The screening of charged impurities in bilayer graphene

International Nuclear Information System (INIS)

Zhang Wenjing; Li, Lain-Jong

2010-01-01

Positively charged impurities were introduced into a bilayer graphene (BLG) transistor by n-doping with dimethylformamide. Subsequent exposure of the BLG device to moisture resulted in a positive shift of the Dirac point and an increase of hole mobility, suggesting that moisture could reduce the scattering strength of the existing charged impurities. In other words, moisture screened off the 'effective density' of charged impurities. At the early stage of moisture screening the scattering of hole carriers is dominated by long-range Coulomb scatter, but an alternative scattering mechanism should also be taken into consideration when the effective density of impurities is further lowered on moisture exposure.

Impurity diffusion activation energies in Al from first principles

NARCIS (Netherlands)

Simonovic, D.; Sluiter, M.H.

2009-01-01

Activation energies for vacancy-mediated impurity diffusion in face-centered-cubic aluminum have been computed ab initio for all technologically important alloying elements, as well as for most of the lanthanides. The so-called five-frequency rate model is used to establish the limiting vacancy

The effects of impurity composition and concentration in reactor structure material on neutron activation inventory in pressurized water reactor

Energy Technology Data Exchange (ETDEWEB)

Cha, Gil Yong; Kim, Soon Young [RADCORE, Daejeon (Korea, Republic of); Lee, Jae Min [TUV Rheinland Korea, Seoul (Korea, Republic of); Kim, Yong Soo [Hanyang University, Seoul (Korea, Republic of)

2016-06-15

The neutron activation inventories in reactor vessel and its internals, and bio-shield of a PWR nuclear power plant were calculated to evaluate the effect of impurity elements contained in the structural materials on the activation inventory. Carbon steel is, in this work, used as the reactor vessel material, stainless steel as the reactor vessel internals, and ordinary concrete as the bio-shield. For stainless steel and carbon steel, one kind of impurity concentration was employed, and for ordinary concrete five kinds were employed in this study using MCNP5 and FISPACT for the calculation of neutron flux and activation inventory, respectively. As the results, specific activities for the cases with impurity elements were calculated to be more than twice than those for the cases without impurity elements in stainless and carbon steel. Especially, the specific activity for the concrete material with impurity elements was calculated to be 30 times higher than that without impurity. Neutron induced reactions and activation inventories in each material were also investigated, and it is noted that major radioactive nuclide in steel material is Co-60 from cobalt impurity element, and, in concrete material, Co-60 and Eu-152 from cobalt and europium impurity elements, respectively. The results of this study can be used for nuclear decommissioning plan during activation inventory assessment and regulation, and it is expected to be used as a reference in the design phase of nuclear power plant, considering the decommissioning of nuclear power plants or nuclear facilities.

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

Science.gov (United States)

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.

Defect-impurity interactions in ion-implanted metals

International Nuclear Information System (INIS)

Turos, A.

1986-01-01

An overview of defect-impurity interactions in metals is presented. When point defects become mobile they migrate towards the sinks and on the way can be captured by impurity atoms forming stable associations so-called complexes. In some metallic systems complexes can also be formed athermally during ion implantation by trapping point defects already in the collision cascade. An association of a point defect with an impurity atom leads to its displacement from the lattice site. The structure and stability of complexes are strongly temperature dependent. With increasing temperature they dissociate or grow by multiple defect trapping. The appearance of freely migrating point defects at elevated temperatures, due to ion bombardment or thermal annealing, causes via coupling with defect fluxes, important impurity redistribution. Because of the sensitivity of many metal-in-metal implanted systems to radiation damage the understanding of this processes is essential for a proper interpretation of the lattice occupancy measurements and the optimization of implantation conditions. (author)

Instrumental neutron-activation determination of impurities in lead and titanium compounds

Energy Technology Data Exchange (ETDEWEB)

Popova, I L

1980-01-01

Instrumental neutron-activation analysis was used to determine 22 impurities in lead and titanium compounds (e.g. PbO, Pb/NO3/2, and TiO2) used as raw materials for ferroelectrics. Five elements (Al, V, Mn, Sc, and Se) were determined by short-lived isotopes and 17 elements were determined by long-lived isotopes. The detection limits were 7 x 10 to the -3rd to 2 x 10 to the -8th %. A substantial difference in concentrations of certain impurity elements has been found in different series of lead and titanium oxides of similar purity.

An Evaluation Method for Activation Analysis using Pre-evaluated Contribution of Nuclides with Impurity

Energy Technology Data Exchange (ETDEWEB)

Woo, Myeong Hyeon; Kim, Song Hyun; Kim, Do Hyun; Shin, Chang Ho [Hanyang University, Seoul (Korea, Republic of); Kim, Gee Suck [KAERI, Daejeon (Korea, Republic of)

2016-05-15

Nuclides in radiation facilities become unstable from nuclear reaction. It emits residual radiation to be stable. Some unstable nuclides remain after operation in the material. It continuously emits the radiation, which has a harmful effect to worker when they try maintenance and plant decommissioning. It is known that residual radiation from impurity occupies a large portion of the radiation dose. If impurity concentration is higher than expectation, the effects of residual radiation could be underestimated. Therefore, estimation of residual radiation is repeatedly calculated according to impurity concentration. In this study, an approach estimating the activation was proposed using pre-evaluated nuclide's contribution to reduce the calculation time and effort of worker. In this study, in order to reduce the calculation time and effort of worker, activation analysis method based on pre-evaluated nuclide contribution was proposed. This method was verified using concreate activation problem, which is located in nuclear power plant. The results show that our proposed method has good agreement with Bateman equation.

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

Science.gov (United States)

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.

Surface segregation of the metal impurity to the (1 0 0) surface of fcc ...

Indian Academy of Sciences (India)

good relation to the differences in surface energy between the impurity and host crystals ΔQ ..... mobile impurity are treated as movable discrete particles. ..... [64] J Siera, van Delft FCMJM, A D van Langeveld and B E Nieuwenhuys, Surf. Sci.

Impurity diffusion in transition-metal oxides

International Nuclear Information System (INIS)

Peterson, N.L.

1982-06-01

Intrinsic tracer impurity diffusion measurements in ceramic oxides have been primarily confined to CoO, NiO, and Fe 3 O 4 . Tracer impurity diffusion in these materials and TiO 2 , together with measurements of the effect of impurities on tracer diffusion (Co in NiO and Cr in CoO), are reviewed and discussed in terms of impurity-defect interactions and mechanisms of diffusion. Divalent impurities in divalent solvents seem to have a weak interaction with vacancies whereas trivalent impurities in divalent solvents strongly influence the vacancy concentrations and significantly reduce solvent jump frequencies near a trivalent impurity. Impurities with small ionic radii diffuse more slowly with a larger activation energy than impurities with larger ionic radii for all systems considered in this review. Cobalt ions (a moderate size impurity) diffuse rapidly along the open channels parallel to the c-axis in TiO 2 whereas chromium ions (a smaller-sized impurity) do not. 60 references, 11 figures

Plasmon-enhanced phonon and ionized impurity scattering in doped silicon

International Nuclear Information System (INIS)

Chen, Ming-Jer; Hsieh, Shang-Hsun; Chen, Chuan-Li

2015-01-01

Historically, two microscopic electron scattering calculation methods have been used to fit macroscopic electron mobility data in n-type silicon. The first method was performed using a static system that included long-range electron-plasmon scattering; however, the well-known Born approximation fails in this case when dealing with electron-impurity scattering. In the second method, sophisticated numerical simulations were developed around plasmon-excited potential fluctuations and successfully reproduced the mobility data at room temperature. In this paper, we propose a third method as an alternative to the first method. First, using a fluctuating system, which was characterized on the basis of our recently experimentally extracted plasmon-excited potential fluctuations, the microscopic calculations reveal enhanced short-range scattering of electrons by phonons and ionized impurities due to increased electron temperature and increased screening length, respectively. The increased hot electron population makes the Born approximation hold, which eases the overall calculation task substantially. Then, we return to the static system while incorporating plasmon-enhanced impurity scattering. The resulting macroscopic electron mobility shows fairly good agreement with data over wide ranges of temperatures (200–400 K) and doping concentrations (10 15 –10 20  cm −3 ). Application of the proposed method to strained silicon is also demonstrated

Characterization of light element impurities in ultrathin silicon-on-insulator layers by luminescence activation using electron irradiation

International Nuclear Information System (INIS)

Nakagawa-Toyota, Satoko; Tajima, Michio; Hirose, Kazuyuki; Ohshima, Takeshi; Itoh, Hisayoshi

2009-01-01

We analyzed light element impurities in ultrathin top Si layers of silicon-on-insulator (SOI) wafers by luminescence activation using electron irradiation. Photoluminescence (PL) analysis under ultraviolet (UV) light excitation was performed on various commercial SOI wafers after the irradiation. We detected the C-line related to a complex of interstitial carbon and oxygen impurities and the G-line related to a complex of interstitial and substitutional carbon impurities in the top Si layer with a thickness down to 62 nm after electron irradiation. We showed that there were differences in the impurity concentration depending on the wafer fabrication methods and also that there were variations in these concentrations in the respective wafers. Xenon ion implantation was used to activate top Si layers selectively so that we could confirm that the PL signal under the UV light excitation comes not from substrates but from top Si layers. The present method is a very promising tool to evaluate the light element impurities in top Si layers. (author)

Study by nuclear techniques of the impurity-defect interaction in implanted metals

International Nuclear Information System (INIS)

Thome, Lionel.

1978-01-01

The properties of out equilibrium alloys formed by impurity implantation are strongly influenced by radiation damage created during implantation. This work presents a study, via hyperfine interaction and lattice location experiments, of the impurity-defect interaction in ion implanted metals. When the impurity and defect concentrations in the implanted layer are small, i.e. when impurities are uniformly recoil implanted in the whole crystal volume following a nuclear reaction (Aq In experiments), the impurity interacts with its own damage cascade. In this case, a vacancy is found to be trapped by a fraction of impurities during an athermal process. The value of this fraction does not seem to depend critically on impurity and host. When the impurity and defect concentrations are such that defect cascades interact, i.e. when impurities are implanted with an isotope separator (Fe Yb experiments), the observed impurity-vacancy (or vacancy cluster) interactions depend then strongly on the nature of impurity and host. An empirical relation, which indicates the importance of elastic effects, has been found between the proportion of impurities interacting with defects and the difference between impurity and host atom radii. At implantation temperature such that vacancies are mobile, the impurity-defect interaction depends essentially on vacancy migration. A model based on chemical kinetics has been developed to account for the variation with temperature of measured quantities [fr

Determination of impurities in beryl by neutron activation analysis

International Nuclear Information System (INIS)

Swain, K.K.; Dalvi, Aditi A.; Ajith, Nicy

2015-01-01

Beryl is a chemically complex and highly compositionally variable gem-forming mineral found in a variety of locations worldwide. Pure beryl is colorless, but the presence of impurities imparts colors such as green, blue, yellow, red, and white. It is one of the most important gem minerals and the gems are named by their color. The impurities in beryl can be determined using various analytical techniques. Neutron activation analysis (NAA) is a sensitive technique for multielement analysis of geological samples. Four beryl samples, collected from Nayakund Mehandi Block, Parseoni, Maharashtra, were received from Geological Survey of India (GSI), Pune. Powdered samples (50-100 mg) along with comparators (IAEA Soil-7) were packed in aluminum foils, sealed in an aluminum container and irradiated for 7 days in tray rod facility of Dhruva reactor, BARC, Mumbai. After irradiation, samples were brought to laboratory. Samples were opened, transferred into polyethylene packets and weighed. Gamma activity measurements were carried out using 45% HPGe detector coupled to 8 k multi channel analyzer. For the determination of manganese, which produces relatively shorter lived activation product ( 56 Mn: T 1/2 = 2.56 h), samples were sealed in polyethylene pouches and irradiated in graphite reflector position of Critical facility reactor, BARC, Mumbai. Relative method of NAA was used for concentration calculations. IAEA reference material (RM), SL -1 (lake sediment) was analyzed for quality control. Percentage errors on the measured concentrations of the elements are within ± 8% with respect to the recommended/information values

Application of HPLC with ELSD Detection for the Assessment of Azelaic Acid Impurities in Liposomal Formulation

Directory of Open Access Journals (Sweden)

Stanislaw Han

2013-01-01

Full Text Available In the course of research and development of a new pharmaceutical formulation of azelaic acid in the liposomal form, we developed a rapid and accurate method for the detection of impurities using high-performance liquid chromatography. A chromatographic column from Merck (Purospher Star RP C18, 250–4 mm (5 μm was used in the assay, and the mobile phase gradient consisted of three phases: A—methanol : water (5 : 95 + 1.5% (v/v acetic acid; B—water : methanol (5 : 95 + 1.5% (v/v acetic acid; and C—chloroform. Detection of the impurities and the active substance was performed by an evaporative light-scattering detector. The method was validated for selectivity, system precision, method precision, limit of detection, and response rates. The proposed method can be used to detect impurities in the liposomal formulation of azelaic acid. The method enables separation of azelaic acid from the identified and unidentified impurities and from the excipients used in the drug form.

