arts, A. F. M.; de Wijn, H. W.

1980-03-01

The local magnetizations near dilute substitutional impurities in the quadratic-layer antiferromagnet K2MnF4 are studied both experimentally and theoretically. The impurities considered are the nonmagnetic Zn and Mg, as well as Ni. The magnetizations are probed through the positions of the impurity-associated satellites in the nuclear magnetic resonance of the out-of-layer and in-layer 19F nuclei adjacent to the magnetic ions. It is discussed in which way the effects of lattice deformations can be eliminated in order to obtain the variations of the local magnetizations with temperature. The theoretical treatment is based on Green's-function techniques. The decoupling employed is within the local spin-deviation operators and accounts for correlation between nearest neighbors. It reduces the renormalized spin-wave Hamiltonian to an effective quadratic form, rendering decoupling of Green's functions unnecessary. The spectral distributions of the excitations are calculated including local modes. The theory is subsequently applied to the 13-site cluster consisting of the impurity and the first three shells of Mn around it. Good agreement is found. The magnetization is significantly modified in the first shell. The further shells are only weakly affected, however somewhat stronger than in comparable three-dimensional systems. For nonmagnetic impurities the thermal spin deviation in the first shell is about 13 larger than that of the host; in the Ni-doped system the additional deviations are within 1%. The zero-point deviation of the Ni is 0.11 units of spin, as compared to 0.17 in the host. A further experimental result is a uniform shift, increasing with concentration, of the sublattice magnetization at large distance from the impurity. It must be related to the finite density of states near the zone center in two-dimensional systems. Finally, some data are presented on the local susceptibilities.

19 CFR 158.13 - Allowance for moisture and impurities.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 19 Customs Duties 2 2011-04-01 2011-04-01 false Allowance for moisture and impurities. 158.13... EXPORTED Damaged or Defective Merchandise § 158.13 Allowance for moisture and impurities. (a) Application... section 507, Tariff Act of 1930, as amended (19 U.S.C. 1507), for all detectable moisture and impurities...

19 CFR 158.13 - Allowance for moisture and impurities.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 19 Customs Duties 2 2014-04-01 2014-04-01 false Allowance for moisture and impurities. 158.13... EXPORTED Damaged or Defective Merchandise § 158.13 Allowance for moisture and impurities. (a) Application... section 507, Tariff Act of 1930, as amended (19 U.S.C. 1507), for all detectable moisture and impurities...

19 CFR 158.13 - Allowance for moisture and impurities.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 19 Customs Duties 2 2012-04-01 2012-04-01 false Allowance for moisture and impurities. 158.13... EXPORTED Damaged or Defective Merchandise § 158.13 Allowance for moisture and impurities. (a) Application... section 507, Tariff Act of 1930, as amended (19 U.S.C. 1507), for all detectable moisture and impurities...

19 CFR 158.13 - Allowance for moisture and impurities.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 19 Customs Duties 2 2010-04-01 2010-04-01 false Allowance for moisture and impurities. 158.13... EXPORTED Damaged or Defective Merchandise § 158.13 Allowance for moisture and impurities. (a) Application... section 507, Tariff Act of 1930, as amended (19 U.S.C. 1507), for all detectable moisture and impurities...

19 CFR 158.13 - Allowance for moisture and impurities.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 19 Customs Duties 2 2013-04-01 2013-04-01 false Allowance for moisture and impurities. 158.13... EXPORTED Damaged or Defective Merchandise § 158.13 Allowance for moisture and impurities. (a) Application... section 507, Tariff Act of 1930, as amended (19 U.S.C. 1507), for all detectable moisture and impurities...

Process of electrolysis and fractional crystallization for aluminum purification

DOEpatents

Dawless, R.K.; Bowman, K.A.; Mazgaj, R.M.; Cochran, C.N.

1983-10-25

A method is described for purifying aluminum that contains impurities, the method including the step of introducing such aluminum containing impurities to a charging and melting chamber located in an electrolytic cell of the type having a porous diaphragm permeable by the electrolyte of the cell and impermeable to molten aluminum. The method includes further the steps of supplying impure aluminum from the chamber to the anode area of the cell and electrolytically transferring aluminum from the anode area to the cathode through the diaphragm while leaving impurities in the anode area, thereby purifying the aluminum introduced into the chamber. The method includes the further steps of collecting the purified aluminum at the cathode, and lowering the level of impurities concentrated in the anode area by subjecting molten aluminum and impurities in said chamber to a fractional crystallization treatment wherein eutectic-type impurities crystallize and precipitate out of the aluminum. The eutectic impurities that have crystallized are physically removed from the chamber. The aluminum in the chamber is now suited for further purification as provided in the above step of electrolytically transferring aluminum through the diaphragm. 2 figs.