Thermally and photostimulated charge transfer on impurities and intrinsic defects in YAlO3

International Nuclear Information System (INIS)

Akkerman, V.A.; Bulka, G.P.; Vanshtejn, D.I.

1989-01-01

Methods of ESR and thermostimulated luminescence (TSL) were used to study thermo- and photostimulated change of valent state of impurity ions of iron, chromium and oxygen centers in YAlO 3 (YA). On the basis of recovery of ESR O 2 - intensity after pulsed irradiation it was established, that autolocalized holes (ALH) were mobile above 150 K with 0.54 eV activation energy. It is proposed that decay of autolocalized excitons (ALE) in YA is conditioned by thermal mobility of the hole component of ALE. Relationship of TSL with ESL data and results of high-temperature annealing of crystals in vacuum and in the air is discussed

Scattering Theory on Surface Majorana Fermions by an Impurity in ^{3}He-B.

Science.gov (United States)

Tsutsumi, Yasumasa

2017-04-07

We have formulated the scattering theory on Majorana fermions emerging in the surface bound state of the superfluid ^{3}He B phase (^{3}He-B) by an impurity. By applying the theory to the electron bubble, which is regarded as the impurity, trapped below a free surface of ^{3}He-B, the observed mobility of the electron bubble [J. Phys. Soc. Jpn. 82, 124607 (2013)JUPSAU0031-901510.7566/JPSJ.82.124607] is quantitatively reproduced. The mobility is suppressed in low temperatures from the expected value in the bulk ^{3}He-B by the contribution from the surface Majorana fermions. By contrast, the mobility does not depend on the trapped depth of the electron bubble in spite of the spatial variation of the wave function of the surface Majorana fermions. Our formulated theory demonstrates the depth-independent mobility by considering intermediate states in the scattering process. Therefore, we conclude that the experiment has succeeded in observing Majorana fermions in the surface bound state.

Neutron activation of microspheres containing 165Ho: theoretical and experimental radionuclidic impurities study

International Nuclear Information System (INIS)

Squair, Peterson L.; Pozzo, Lorena; Ivanov, Evandro; Osso Junior, Joao A.

2011-01-01

The 166 Ho microspheres are potentially interesting for medical applications for treatment of many tumors. The internal radionuclide therapy can use polymer or glass device that provides structural support for the radionuclide. After activation, beta minus emission of 166 Ho (T 1/2 =26.8h, β - E max =1.84 MeV, γ E p =80.6 keV) can be used for therapeutic purposes. The aim of this work is study the influence of radionuclide impurities between End of Bombardment (EOB) and the medical application. The appropriate specific activities and purity along decay should be adequate for their safe and efficient medical applications. The good practices on neutron activation techniques are choice a high purity target to avoid production of undesirable radionuclides and when possible with enriched targets to obtain higher specific activity. In this work the target used was Ho 2 O 3 and polymeric microspheres containing holmium acetylacetonate (HoAcAc) manufactured at the Biotechnology Center-IPEN/CNEN-SP. Three conditions were evaluated: preliminary test with 1.0x10 13 n.cm -2 s -1 for 1.0 hour; nowadays maximum capability of IEA-R1 reactor with 5.0x10 13 n.cm -2 s -1 for 64.0 hours and the ideal IEA-R1 operation with 5.0x10 13 n.cm -2 s -1 for 120.0 hours. Considering the sample with 99.9% 165 Ho purity and 0.1% for each impurities elements with its natural abundance, the highest radionuclidic impurity is the Lutetium followed by Ytterbium, Lanthanum and Cerium. The intrinsic radionuclidic impurity of 166 mHo is less relevant. This review is important to identify the radionuclidic purity characteristics of the preliminary studies with different time and flux irradiation. The data produced in this paper will help to define strategies for the production of 166 Ho radioisotope at IEA-R1 IPEN/CNEN-SP reactor. (author)

Impurities in radioactive solutions for gamma spectroscopy

International Nuclear Information System (INIS)

Delgado, J.U.

1990-01-01

The absolute and relative methods for radioactive sources calibration, like 4 Πβ-γ and 4Πγ ionization chamber respectively, allows to reach 0,1% of exactiness in activity measurement, but cannot distinguish radioactive impurities that interfere in the activity. Then, one of the problems associated to a quality control of calibrated sources furnished to users is the identification and quantification of the impurities. In this work, a routine technical procedure, using the facilities of gamma spectrometry method that allows to identify and to determine the impurities relative contribution to the source main radionuclide activity, is described. (author) [pt

Fermi-edge transmission resonance in graphene driven by a single Coulomb impurity.

Science.gov (United States)

Karnatak, Paritosh; Goswami, Srijit; Kochat, Vidya; Pal, Atindra Nath; Ghosh, Arindam

2014-07-11

The interaction between the Fermi sea of conduction electrons and a nonadiabatic attractive impurity potential can lead to a power-law divergence in the tunneling probability of charge through the impurity. The resulting effect, known as the Fermi edge singularity (FES), constitutes one of the most fundamental many-body phenomena in quantum solid state physics. Here we report the first observation of FES for Dirac fermions in graphene driven by isolated Coulomb impurities in the conduction channel. In high-mobility graphene devices on hexagonal boron nitride substrates, the FES manifests in abrupt changes in conductance with a large magnitude ≈e(2)/h at resonance, indicating total many-body screening of a local Coulomb impurity with fluctuating charge occupancy. Furthermore, we exploit the extreme sensitivity of graphene to individual Coulomb impurities and demonstrate a new defect-spectroscopy tool to investigate strongly correlated phases in graphene in the quantum Hall regime.

Radiation-stimulated yield of an impurity into interstitial sites in crystals KBr-Li and KCl-Li

International Nuclear Information System (INIS)

Bekeshev, A.Z.; Shunkeev, K.Sh.; Vasil'chenko, E.A.; Dauletbekova, A.K.; Ehlango, A.A.

1996-01-01

KCl and KBr crystals are taken as examples to show that the presence of Li impurity at X-radiation at temperatures above 200 K stimulates the creation of both impurity Hal 3 - (Li)-centers (V 4A -centers) and Hal 3 - centers (V 2 -centers). Increase of impurity concentration and X-radiation temperature (up to 300 K) results to increase of impurity stimulated creation of inherent Hal 3 - centers by more, than one order, as compared to pure crystals. Initial temperature of interstitial ion mobility was evaluated (about 140 K). 16 refs., 5 figs

Quantification of active pharmaceutical ingredient and impurities in sildenafil citrate obtained from the Internet.

Science.gov (United States)

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

Analysis of mobile ionic impurities in polyvinylalcohol thin films by thermal discharge current and dielectric impedance spectroscopy

Directory of Open Access Journals (Sweden)

M. Egginger

2012-12-01

Full Text Available Polyvinylalcohol (PVA is a water soluble polymer frequently applied in the field of organic electronics for insulating thin film layers. By-products of PVA synthesis are sodium acetate ions which contaminate the polymer material and can impinge on the electronic performance when applied as interlayer dielectrics in thin film transistors. Uncontrollable voltage instabilities and unwanted hysteresis effects are regularly reported with PVA devices. An understanding of these effects require knowledge about the electronic dynamics of the ionic impurities and their influence on the dielectric properties of PVA. Respective data, which are largely unknown, are being presented in this work. Experimental investigations were performed from room temperature to 125°C on drop-cast PVA films of three different quality grades. Data from thermal discharge current (TDC measurements, polarization experiments, and dielectric impedance spectroscopy concurrently show evidence of mobile ionic carriers. Results from TDC measurements indicate the existence of an intrinsic, build-in electric field of pristine PVA films. The field is caused by asymmetric ionic double layer formation at the two different film-interfaces (substrate/PVA and PVA/air. The mobile ions cause strong electrode polarization effects which dominate dielectric impedance spectra. From a quantitative electrode polarization analysis of isothermal impedance spectra temperature dependent values for the concentration, the mobility and conductivity together with characteristic relaxation times of the mobile carriers are given. Also shown are temperature dependent results for the dc-permittivity and the electronic resistivity. The obtained results demonstrate the feasibility to partly remove contaminants from a PVA solution by dialysis cleaning. Such a cleaning procedure reduces the values of ion concentration, conductivity and relaxation frequency.

Variational method for magnetic impurities in metals: impurity pairs

Energy Technology Data Exchange (ETDEWEB)

Oles, A M [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany, F.R.); Chao, K A [Linkoeping Univ. (Sweden). Dept. of Physics and Measurement Technology

1980-01-01

Applying a variational method to the generalized Wolff model, we have investigated the effect of impurity-impurity interaction on the formation of local moments in the ground state. The direct coupling between the impurities is found to be more important than the interaction between the impurities and the host conduction electrons, as far as the formation of local moments is concerned. Under certain conditions we also observe different valences on different impurities.

Moessbauer Studies of Implanted Impurities in Solids

CERN Multimedia

2002-01-01

Moessbauer studies were performed on implanted radioactive impurities in semiconductors and metals. Radioactive isotopes (from the ISOLDE facility) decaying to a Moessbauer isotope were utilized to investigate electronic and vibrational properties of impurities and impurity-defect structures. This information is inferred from the measured impurity hyperfine interactions and Debye-Waller factor. In semiconductors isoelectronic, shallow and deep level impurities have been implanted. Complex impurity defects have been produced by the implantation process (correlated damage) or by recoil effects from the nuclear decay in both semiconductors and metals. Annealing mechanisms of the defects have been studied. \\\\ \\\\ In silicon amorphised implanted layers have been recrystallized epitaxially by rapid-thermal-annealing techniques yielding highly supersaturated, electrically-active donor concentrations. Their dissolution and migration mechanisms have been investigated in detail. The electronic configuration of Sb donors...

Development and validation of a reversed phase liquid chromatographic method for analysis of oxytetracycline and related impurities.

Science.gov (United States)

Kahsay, Getu; Shraim, Fairouz; Villatte, Philippe; Rotger, Jacques; Cassus-Coussère, Céline; Van Schepdael, Ann; Hoogmartens, Jos; Adams, Erwin

2013-03-05

A simple, robust and fast high-performance liquid chromatographic method is described for the analysis of oxytetracycline and its related impurities. The principal peak and impurities are all baseline separated in 20 min using an Inertsil C₈ (150 mm × 4.6 mm, 5 μm) column kept at 50 °C. The mobile phase consists of a gradient mixture of mobile phases A (0.05% trifluoroacetic acid in water) and B (acetonitrile-methanol-tetrahydrofuran, 80:15:5, v/v/v) pumped at a flow rate of 1.3 ml/min. UV detection was performed at 254 nm. The developed method was validated for its robustness, sensitivity, precision and linearity in the range from limit of quantification (LOQ) to 120%. The limits of detection (LOD) and LOQ were found to be 0.08 μg/ml and 0.32 μg/ml, respectively. This method allows the separation of oxytetracycline from all known and 5 unknown impurities, which is better than previously reported in the literature. Moreover, the simple mobile phase composition devoid of non-volatile buffers made the method suitable to interface with mass spectrometry for further characterization of unknown impurities. The developed method has been applied for determination of related substances in oxytetracycline bulk samples available from four manufacturers. The validation results demonstrate that the method is reliable for quantification of oxytetracycline and its impurities. Copyright © 2012 Elsevier B.V. All rights reserved.

Metal impurities profile in a 450kg multi-crystalline silicon ingot by Cold Neutron Prompt Gamma-ray Activation Analysis

International Nuclear Information System (INIS)

Baek, Hani; Sun, Gwang Min; Kim, Ji seok; Oh, Mok; Chung, Yong Sam; Moon, Jong Hwa; Kim, Sun Ha; Baek, Sung Yeol; Tuan, Hoang Sy Minh

2014-01-01

Metal impurities are harmful to multi-crystalline silicon solar cells. They reduce solar cell conversion efficiencies through increased carrier recombination. They are present as isolated point-like impurities or precipitates. This work is to study the concentration profiles of some metal impurities of the directionally solidified 450kg multi-crystalline silicon ingot grown for solar cell production. The concentration of such impurities are generally below 10 15 cm -3 , and as such cannot be detected by physical techniques such as secondary-ion-mass spectroscopy(SIMS). So, we have tried to apply Cold Neutron - Prompt Gamma ray Activation Analysis(CN-PGAA) at the HANARO reactor research. The impurity concentrations of Au, Mn, Pt, Mo of a photovoltaic grade multi-crystalline silicon ingot appear by segregation from the liquid to the solid phase in the central region of the ingot during the crystallization. In the impurities concentration of the bottom region is higher than middle region due to the solid state diffusion. Towards the top region the segregation impurities diffused, during cooling process

Determination of Propionylbrassinolide and Its Impurities by High-Performance Liquid Chromatography with Evaporative Light Scattering Detection

Directory of Open Access Journals (Sweden)

Lidong Cao

2018-02-01

Full Text Available The discovery of brassinolide in 1979, a milestone in brassinosteroids research, has sparked great interest of brassinolide analogs (BLs in agricultural applications. Among these BLs, propionylbrassinolide has captured considerable attention because it shows plant growth regulating activity with an excellent durability. Two impurities of propionylbrassinolide were isolated and purified by semi-preparative high-performance liquid chromatography (HPLC, and the chemical structures were confirmed. For simultaneous separation and determination of propionylbrassinolide and impurities, an efficient analytical method based on HPLC with evaporative light scattering detector (HPLC-ELSD was developed. The optimized analysis was performed on a C18 reversed phase column (250 mm × 4.60 mm, 5 μm with isocratic elution of acetonitrile and water (90:10, v/v as the mobile phase. The drift tube temperature of the ELSD system was set to 50 °C and the auxiliary gas pressure was 150 kPa. The regression equations demonstrated a good linear relationship (R2 = 0.9989–0.9999 within the test ranges. The limits of detection (LODs and quantification (LOQs for propionylbrassinolide, impurity 1 and 2 were 1.3, 1.2, 1,3 and 4.3, 4.0, 4.2 mg/L, respectively. The fully validated HPLC-ELSD method was readily applied to quantify the active ingredient and impurities in propionylbrassinolide technical concentrate. Moreover, the optimized separation conditions with ELSD have been successfully transferred to mass spectrometry (MS detector for LC-MS determination.

Development and validation of a rapid chromatographic method for the analysis of flunarizine and its main production impurities

Directory of Open Access Journals (Sweden)

Niamh O’Connor

2013-06-01

Full Text Available A rapid selective method for the analysis of flunarizine and its associated impurities was developed and validated according to ICH guidelines. The separation was carried out using a Thermo Scientific Hypersil Gold C18 column (50mm×4.6mm i.d., 1.9μm particle size with a gradient mobile phase of acetonitrile–ammonium acetate–tetrabutylammoniumhydrogen sulfate buffer, at a flow rate of 1.8mL/min and UV detection at 230nm. Naturally aged samples were also tested to determine sample stability. A profile of sample and impurity breakdown was also presented. Keywords: Flunarizine, Sub 2μm column, Active pharmaceutical ingredient, HPLC

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.

Science.gov (United States)

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

Effects of Thickness of a Low-Temperature Buffer and Impurity Incorporation on the Characteristics of Nitrogen-polar GaN.

Science.gov (United States)

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.

Toward Mobile-Assisted Language Learning (MALL: Reaping Mobile Phone Benefits in Classroom Activities

Directory of Open Access Journals (Sweden)

Rully Yudhiantara

2017-07-01

Full Text Available Mobile phone has been studied by researchers in its connection with education-related activies.  This study was aimed at investigating two research questions: 1 what are students’ perception toward mobile phone to support classroom activities; 2 How do students experience mobile phone use to support classoom activities? This study employed qualitative method. To collect data, there were some technique used: questionnaire and observation.  Students participated in this study were 70 students. Findings showed that student had positive perception and attitude toward mobile phone to support classroom activities. In classroom they used mobile phone to support classroom activitis. Reading E-Book that support subject, playing Audio and Video File, operating offline dictionary were activities supported by mobile phone use.

Utilization of Photochemically Induced Fluorescence Detection for HPLC Determination of Genotoxic Impurities in the Vortioxetine Manufacturing Process.

Science.gov (United States)

Douša, Michal; Doubský, Jan; Srbek, Jan

2016-07-01

An analytical reversed-phase high-performance liquid chromatography (HPLC) method for the detection and quantitative determination of two genotoxic impurities at ppm level present in the vortioxetine manufacturing process is described. Applying the concept of threshold of toxicological concern, a limit of 75 ppm each for both genotoxic impurities was calculated based on the maximum daily dose of active pharmaceutical ingredients. The novel reversed-phase HPLC method with photochemically induced fluorescence detection was developed on XSELECT Charged Surface Hybrid Phenyl-Hexyl column using the mobile phase consisted a mixture of 10 mM ammonium formate pH 3.0 and acetonitrile. The elution was performed using an isocratic composition of 48:52 (v/v) at a flow rate of 1.0 mL/min. The photochemically induced fluorescence detection is based on the use of UV irradiation at 254 nm through measuring the fluorescence intensity at 300 nm and an excitation wavelength of 272 nm to produce fluorescent derivatives of both genotoxic impurities. The online photochemical conversion and detection is easily accomplished for two expected genotoxic impurities and provides a sufficiently low limit detection and quantification for the target analysis. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Electron-electron scattering and mobilities in semiconductors and quantum wells

International Nuclear Information System (INIS)

Lyo, S.K.

1986-01-01

The effect of electron-electron scattering on the mobility in semiconductors and semiconductor quantum wells is examined. A general exact formula is derived for the mobility, when the electron-electron collision rate is much faster than other scattering rates such as those by ionized impurities and phonons. In this limit, the transport relaxation rate is independent of the carrier's energy and contributions to the inverse mobility from individual scattering mechanism add up. The mobility becomes significantly reduced from its value in the absence of electron-electron scattering. When the collision rates are not necessarily dominated by electron-electron scattering, the mobility is calculated by the Kohler-Sondheimer variational method in the presence of ionized-impurity scattering and acoustic-phonon scattering in a nondegenerate two-dimensional quantum well

[Impurity removal technology of Tongan injection in liquid preparation process].

Science.gov (United States)

Yang, Xu-fang; Wang, Xiu-hai; Bai, Wei-rong; Kang, Xiao-dong; Liu, Jun-chao; Wu, Yun; Xiao, Wei

2015-08-01

In order to effectively remove the invalid impurities in Tongan injection, optimize the optimal parameters of the impurity removal technology of liquid mixing process, in this paper, taking Tongan injection as the research object, with the contents of celandine alkali, and sinomenine, solids reduction efficiency, and related substances inspection as the evaluation indexes, the removal of impurities and related substances by the combined process of refrigeration, coction and activated carbon adsorption were investigated, the feasibility of the impurity removal method was definited and the process parameters were optimized. The optimized process parameters were as follows: refrigerated for 36 h, boiled for 15 min, activated carbon dosage of 0.3%, temperature 100 degrees C, adsorption time 10 min. It can effectively remove the tannin, and other impurities, thus ensure the quality and safety of products.

Physical Activity Helps Seniors Stay Mobile

Science.gov (United States)

... Subscribe July 2014 Print this issue Health Capsule Physical Activity Helps Seniors Stay Mobile En español Send us your comments A carefully structured, moderate physical activity program helped vulnerable older people maintain their mobility. ...

The Consultancy Activity on In Silico Models for Genotoxic Prediction of Pharmaceutical Impurities.

Science.gov (United States)

Pavan, Manuela; Kovarich, Simona; Bassan, Arianna; Broccardo, Lorenza; Yang, Chihae; Fioravanzo, Elena

2016-01-01

The toxicological assessment of DNA-reactive/mutagenic or clastogenic impurities plays an important role in the regulatory process for pharmaceuticals; in this context, in silico structure-based approaches are applied as primary tools for the evaluation of the mutagenic potential of the drug impurities. The general recommendations regarding such use of in silico methods are provided in the recent ICH M7 guideline stating that computational (in silico) toxicology assessment should be performed using two (Q)SAR prediction methodologies complementing each other: a statistical-based method and an expert rule-based method.Based on our consultant experience, we describe here a framework for in silico assessment of mutagenic potential of drug impurities. Two main applications of in silico methods are presented: (1) support and optimization of drug synthesis processes by providing early indication of potential genotoxic impurities and (2) regulatory evaluation of genotoxic potential of impurities in compliance with the ICH M7 guideline. Some critical case studies are also discussed.

Dynamic behavior of impurities and native components in model LSM microelectrodes on YSZ

DEFF Research Database (Denmark)

Norrman, Kion; Hansen, Karin Vels; Jacobsen, Torben

2015-01-01

behavior of the native components (La, Sr, Mn) and selected impurities (Si, K, Na) both laterally and in-depth. Manganese was found to be especially mobile and showed both segregation onto the electrolyte as a result of temperature and polarization and dissolution into the electrolyte below...

The determination of some impurities in zirconium metal by instrumental neutron activation analysis

International Nuclear Information System (INIS)

Eddy, B.T.; Pearton, D.C.G.; Watterson, J.J.

1976-01-01

This report describes the work done on the development of an instrumental neutron-activation method for the analysis of impurities in reactor-grade zirconium. Nine samples were analysed, and the results were compared with those obtained by other techniques. No statistically significant differences were observed for ten of the twelve elements that could possibly be determined by instrumental neutron-activation analysis. Cadmium cannot be determined at the 0,5 p.p.m. level, and there is doubt about the comparative values recorded for aluminium. The precision of the measurement by direct instrumental neutron-activation analysis ranges from 1,4 per cent for tungsten to 17 per cent for chromium [af

Trace impurity analyzer

International Nuclear Information System (INIS)

Schneider, W.J.; Edwards, D. Jr.

1979-01-01

The desirability for long-term reliability of large scale helium refrigerator systems used on superconducting accelerator magnets has necessitated detection of impurities to levels of a few ppM. An analyzer that measures trace impurity levels of condensable contaminants in concentrations of less than a ppM in 15 atm of He is described. The instrument makes use of the desorption temperature at an indicated pressure of the various impurities to determine the type of contaminant. The pressure rise at that temperature yields a measure of the contaminant level of the impurity. A LN 2 cryogenic charcoal trap is also employed to measure air impurities (nitrogen and oxygen) to obtain the full range of contaminant possibilities. The results of this detector which will be in use on the research and development helium refrigerator of the ISABELLE First-Cell is described

Determination of oxygen impurity in high purity materials by charged particle activation analysis using alpha projectiles

International Nuclear Information System (INIS)

Chowdhury, D.P.; Pal, S.; Arunachalam, J.; Verma R.; Gangadharan, S.

1992-01-01

40 MeV α-particles have been used to determine oxygen impurity at ppm levels in silicon, copper, and stainless steel, through the radiochemical separation of 18 F from the matrix. The separation of 18 F has been carried out by two techniques, viz. distillation of H 2 SiF 6 and precipitation of KBF 4 and some modification has been applied in the separation, depending on the nature of interferences from the matrix. Instrumental approach was also carried out to determine the oxygen impurity at ≥ 100 ppm in Si matrix because this approach is not possible in Cu and stainless steel samples due to matrix activity. (author) 10 refs.; 1 fig.; 5 tabs

Electron mobility in monoclinic β-Ga2O3—Effect of plasmon-phonon coupling, anisotropy, and confinement

Science.gov (United States)

Ghosh, Krishnendu; Singisetti, Uttam

2017-11-01

This work reports an investigation of electron transport in monoclinic \\beta-Ga2O3 based on a combination of density functional perturbation theory based lattice dynamical computations, coupling calculation of lattice modes with collective plasmon oscillations and Boltzmann theory based transport calculations. The strong entanglement of the plasmon with the different longitudinal optical (LO) modes make the role LO-plasmon coupling crucial for transport. The electron density dependence of the electron mobility in \\beta-Ga2O3 is studied in bulk material form and also in the form of two-dimensional electron gas. Under high electron density a bulk mobility of 182 cm2/ V.s is predicted while in 2DEG form the corresponding mobility is about 418 cm2/V.s when remote impurities are present at the interface and improves further as the remote impurity center moves away from the interface. The trend of the electron mobility shows promise for realizing high electron mobility in dopant isolated electron channels. The experimentally observed small anisotropy in mobility is traced through a transient Monte Carlo simulation. It is found that the anisotropy of the IR active phonon modes is responsible for giving rise to the anisotropy in low-field electron mobility.

Neutron activation determination of impurities in high-purity bismuth with separation of matrix in form of hydroxide

International Nuclear Information System (INIS)

Artyukhin, P.I.; Shavinskij, B.M.; Mityakin, Yu.L.

1979-01-01

The technique of neutron activation determination of 15 impurity elements (Au, Ag, Ba, Cd, Co, Cs, Cu, Hg, K, Na, Ni, Se, Sr, Te, Zn) in high-purity bismuth (impurity content is approximately 10 -6 -10 -10 %) is presented. Bismuth hydroxide precipitation by ammonia from nitric acid solutions was used to separate bismuth from alkali, alkaline earth metals and elements forming stable ammines. Gold, selenium and tellurium are isolated in the form of metals at reduction by muriatic hydrazine. Results of analyzing two samples of special purity bismuth are presented. Neutron flux comprised 0.8-1x10 13 n/cm 2 xs. Radiation time was equal to 90 hours

Recent trends in the impurity profile of pharmaceuticals

Directory of Open Access Journals (Sweden)

Kavita Pilaniya

2010-01-01

Full Text Available Various regulatory authorities such as the International Conference on Harmonization (ICH, the United States Food and Drug administration (FDA, and the Canadian Drug and Health Agency (CDHA are emphasizing on the purity requirements and the identification of impurities in Active Pharmaceutical Ingredients (APIs. The various sources of impurity in pharmaceutical products are - reagents, heavy metals, ligands, catalysts, other materials like filter aids, charcoal, and the like, degraded end products obtained during \\ after manufacturing of bulk drugs from hydrolysis, photolytic cleavage, oxidative degradation, decarboxylation, enantiomeric impurity, and so on. The different pharmacopoeias such as the British Pharmacopoeia, United State Pharmacopoeia, and Indian Pharmacopoeia are slowly incorporating limits to allowable levels of impurities present in APIs or formulations. Various methods are used to isolate and characterize impurities in pharmaceuticals, such as, capillary electrophoresis, electron paramagnetic resonance, gas-liquid chromatography, gravimetric analysis, high performance liquid chromatography, solid-phase extraction methods, liquid-liquid extraction method, Ultraviolet Spectrometry, infrared spectroscopy, supercritical fluid extraction column chromatography, mass spectrometry, Nuclear magnetic resonance (NMR spectroscopy, and RAMAN spectroscopy. Among all hyphenated techniques, the most exploited techniques for impurity profiling of drugs are Liquid Chromatography (LC-Mass Spectroscopy (MS, LC-NMR, LC-NMR-MS, GC-MS, and LC-MS. This reveals the need and scope of impurity profiling of drugs in pharmaceutical research.

Fast determination of impurities in metallurgical grade silicon for photovoltaics by instrumental neutron activation analysis

International Nuclear Information System (INIS)

Hampel, J.; Boldt, F.M.; Gerstenberg, H.; Hampel, G.; Kratz, J.V.; Reber, S.; Wiehl, N.

2011-01-01

Standard wafer solar cells are made of near-semiconductor quality silicon. This high quality material makes up a significant part of the total costs of a solar module. Therefore, new concepts with less expensive so called solar grade silicon directly based on physiochemically upgraded metallurgical grade silicon are investigated. Metallurgical grade silicon contains large amounts of impurities, mainly transition metals like Fe, Cr, Mn, and Co, which degrade the minority carrier lifetime and thus the solar cell efficiency. A major reduction of the transition metal content occurs during the unidirectional crystallization due to the low segregation coefficient between the solid and liquid phase. A further reduction of the impurity level has to be done by gettering procedures applied to the silicon wafers. The efficiency of such cleaning procedures of metallurgical grade silicon is studied by instrumental neutron activation analysis (INAA). Small sized silicon wafers of approximately 200 mg with and without gettering step were analyzed. To accelerate the detection of transition metals in a crystallized silicon ingot, experiments of scanning whole vertical silicon columns with a diameter of approximately 1 cm by gamma spectroscopy were carried out. It was demonstrated that impurity profiles can be obtained in a comparably short time. Relatively constant transition metal ratios were found throughout an entire silicon ingot. This led to the conclusion that the determination of several metal profiles might be possible by the detection of only one 'leading element'. As the determination of Mn in silicon can be done quite fast compared to elements like Fe, Cr, and Co, it could be used as a rough marker for the overall metal concentration level. Thus, a fast way to determine impurities in photovoltaic silicon material is demonstrated. - Highlights: → We demonstrate a fast way to determine impurities in photovoltaic silicon by NAA. → We make first experiments of locally

An investigation of the impurities in native gold by neutron-activation analysis

International Nuclear Information System (INIS)

Erasmus, C.S.; Sellschop, J.P.F.; Hallbauer, D.K.; Novak, E.

1980-01-01

Instrumental and radiochemical methods of neutron-activation analysis, developed for the determination of major, minor, and trace impurities in native gold, are described. The gold was obtained from Witwatersrand reefs and from deposits in the Barberton area. It was extracted by decomposition of the ore in cold hydrofluoric acid. Quantitative results are presented for 14 elements found in native gold, and the significance of these elements in relation to the distribution of gold is discussed. The results suggest that there are geochemical differences in native gold from various reefs and deposits

Toward Mobile-Assisted Language Learning (MALL): Reaping Mobile Phone Benefits in Classroom Activities

OpenAIRE

Rully Yudhiantara; Ihsan Abdul Nasir

2017-01-01

Mobile phone has been studied by researchers in its connection with education-related activies. This study was aimed at investigating two research questions: 1) what are students' perception toward mobile phone to support classroom activities; 2) How do students experience mobile phone use to support classoom activities? This study employed qualitative method. To collect data, there were some technique used: questionnaire and observation. Students participated in this study were 70 students...

Mobility in n-doped wurtzite III-Nitrides

Directory of Open Access Journals (Sweden)

C.G. Rodrigues

2003-01-01

Full Text Available A study of the mobility of n-doped wurtzite III-Nitrides is reported. We have determined the nonequilibrium thermodynamic state of the III-Nitrides systems driven far away from equilibrium by a strong electric field in the steady state, which follows after a very fast transient. The dependence of the mobility (which depends on the nonequilibrium thermodynamic state of the sample on the electric field strength is derived, which decreases with the strength of electric field. We analyzed the contributions to the mobility arising out of the different channels of electron scattering, namely, the polar optic, deformation, piezoelectric, interactions with the phonons, and with impurities. The case of n-InN, n-GaN, and n-AlN have been analyzed: as expected the main contribution comes from the polar-optic interactions in these strongly polar semiconductors. The other interactions are in decreasing order, the deformation acoustic, the piezoelectric, and the one due to impurities.

Integrable quantum impurity models

International Nuclear Information System (INIS)

Eckle, H.P.

1998-01-01

By modifying some of the local L operators of the algebraic form of the Bethe Ansatz inhomogeneous one dimensional quantum lattice models can be constructed. This fact has recently attracted new attention, the inhomogeneities being interpreted as local impurities. The Hamiltonians of the so constructed one-dimensional quantum models have a nearest neighbour structure except in the vicinity of the local impurities which involve three-site interactions. The pertinent feature of these models is the absence of backscattering at the impurities: the impurities are transparent. (Copyright (1998) World Scientific Publishing Co. Pte. Ltd)

Mobile Phone Chips Reduce Increases in EEG Brain Activity Induced by Mobile Phone-Emitted Electromagnetic Fields

Science.gov (United States)

Henz, Diana; Schöllhorn, Wolfgang I.; Poeggeler, Burkhard

2018-01-01

Recent neurophysiological studies indicate that exposure to electromagnetic fields (EMFs) generated by mobile phone radiation can exert effects on brain activity. One technical solution to reduce effects of EMFs in mobile phone use is provided in mobile phone chips that are applied to mobile phones or attached to their surfaces. To date, there are no systematical studies on the effects of mobile phone chip application on brain activity and the underlying neural mechanisms. The present study investigated whether mobile phone chips that are applied to mobile phones reduce effects of EMFs emitted by mobile phone radiation on electroencephalographic (EEG) brain activity in a laboratory study. Thirty participants volunteered in the present study. Experimental conditions (mobile phone chip, placebo chip, no chip) were set up in a randomized within-subjects design. Spontaneous EEG was recorded before and after mobile phone exposure for two 2-min sequences at resting conditions. During mobile phone exposure, spontaneous EEG was recorded for 30 min during resting conditions, and 5 min during performance of an attention test (d2-R). Results showed increased activity in the theta, alpha, beta and gamma bands during EMF exposure in the placebo and no chip conditions. Application of the mobile phone chip reduced effects of EMFs on EEG brain activity and attentional performance significantly. Attentional performance level was maintained regarding number of edited characters. Further, a dipole analysis revealed different underlying activation patterns in the chip condition compared to the placebo chip and no chip conditions. Finally, a correlational analysis for the EEG frequency bands and electromagnetic high-frequency (HF) emission showed significant correlations in the placebo chip and no chip condition for the theta, alpha, beta, and gamma bands. In the chip condition, a significant correlation of HF with the theta and alpha bands, but not with the beta and gamma bands was

Mobile Phone Chips Reduce Increases in EEG Brain Activity Induced by Mobile Phone-Emitted Electromagnetic Fields.

Science.gov (United States)

Henz, Diana; Schöllhorn, Wolfgang I; Poeggeler, Burkhard

2018-01-01

Recent neurophysiological studies indicate that exposure to electromagnetic fields (EMFs) generated by mobile phone radiation can exert effects on brain activity. One technical solution to reduce effects of EMFs in mobile phone use is provided in mobile phone chips that are applied to mobile phones or attached to their surfaces. To date, there are no systematical studies on the effects of mobile phone chip application on brain activity and the underlying neural mechanisms. The present study investigated whether mobile phone chips that are applied to mobile phones reduce effects of EMFs emitted by mobile phone radiation on electroencephalographic (EEG) brain activity in a laboratory study. Thirty participants volunteered in the present study. Experimental conditions (mobile phone chip, placebo chip, no chip) were set up in a randomized within-subjects design. Spontaneous EEG was recorded before and after mobile phone exposure for two 2-min sequences at resting conditions. During mobile phone exposure, spontaneous EEG was recorded for 30 min during resting conditions, and 5 min during performance of an attention test (d2-R). Results showed increased activity in the theta, alpha, beta and gamma bands during EMF exposure in the placebo and no chip conditions. Application of the mobile phone chip reduced effects of EMFs on EEG brain activity and attentional performance significantly. Attentional performance level was maintained regarding number of edited characters. Further, a dipole analysis revealed different underlying activation patterns in the chip condition compared to the placebo chip and no chip conditions. Finally, a correlational analysis for the EEG frequency bands and electromagnetic high-frequency (HF) emission showed significant correlations in the placebo chip and no chip condition for the theta, alpha, beta, and gamma bands. In the chip condition, a significant correlation of HF with the theta and alpha bands, but not with the beta and gamma bands was

Influence of complex impurity centres on radiation damage in wide-gap metal oxides

Energy Technology Data Exchange (ETDEWEB)

Lushchik, A., E-mail: aleksandr.lushchik@ut.ee [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Lushchik, Ch. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Popov, A.I. [Institute of Solid State Physics, University of Latvia, Kengaraga 8, Riga LV-1063 (Latvia); Schwartz, K. [GSI Helmholtzzentrum für Schwerionenforschung (GSI), Planckstr. 1, 64291 Darmstadt (Germany); Shablonin, E.; Vasil’chenko, E. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia)

2016-05-01

Different mechanisms of radiation damage of wide-gap metal oxides as well as a dual influence of impurity ions on the efficiency of radiation damage have been considered on the example of binary ionic MgO and complex ionic–covalent Lu{sub 3}Al{sub 5}O{sub 12} single crystals. Particular emphasis has been placed on irradiation with ∼2 GeV heavy ions ({sup 197}Au, {sup 209}Bi, {sup 238}U, fluence of 10{sup 12} ions/cm{sup 2}) providing extremely high density of electronic excitations within ion tracks. Besides knock-out mechanism for Frenkel pair formation, the additional mechanism through the collapse of mobile discrete breathers at certain lattice places (e.g., complex impurity centres) leads to the creation of complex defects that involve a large number of host atoms. The experimental manifestations of the radiation creation of intrinsic and impurity antisite defects (Lu|{sub Al} or Ce|{sub Al} – a heavy ion in a wrong cation site) have been detected in LuAG and LuAG:Ce{sup 3+} single crystals. Light doping of LuAG causes a small enhancement of radiation resistance, while pair impurity centres (for instance, Ce|{sub Lu}–Ce|{sub Al} or Cr{sup 3+}–Cr{sup 3+} in MgO) are formed with a rise of impurity concentration. These complex impurity centres as well as radiation-induced intrinsic antisite defects (Lu|{sub Al} strongly interacting with Lu in a regular site) tentatively serve as the places for breathers collapse, thus decreasing the material resistance against dense irradiation.

Synthesis and Identification of Selected Impurities

Energy Technology Data Exchange (ETDEWEB)

Zhiqiang, Zhou [Department of Applied Chemistry, China Agricultural University, Beijing (China)

2009-07-15

Non-active substances undesired, but often unavoidable compounds accompanying target active ingredients in various pesticide formulations have been synthesized for supporting product registration and evaluation of the total toxicological and physicochemical properties of formulated products. The synthesis and structural characterization of various impurities of pesticide active ingredients are described and illustrated by IR, NMR, GC and GC/MS data. (author)

Mobility devices to promote activity and participation

DEFF Research Database (Denmark)

Salminen, Anna-Liisa; Brandt, Ase; Samuelsson, Kersti A M

2009-01-01

were included if they covered both baseline and follow-up data and focused on activity and participation. Study participants had to be aged over 18 years with mobility limitations. Mobility device interventions encompassed crutches, walking frames, rollators, manual wheelchairs and powered wheelchairs......, and 3 follow-up studies that included before and after data. Two studies dealt with the effects of powered wheelchair interventions and the other studies with various other types of mobility device. Two studies were of high, internal and external methodological quality. Interventions were found......OBJECTIVE: To determine the effectiveness of mobility device interventions in terms of activity and participation for people with mobility limitations. DESIGN: Systematic review. Search of 7 databases during the period 1996 to 2008. METHODS: Controlled studies and non-controlled follow-up studies...

Research on Mobile Learning Activities Applying Tablets

Science.gov (United States)

Kurilovas, Eugenijus; Juskeviciene, Anita; Bireniene, Virginija

2015-01-01

The paper aims to present current research on mobile learning activities in Lithuania while implementing flagship EU-funded CCL project on application of tablet computers in education. In the paper, the quality of modern mobile learning activities based on learning personalisation, problem solving, collaboration, and flipped class methods is…

Detection, isolation and characterization of principle synthetic route indicative impurity in telmisartan

Directory of Open Access Journals (Sweden)

V. Srinivasan

2016-11-01

Full Text Available An unknown impurity was detected in the telmisartan bulk drug (active pharmaceutical ingredient – API using an isocratic reversed-phase high performance liquid chromatography (HPLC. This impurity was isolated by preparative HPLC. Spectral data of the isolated impurity were collected. Based on the spectral data deriving from two dimensional nuclear magnetic spectroscopy (2D-NMR and mass spectrometry (MS, the impurity was characterized as “methyl 4′,4′-dibromo methyl biphenyl-2-carboxylate”. The arrived structure was further confirmed by theoretical studies.

Mobile health: a synopsis and comment on "Increasing physical activity with mobile devices: a meta-analysis".

Science.gov (United States)

Johnston, Winter; Hoffman, Sara; Thornton, Louise

2014-03-01

We offer a synopsis and commentary on J. Fanning and colleagues' article "Increasing Physical Activity with Mobile Devices: A Meta-Analysis" published in the Journal of Medical Internet Research. Although regular physical activity has a range of benefits, very few adults in the USA meet recommended guidelines for daily physical activity. The meta-analysis of Fanning et al. (2012) aimed to synthesize the results of research using mobile devices to increase physical activity. Their review identified 11 studies that used mobile technologies, including short message service (SMS), apps, or personal digital assistant (PDA) to improve physical activity behaviors among participants. Fanning et al. conclude that while literature in this area is limited to date, there is initial support for the efficacy of mobile-based interventions for improving physical activity. Included studies varied greatly, and the majority used only SMS to influence physical behaviors, meaning generalization of results to other forms of mobile technologies may be premature. This review does, however, provide a foundation for understanding how mobile-based interventions may be used efficaciously for the development of future interventions to improve health behaviors.

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

Science.gov (United States)

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.

Numerical renormalization group calculation of impurity internal energy and specific heat of quantum impurity models

Science.gov (United States)

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.

DETECTING LOW-LEVEL SYNTHESIS IMPURITIES IN MODIFIED PHOSPHOROTHIOATE OLIGONUCLEOTIDES USING LIQUID CHROMATOGRAPHY – HIGH RESOLUTION MASS SPECTROMETRY

Science.gov (United States)

Nikcevic, Irena; Wyrzykiewicz, Tadeusz K.; Limbach, Patrick A.

2010-01-01

Summary An LC-MS method based on the use of high resolution Fourier transform ion cyclotron resonance mass spectrometry (FTIRCMS) for profiling oligonucleotides synthesis impurities is described. Oligonucleotide phosphorothioatediesters (phosphorothioate oligonucleotides), in which one of the non-bridging oxygen atoms at each phosphorus center is replaced by a sulfur atom, are now one of the most popular oligonucleotide modifications due to their ease of chemical synthesis and advantageous pharmacokinetic properties. Despite significant progress in the solid-phase oligomerization chemistry used in the manufacturing of these oligonucleotides, multiple classes of low-level impurities always accompany synthetic oligonucleotides. Liquid chromatography-mass spectrometry has emerged as a powerful technique for the identification of these synthesis impurities. However, impurity profiling, where the entire complement of low-level synthetic impurities is identified in a single analysis, is more challenging. Here we present an LC-MS method based the use of high resolution-mass spectrometry, specifically Fourier transform ion cyclotron resonance mass spectrometry (FTIRCMS or FTMS). The optimal LC-FTMS conditions, including the stationary phase and mobile phases for the separation and identification of phosphorothioate oligonucleotides, were found. The characteristics of FTMS enable charge state determination from single m/z values of low-level impurities. Charge state information then enables more accurate modeling of the detected isotopic distribution for identification of the chemical composition of the detected impurity. Using this approach, a number of phosphorothioate impurities can be detected by LC-FTMS including failure sequences carrying 3′-terminal phosphate monoester and 3′-terminal phosphorothioate monoester, incomplete backbone sulfurization and desulfurization products, high molecular weight impurities, and chloral, isobutyryl, and N3 (2-cyanoethyl) adducts

A study on neutron activation analysis for the determination of the contents of impurities in reactor materials

International Nuclear Information System (INIS)

Kim, N.B.

1983-01-01

In determining the contents of impurity elements in reactor materials using neutron activation analysis, methods for preconcentration and radiochemical separtion have been studied. Before applying neutron irradiation, impurities in uranium dioxide have been preconcentrated by an anion exchange separtion method and boron impurity has been preconcentrated by a cation exchange separation method or an ashing method. After neutron irradiation the radiochemical separation method for the determination of 27 elements is based on a group separation using ion-exchange resin and material exchanger. The method has imployed mineral acid or organic mixture of the acid, excluding hydrofluoric acid, as the media and common glass wares as the apparatus. This separation method was applied to the reactor materials such as aluminum, steel, graphite and uranium dioxide. The single comparator method was used for determining the content of each element separated radiochemically and analytical results gave the statistical and systematic errors of less than 10% and 6.1%, respectively. A prompt gamma-ray measurement method has been used for determining the content of preconcentrated boron and the analytical results gave the statistical and systematic errors of 5.4% and 3.3%, respectively. (Author)

Decoupling single nanowire mobilities limited by surface scattering and bulk impurity scattering

International Nuclear Information System (INIS)

Khanal, D. R.; Levander, A. X.; Wu, J.; Yu, K. M.; Liliental-Weber, Z.; Walukiewicz, W.; Grandal, J.; Sanchez-Garcia, M. A.; Calleja, E.

2011-01-01

We demonstrate the isolation of two free carrier scattering mechanisms as a function of radial band bending in InN nanowires via universal mobility analysis, where effective carrier mobility is measured as a function of effective electric field in a nanowire field-effect transistor. Our results show that Coulomb scattering limits effective mobility at most effective fields, while surface roughness scattering only limits mobility under very high internal electric fields. High-energy α particle irradiation is used to vary the ionized donor concentration, and the observed decrease in mobility and increase in donor concentration are compared to Hall effect results of high-quality InN thin films. Our results show that for nanowires with relatively high doping and large diameters, controlling Coulomb scattering from ionized dopants should be given precedence over surface engineering when seeking to maximize nanowire mobility.

Impurity solitons with quadratic nonlinearities

DEFF Research Database (Denmark)

Clausen, Carl A. Balslev; Torres, Juan P-; Torner, Lluis

1998-01-01

We fmd families of solitary waves mediated by parametric mixing in quadratic nonlinear media that are localized at point-defect impurities. Solitons localized at attractive impurities are found to be dynamically stable. It is shown that localization at the impurity modifies strongly the soliton...

Active cooling of a mobile phone handset

International Nuclear Information System (INIS)

Grimes, Ronan; Walsh, Ed; Walsh, Pat

2010-01-01

Power dissipation levels in mobile phones continue to increase due to gaming, higher power applications, and increased functionality associated with the internet. The current cooling methodologies of natural convection and radiation limit the power dissipation within a mobile phone to between 1-2 W depending on size. As power dissipation levels increase, products such as mobile phones will require active cooling to ensure that the devices operate within an acceptable temperature envelop from both user comfort and reliability perspectives. In this paper, we focus on the applied thermal engineering problem of an active cooling solution within a typical mobile phone architecture by implementing a custom centrifugal fan within the mobile phone. Its performance is compared in terms of flow rates and pressure drops, allowable phone heat dissipation and maximum phone surface temperature as this is the user constraint for a variety of simulated PCB architectures in the mobile phone. Perforated plates with varying porosity through different size orifices are used to simulate these architectures. The results show that the power level dissipated by a phone for a constant surface temperature may be increased by ∼50 - 75% depending on pressure drop induced by the internal phone architecture. Hence for successful implementation and efficient utilization of active cooling will require chip layout to be considered at the design stage.

Some effects of MHD activity on impurity transport in the PBX tokamak

International Nuclear Information System (INIS)

Ida, K.; Fonck, R.J.; Hulse, R.A.; LeBlanc, B.

1985-10-01

The effects of MHD activity on intrinsic impurity transport are studied in ohmic discharges of the Princeton Beta Experiment (PBX) by measuring of the Z/sub eff/ profile from visible bremsstrahlung radiation and the spectral line intensities from ultraviolet spectroscopy. A diffusive/convective transport model, including an internal disruption model, is used to simulate the data. The Z/sub eff/ profile with no MHD activity is fitted with a strong inward convection, characterized by a peaking parameter c/sub v/ (= -a 2 v/2rD) = 11 (3.5, +4.5). At the onset of MHD activity (a large m = 1 n = 1 oscillation followed by sawteeth), this strongly peaked profile is flattened and subsequently reaches a new quasi-equilibrium shape. This profile is characterized by reduced convection [c/sub v/ = 3.6 (-1.1, +1.6), D = 1.4 (-0.7, +5.6) x 10 4 cm 2 /s], in addition to the particle redistribution which accompanies the sawtooth internal disruptions. 10 figs

Impurity-generated non-Abelions

Science.gov (United States)

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

Phonon-impurity relaxation and acoustic wave absorption in yttrium-aluminium garnet crystals with impurities

International Nuclear Information System (INIS)

Ivanov, S.N.; Kotelyanskij, I.M.; Medved', V.V.

1983-01-01

The experimental results of investigations of the influence of substitution impurities in the yttrium-aluminium garnet lattice on absorption of high-frequency acoustic waves are presented. It is shown that the phonon-impurity relaxation processses affect at most the wave absorption and have resonance character when the acoustic wave interacts with the thermal phonon group in the vicinity of the perturbed part of the phonon spectrum caused by the impurity. The differences of time values between inelastic and elastic thermal phonons relaxations determined from the data on longitudinal and shear waves in pure and impurity garnet crystals are discussed

Divertor experiment for impurity control in DIVA

International Nuclear Information System (INIS)

Nagami, Masayuki

1979-04-01

Divertor actions of controlling the impurities and the transport of impurity ions in the plasma have been investigated in the DIVA device. Following are the results: (1) The radial transport of impurity ions is not described only by neoclassical theory, but it is strongly influenced by anomalous process. Radial diffusion of impurity ions across the whole minor radius is well described by a neoclassical diffusion superposed by the anomalous diffusion for protons. Due to this anomalous process, which spreads the radial density profile of impurity ions, 80 to 90% of the impurity flux in the plasma outer edge is shielded even in a nondiverted discharge. (2) The divertor reduces the impurity flux entering the main plasma by a factor of 2 to 4. The impurity ions shielded by the scrape-off plasma are rapidly guided into the burial chamber with a poloidal excursion time roughly equal to that of the scrape-off plasma. (3) The divertor reduces the impurity ion flux onto the main vacuum chamber by guiding the impurity ions diffusing from the main plasma into the burial chamber, thereby reducing the plasma-wall interaction caused by diffusing impurity ions at the main vacuum chamber. The impurity ions produced in the burial chamber may flow back to the main plasma through the scrape-off layer. However, roughly only 0.3% of the impurity flux into the scrape-off plasma in the burial chamber penetrates into the main plasma due to the impurity backflow. (4) A slight cooling of the scrape-off plasma with light-impurity injection effectively reduces the metal impurity production at the first wall by reducing the potential difference between the plasma and the wall, thereby reducing the accumulation of the metal impurity in the discharge. Radiation cooling by low-Z impurities in the plasma outer edge, which may become an important feature in future large tokamaks both with and without divertor, is numerically evaluated for carbon, oxygen and neon. (author)

Interface-controlled, high-mobility organic transistors

NARCIS (Netherlands)

Jurchescu, Oana D.; Popinciuc, Mihaita; van Wees, Bart J.; Palstra, Thomas T. M.

2007-01-01

The achievement of high mobilities in field-effect transistors (FETs) is one of the main challenges for the widespread application of organic conductors in devices. Good device performance of a single-crystal pentacene FET requires both removal of impurity molecules from the bulk and the

Mobile Health Applications to Promote Active and Healthy Ageing.

Science.gov (United States)

Helbostad, Jorunn L; Vereijken, Beatrix; Becker, Clemens; Todd, Chris; Taraldsen, Kristin; Pijnappels, Mirjam; Aminian, Kamiar; Mellone, Sabato

2017-03-18

The European population is ageing, and there is a need for health solutions that keep older adults independent longer. With increasing access to mobile technology, such as smartphones and smartwatches, the development and use of mobile health applications is rapidly growing. To meet the societal challenge of changing demography, mobile health solutions are warranted that support older adults to stay healthy and active and that can prevent or delay functional decline. This paper reviews the literature on mobile technology, in particular wearable technology, such as smartphones, smartwatches, and wristbands, presenting new ideas on how this technology can be used to encourage an active lifestyle, and discusses the way forward in order further to advance development and practice in the field of mobile technology for active, healthy ageing.

Graphene plasmons: Impurities and nonlocal effects

Science.gov (United States)

Viola, Giovanni; Wenger, Tobias; Kinaret, Jari; Fogelström, Mikael

2018-02-01

This work analyzes how impurities and vacancies on the surface of a graphene sample affect its optical conductivity and plasmon excitations. The disorder is analyzed in the self-consistent Green's function formulation and nonlocal effects are fully taken into account. It is shown that impurities modify the linear spectrum and give rise to an impurity band whose position and width depend on the two parameters of our model, the density and the strength of impurities. The presence of the impurity band strongly influences the electromagnetic response and the plasmon losses. Furthermore, we discuss how the impurity-band position can be obtained experimentally from the plasmon dispersion relation and discuss this in the context of sensing.

Low Z impurity transport in tokamaks

International Nuclear Information System (INIS)

Hawryluk, R.J.; Suckewer, S.; Hirshman, S.P.

1978-10-01

Low Z impurity transport in tokamaks was simulated with a one-dimensional impurity transport model including both neoclassical and anomalous transport. The neoclassical fluxes are due to collisions between the background plasma and impurity ions as well as collisions between the various ionization states. The evaluation of the neoclassical fluxes takes into account the different collisionality regimes of the background plasma and the impurity ions. A limiter scrapeoff model is used to define the boundary conditions for the impurity ions in the plasma periphery. In order to account for the spectroscopic measurements of power radiated by the lower ionization states, fluxes due to anomalous transport are included. The sensitivity of the results to uncertainties in rate coefficients and plasma parameters in the periphery are investigated. The implications of the transport model for spectroscopic evaluation of impurity concentrations, impurity fluxes, and radiated power from line emission measurements are discussed

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

Energy Technology Data Exchange (ETDEWEB)

Kumar, S. T. A.; Den Hartog, D. J.; Mirnov, V. V.; Eilerman, S.; Nornberg, M.; Reusch, J. A.; Sarff, J. S. [Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Caspary, K. J.; Chapman, B. E.; Parke, E. [Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Magee, R. M. [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States); Brower, D. L.; Ding, W. X.; Lin, L. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095 (United States); Craig, D. [Physics Department, Wheaton College, Wheaton, Illinois 60187 (United States); Fiksel, G. [Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Laboratory for Laser Energetics, University of Rochester, Rochester, New York (United States)

2012-05-15

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.

The impurity transport in HT-6B tokamak

International Nuclear Information System (INIS)

Huang Rong; Xie Jikang; Li Linzhong; He Yexi; Wang Shuya; Deng Chuanbao; Li Guoxiang; Qiu Lijian

1992-06-01

The quasi-stationary profiles of the impurity ionization stages in HT-6B tokamak were determined by monitoring the VUV (vacuum ultraviolet) and visible line emissions from impurities. An impurity transport code was set up. The impurity transport coefficients and other parameters of impurities in that device were simulated and determined. From the measurement of impurity emission profiles and simulation analysis, it is concluded that the impurity confinement is improved and the impurity recycling is reduced by the slow magnetic compression. Some characteristics of impurity transport in that device are also discussed

Impurity gettering in semiconductors

Science.gov (United States)

Sopori, Bhushan L.

1995-01-01

A process for impurity gettering in a semiconductor substrate or device such as a silicon substrate or device. The process comprises hydrogenating the substrate or device at the back side thereof with sufficient intensity and for a time period sufficient to produce a damaged back side. Thereafter, the substrate or device is illuminated with electromagnetic radiation at an intensity and for a time period sufficient to cause the impurities to diffuse to the back side and alloy with a metal there present to form a contact and capture the impurities. The impurity gettering process also can function to simultaneously passivate defects within the substrate or device, with the defects likewise diffusing to the back side for simultaneous passivation. Simultaneously, substantially all hydrogen-induced damage on the back side of the substrate or device is likewise annihilated. Also taught is an alternate process comprising thermal treatment after hydrogenation of the substrate or device at a temperature of from about 500.degree. C. to about 700.degree. C. for a time period sufficient to cause the impurities to diffuse to the damaged back side thereof for subsequent capture by an alloying metal.

Mobile Robotics Activities in DOE Laboratories

Energy Technology Data Exchange (ETDEWEB)

Ron Lujan; Jerry Harbour; John T. Feddema; Sharon Bailey; Jacob Barhen; David Reister

2005-03-01

This paper will briefly outline major activities in Department of Energy (DOE) Laboratories focused on mobile platforms, both Unmanned Ground Vehicles (UGV’s) as well as Unmanned Air Vehicles (UAV’s). The activities will be discussed in the context of the science and technology construct used by the DOE Technology Roadmap for Robotics and Intelligent Machines (RIM)1 published in 1998; namely, Perception, Reasoning, Action, and Integration. The activities to be discussed span from research and development to deployment in field operations. The activities support customers in other agencies. The discussion of "perception" will include hyperspectral sensors, complex patterns discrimination, multisensor fusion and advances in LADAR technologies, including real-world perception. "Reasoning" activities to be covered include cooperative controls, distributed systems, ad-hoc networks, platform-centric intelligence, and adaptable communications. The paper will discuss "action" activities such as advanced mobility and various air and ground platforms. In the RIM construct, "integration" includes the Human-Machine Integration. Accordingly the paper will discuss adjustable autonomy and the collaboration of operator(s) with distributed UGV’s and UAV’s. Integration also refers to the applications of these technologies into systems to perform operations such as perimeter surveillance, large-area monitoring and reconnaissance. Unique facilities and test beds for advanced mobile systems will be described. Given that this paper is an overview, rather than delve into specific detail in these activities, other more exhaustive references and sources will be cited extensively.

GalileoMobile: Astronomical activities in schools

Science.gov (United States)

Dasi Espuig, Maria; Vasquez, Mayte; Kobel, Philippe

GalileoMobile is an itinerant science education initiative run on a voluntary basis by an international team of astronomers, educators, and science communicators. Our team's main goal is to make astronomy accessible to schools and communities around the globe that have little or no access to outreach actions. We do this by performing teacher workshops, activities with students, and donating educational material. Since the creation of GalileoMobile in 2008, we have travelled to Chile, Bolivia, Peru, India, and Uganda, and worked with 56 schools in total. Our activities are centred on the GalileoMobile Handbook of Activities that comprises around 20 astronomical activities which we adapted from many different sources, and translated into 4 languages. The experience we gained in Chile, Bolivia, Peru, India, and Uganda taught us that (1) bringing experts from other countries was very stimulating for children as they are naturally curious about other cultures and encourages a collaboration beyond borders; (2) high-school students who were already interested in science were always very eager to interact with real astronomers doing research to ask for career advice; (3) inquiry-based methods are important to make the learning process more effective and we have therefore, re-adapted the activities in our Handbook according to these; (4) local teachers and university students involved in our activities have the potential to carry out follow-up activities, and examples are those from Uganda and India.

Understanding of impurity behavior in SST-1 plasmas using visible spectroscopy

International Nuclear Information System (INIS)

Manchanda, Ranjana; Ramaiya, Nilam; Chowdhuri, Malay Bikas; Banerjee, Santanu; Ghosh, Joydeep

2015-01-01

Studies of impurity behavior in SST-1 plasma have been carried out using visible spectroscopic systems installed on the tokomak. This has been carried out using a low resolution and broadband survey spectrometer covering a 350-900 nm wavelength range, 0.5 m visible spectrometer having 600 and 1200 grooves/mm grating coupled with CCD camera and interference filter and photomultiplier (PMT) tube based systems. Temporal evolution of the hydrogen (H α , H β ) and impurities emissions like, C II, C III, O I, O II, O III, O V and a visible Continuum at 536.0 nm have been monitored using the PMT based system to understand impurity charge state evolution during plasma discharges. All systems are absolutely calibrated for impurity influx and plasma parameter estimations. Observed spectral lines in the visible range have been identified to recognize the presence of various impurities in the SST-1 plasmas. Comparison of impurities emission has been made for different plasma currents and toroidal magnetic fields. An analysis has been carried out to understand the impurities activities in plasmas of SST-1 tokomak in presence and absence of installed plasma facing components (PFC). Significantly higher carbon emissions have been observed indicating higher carbon content in the plasma with graphite PFCs installed. (author)

Impurity-induced moments in underdoped cuprates

International Nuclear Information System (INIS)

Khaliullin, G.; Kilian, R.; Krivenko, S.; Fulde, P.

1997-01-01

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-potential approximation. Further, the Kondo screening of an impurity-induced local spin by charge carriers is discussed. copyright 1997 The American Physical Society

Increasing physical activity with mobile devices: a meta-analysis.

Science.gov (United States)

Fanning, Jason; Mullen, Sean P; McAuley, Edward

2012-11-21

Regular physical activity has established physical and mental health benefits; however, merely one quarter of the U.S. adult population meets national physical activity recommendations. In an effort to engage individuals who do not meet these guidelines, researchers have utilized popular emerging technologies, including mobile devices (ie, personal digital assistants [PDAs], mobile phones). This study is the first to synthesize current research focused on the use of mobile devices for increasing physical activity. To conduct a meta-analysis of research utilizing mobile devices to influence physical activity behavior. The aims of this review were to: (1) examine the efficacy of mobile devices in the physical activity setting, (2) explore and discuss implementation of device features across studies, and (3) make recommendations for future intervention development. We searched electronic databases (PubMed, PsychINFO, SCOPUS) and identified publications through reference lists and requests to experts in the field of mobile health. Studies were included that provided original data and aimed to influence physical activity through dissemination or collection of intervention materials with a mobile device. Data were extracted to calculate effect sizes for individual studies, as were study descriptives. A random effects meta-analysis was conducted using the Comprehensive Meta-Analysis software suite. Study quality was assessed using the quality of execution portion of the Guide to Community Preventative Services data extraction form. Four studies were of "good" quality and seven of "fair" quality. In total, 1351 individuals participated in 11 unique studies from which 18 effects were extracted and synthesized, yielding an overall weight mean effect size of g = 0.54 (95% CI = 0.17 to 0.91, P = .01). Research utilizing mobile devices is gaining in popularity, and this study suggests that this platform is an effective means for influencing physical activity behavior. Our focus

Biological and chemical interactions excelerating the removal of impurities from fly ashes

Directory of Open Access Journals (Sweden)

Štyriaková Iveta

2002-03-01

Full Text Available The mesophilic bacteria were isolated from the deposit of fly ash in Chalmová (Slovakia and identified using the BBL identification system. Bacillus cereus was the dominant species in this deposit of aluminosilicate minerals. Under laboratory conditions , Bacillus cereus accelerated the extraction of major and trace impurities in fly ash during bioleaching processes. This process was dependent on bacterial adhesion and production of organic acids. The effect of organic acids produced by bacteria was detected especially in sites where impregnated metals were found in the aluminosilicate structure. Amorphous spherical aluminosilicate particles in allotriomorphic aluminosilicate grains represent a main mineral component of fly-ash in which also elements such as Fe, Ti, Mn, As are bound. The rate of mobilization of Al, Si and Ti from coal fly ash under biochemically relevant conditions in vitro was previously shown to depend on the quantity of the ash microspheres. The qualitative EDS analyse of leachates confirmed the extraction of toxic elements (As and Mn from the initial sample of fly ash.Heterotrophic bacteria of Bacillus genus are capable to remove impurities from deposited fly-ash. A long-term deposition of energy fly-ash causes chemical and mineralogical changes as a result of weathering processes. Depending on the composition of coal concentrate containing SiO2, Al2O3, Fe2O3, CaO, MgO and other oxides, fly ash can provide a useful preliminary batch for the preparation of glass-ceramics or zeolite after extracting of bacterially dissolved elements from it. The mobility of major impurities (Ca and Fe and heavy metals, caused by biochemical leaching of fly ash, suggests the possibility of the development of an alternative way of this raw material treatment. The advantage of bioleaching is relatively low cost and the subsequent low demand for energy compared with conventional technologies.

Impurities in uranium process solutions

International Nuclear Information System (INIS)

Boydell, D.W.

1980-01-01

Several uranium purification circuits are presented in tabular form together with the average major impurity levels associated with each. The more common unit operations in these circuits, namely strong- and weak-base ion-exchange, solvent extraction and the precipitation of impurities are then discussed individually. Particular attention is paid to the effect and removal of impurities in each of these four unit operations. (author)

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

Science.gov (United States)

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 pH5 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.

Activation analysis with small mobile reactors

International Nuclear Information System (INIS)

Chung, C.

1990-01-01

A small nuclear reactor (a low-power reactor without heat removal devices) usually has thermal power output under 100 W and an average in-core thermal neutron flux below 10 9 n/cm 2 s. Conventional activation analysis is restricted to determination of specific elements with large neutron capture cross sections in sizable samples. In-vivo prompt gamma activation analysis (IVPGAA) can be used for diagnosis of elemental composition of the human body, particularly the essential elements Ca, Cl, N, and P in the whole body, and toxic Cd and Hg in contaminated organs. In this chapter, activation analysis using an external neutron beam from the Tsing Hua Mobile Educational Reactor (THMER) for in vivo activation is described. Characteristics of the mobile reactor, in-vivo medical diagnosis, and radiation safety are emphasized. 17 refs, 12 figs, 3 tabs

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

Science.gov (United States)

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.

Neo-classical impurity transport

International Nuclear Information System (INIS)

Stringer, T.E.

The neo-classical theory for impurity transport in a toroidal plasma is outlined, and the results discussed. A general account is given of the impurity behaviour and its dependence on collisionality. The underlying physics is described with special attention to the role of the poloidal rotation

Measuring and controlling method for organic impurities

International Nuclear Information System (INIS)

Aizawa, Motohiro; Igarashi, Hiroo

1995-01-01

The present invention concerns measurement and control for organic impurities contained in ultrapurified water for use in a nuclear power plant. A specimen containing organic impurities leached out of anionic exchange resins and cationic exchange resins is introduced to an organic material decomposing section to decompose organic impurities into organic carbon and other decomposed products. Sulfate ions, nitrate ions, nitrite ions and carbon dioxide are produced by the decomposition of the organic impurities. As a next step, carbon dioxide in the decomposed products is separated by deaerating with a nitrogen gas or an argon gas and then a TOC concentration is measured by a non-dispersion-type infrared spectrometer. Further, a specimen from which carbon dioxide was separated is introduced to a column filled with ion exchange resins and, after concentrating inorganic ion impurities, the inorganic ion impurities are identified by using a measuring theory of an ion chromatographic method of eluting and separating inorganic ion impurities and detecting them based on the change of electroconductivity depending on the kinds of the inorganic ion impurities. Organic impurities can be measured and controlled, to improve the reliability of water quality control. (N.H.)

Dynamical impurity problems

International Nuclear Information System (INIS)

Emery, V.J.; Kivelson, S.A.

1993-01-01

In the past few years there has been a resurgence of interest in dynamical impurity problems, as a result of developments in the theory of correlated electron systems. The general dynamical impurity problem is a set of conduction electrons interacting with an impurity which has internal degrees of freedom. The simplest and earliest example, the Kondo problem, has attracted interest since the mid-sixties not only because of its physical importance but also as an example of a model displaying logarithmic divergences order by order in perturbation theory. It provided one of the earliest applications of the renormalization group method, which is designed to deal with just such a situation. As we shall see, the antiferromagnetic Kondo model is controlled by a strong-coupling fixed point, and the essence of the renormalization group solution is to carry out the global renormalization numerically starting from the original (weak-coupling) Hamiltonian. In these lectures, we shall describe an alternative route in which we identify an exactly solvable model which renormalizes to the same fixed point as the original dynamical impurity problem. This approach is akin to determining the critical behavior at a second order phase transition point by solving any model in a given universality class

Dynamical impurity problems

Energy Technology Data Exchange (ETDEWEB)

Emery, V.J. [Brookhaven National Lab., Upton, NY (United States); Kivelson, S.A. [California Univ., Los Angeles, CA (United States). Dept. of Physics

1993-12-31

In the past few years there has been a resurgence of interest in dynamical impurity problems, as a result of developments in the theory of correlated electron systems. The general dynamical impurity problem is a set of conduction electrons interacting with an impurity which has internal degrees of freedom. The simplest and earliest example, the Kondo problem, has attracted interest since the mid-sixties not only because of its physical importance but also as an example of a model displaying logarithmic divergences order by order in perturbation theory. It provided one of the earliest applications of the renormalization group method, which is designed to deal with just such a situation. As we shall see, the antiferromagnetic Kondo model is controlled by a strong-coupling fixed point, and the essence of the renormalization group solution is to carry out the global renormalization numerically starting from the original (weak-coupling) Hamiltonian. In these lectures, we shall describe an alternative route in which we identify an exactly solvable model which renormalizes to the same fixed point as the original dynamical impurity problem. This approach is akin to determining the critical behavior at a second order phase transition point by solving any model in a given universality class.

Determination of trace impurities in iron-based alloy using neutron activation analysis

International Nuclear Information System (INIS)

Zaidi, J.H.; Waheed, S.; Ahmad, S.

2000-01-01

A radiochemical neutron activation analysis procedure has been developed and applied to investigate 40 major, minor, and trace impurities in iron-based alloy. A comparison of RNAA and INAA indicated a significant improvement in the detection limits. The extensive use of these alloys in the heavy mechanical industry, manufacturing of aircraft engines, nuclear applications, medical devices and chemical equipment requires their precise characterization. The concentration of iron in the iron-based alloy was found to be 86.7%, whereas Ca, Cr, K, Mg, Mn, V and W were the other constituents of the alloy, which constituted to around 12.89%. The rest of the elements were present in minor or trace levels. Most of the rare earth elements were also present in trace amounts. (orig.)

Identification and characterization of potential impurities of donepezil.

Science.gov (United States)

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.

Development and Validation of a Precise, Single HPLC Method for the Determination of Tolperisone Impurities in API and Pharmaceutical Dosage Forms.

Science.gov (United States)

Raju, Thummala Veera Raghava; Seshadri, Raja Kumar; Arutla, Srinivas; Mohan, Tharlapu Satya Sankarsana Jagan; Rao, Ivaturi Mrutyunjaya; Nittala, Someswara Rao

2013-01-01

A novel, sensitive, stability-indicating HPLC method has been developed for the quantitative estimation of Tolperisone-related impurities in both bulk drugs and pharmaceutical dosage forms. Effective chromatographic separation was achieved on a C18 stationary phase with a simple mobile phase combination delivered in a simple gradient programme, and quantitation was by ultraviolet detection at 254 nm. The mobile phase consisted of a buffer and acetonitrile delivered at a flow rate 1.0 ml/min. The buffer consisted of 0.01 M potassium dihydrogen phosphate with the pH adjusted to 8.0 by using diethylamine. In the developed HPLC method, the resolution between Tolperisone and its four potential impurities was found to be greater than 2.0. Regression analysis showed an R value (correlation coefficient) of greater than 0.999 for the Tolperisone impurities. This method was capable of detecting all four impurities of Tolperisone at a level of 0.19 μg/mL with respect to the test concentration of 1000 μg/mL for a 10 µl injection volume. The tablets were subjected to the stress conditions of hydrolysis, oxidation, photolysis, and thermal degradation. Considerable degradation was found to occur in base hydrolysis, water hydrolysis, and oxidation. The stress samples were assayed against a qualified reference standard and the mass balance was found to be close to 100%. The established method was validated and found to be linear, accurate, precise, specific, robust, and rugged.

A validated stability-indicating UPLC method for desloratadine and its impurities in pharmaceutical dosage forms.

Science.gov (United States)

Rao, Dantu Durga; Satyanarayana, N V; Malleswara Reddy, A; Sait, Shakil S; Chakole, Dinesh; Mukkanti, K

2010-02-05

A novel stability-indicating gradient reverse phase ultra-performance liquid chromatographic (RP-UPLC) method was developed for the determination of purity of desloratadine in presence of its impurities and forced degradation products. The method was developed using Waters Aquity BEH C18 column with mobile phase containing a gradient mixture of solvents A and B. The eluted compounds were monitored at 280nm. The run time was 8min within which desloratadine and its five impurities were well separated. Desloratadine was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal and photolytic degradation. Desloratadine was found to degrade significantly in oxidative and thermal stress conditions and stable in acid, base, hydrolytic and photolytic degradation conditions. The degradation products were well resolved from main peak and its impurities, thus proved the stability-indicating power of the method. The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision and robustness. This method was also suitable for the assay determination of desloratadine in pharmaceutical dosage forms.

A Learning Activity Design Framework for Supporting Mobile Learning

Directory of Open Access Journals (Sweden)

Jalal Nouri

2016-01-01

Full Text Available This article introduces the Learning Activity Design (LEAD framework for the development and implementation of mobile learning activities in primary schools. The LEAD framework draws on methodological perspectives suggested by design-based research and interaction design in the specific field of technology-enhanced learning (TEL. The LEAD framework is grounded in four design projects conducted over a period of six years. It contributes a new understanding of the intricacies and multifaceted aspects of the design-process characterizing the development and implementation of mobile devices (i.e. smart phones and tablets in curricular activities conducted in Swedish primary schools. This framework is intended to provide both designers and researchers with methodological tools that take account of the pedagogical foundations of technologically-based educational interventions, usability issues related to the interaction with the mobile application developed, multiple data streams generated during the design project, multiple stakeholders involved in the design process and sustainability aspects of the mobile learning activities implemented in the school classroom.

Impurity Induced Phase Competition and Supersolidity

Science.gov (United States)

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.

Effects of alloying and transmutation impurities on stability and mobility of helium in tungsten under a fusion environment

International Nuclear Information System (INIS)

Wu Xuebang; Kong Xiangshan; You Yuwei; Liu, C.S.; Fang, Q.F.; Chen Junling; Luo, G.-N.; Wang Zhiguang

2013-01-01

The behaviour of helium in metals is particularly significant in fusion research due to the He-induced degradation of materials. A small amount of impurities introduced either by intentional alloying or by transmutation reactions, will interact with He and lead the microstructure and mechanical properties of materials to change. In this paper, we present the results of first-principles calculations on the interactions of He with impurities and He diffusion around them in tungsten (W), including the interstitials Be, C, N, O, and substitutional solutes Re, Ta, Tc, Nb, V, Os, Ti, Si, Zr, Y and Sc. We find that the trapping radii of interstitial atoms on He are much larger than those of substitutional solutes. The binding energies between the substitutional impurities and He increase linearly with the relative charge densities at the He occupation site, indicating that He atoms easily aggregate at the low charge density site. The sequence of diffusion energy barriers of He around the possible alloying elements is Ti > V > Os > Ta > Re. The present results suggest that Ta might be chosen as a relatively suitable alloying element compared with other possible ones. (paper)

The impurity transport in HT-6M tokamak

International Nuclear Information System (INIS)

Xu Wei; Wan Baonian; Xie Jikang

2003-01-01

The space-time profile of impurities has been measured with a multichannel visible spectroscopic detect system and UV rotation-mirror system in the HT-6M tokamak. An ideal impurity transport code has been used to simulate impurities (carbon and oxygen) behaviour during the OHM discharge. The profiles of impurities diffusion and convection coefficient, impurities ion densities in different ionized state, loss power density and effective charge number have been derived. The impurity behaviour during low-hybrid current drive has also been analyzed, the results show that the confinement of particles, impurities and energy has been improved, and emission power and effective charge number have been reduced

Fast neutron-induced changes in net impurity concentration of high-resistivity silicon

International Nuclear Information System (INIS)

Tsveybak, I.; Bugg, W.; Harvey, J.A.; Walter, J.

1992-01-01

Resistivity changes produced by 1 MeV neutron irradiation at room temperature have been measured in float-zone grown n and p-type silicon with initial resistivities ranging from 1.8 to 100 kΩcm. Observed changes are discussed in terms of net electrically active impurity concentration. A model is presented which postulates escape of Si self-interstitials and vacancies from damage clusters and their subsequent interaction with impurities and other pre-existing defects in the lattice. These interactions lead to transfer of B and P from electrically active substitutional configurations into electrically inactive positions (B i , Pi i , and E-center), resulting in changes of net electrically active impurity concentration. The changes in spatial distribution of resistivity are discussed, and the experimental data are fit by theoretical curves. Differences in the behavior of n-type and p-type material are explained on the basis of a faster removal of substitutional P and a more nonuniform spatial distribution of the original P concentration

On impurities transport in a tokamak

International Nuclear Information System (INIS)

Rozhanskij, V.A.

1980-01-01

Transport of impurity ions is analitically analized in the case when main plasma is in plateau or banana regimes but impurity ions - in the Pfirsch-Schlutter mode. It is shown that in the large region of parameters the impUrity transport represents a drift in a p oloidal electric field, averaged from magnetic surface with provision for disturbance of concentration on it. Therefore, transport velocity does not depend on Z value and impurity type, as well as collision frequency both in the plateau and banana regimes. A value of flows is determined by the value of poloidal rotation velocity. At the rotation velocity corresponding to the electric field directed from the centre to periphery impurities are thrown out of a discharge, in the reverse case the flow is directed inside. Refusal from the assumption that Zsub(eff) > approximately 2, does not considerably change the results of work. The approach developed in the process of work can be applied to the case when impurity ions are in the plateau or banana modes

Mechanisms of impurity diffusion in rutile

International Nuclear Information System (INIS)

Peterson, N.L.; Sasaki, J.

1984-01-01

Tracer diffusion of 46 Sc, 51 Cr, 54 Mn, 59 Fe, 60 Co, 63 Ni, and 95 Zr, was measured as functions of crystal orientation, temperature, and oxygen partial pressure in rutile single crystals using the radioactive tracer sectioning technique. Compared to cation self-diffusion, divalent impurities (e.g., Co and Ni) diffuse extremely rapidly in TiO 2 and exhibit a large anisotropy in the diffusion behavior; divalent-impurity diffusion parallel to the c-axis is much larger than it is perpendicular to the c-axis. The diffusion of trivalent impurity ions (Sc and Cr) and tetravalent impurity ions (Zr) is similar to cation self-diffusion, as a function of temperature and of oxygen partial pressure. The divalent impurity ions Co and Ni apparently diffuse as interstitial ions along open channels parallel to the c-axis. The results suggest that Sc, Cr, and Zr ions diffuse by an interstitialcy mechanism involving the simultaneous and cooperative migration of tetravalent interstitial titanium ions and the tracer-impurity ions. Iron ions diffused both as divalent and as trivalent ions. 8 figures

Impurity production and transport at limiters

International Nuclear Information System (INIS)

Matthews, G.F.

1989-01-01

This paper concentrates on the description and evaluation of experiments on the DITE tokamak. These are designed to characterise the processes involved in the production and transport of neutral and ionised impurities near carbon limiters. The need for good diagnostics in the scrape-off layer is highlighted. Langmuir probes are used to provide input data for models of impurity production at limiters. Observations of the radial profiles of carbon and oxygen impurities are compared with the code predictions. Changeover experiments involving hydrogen and helium plasmas are used as a means for investigating the role of the atomic physics and chemistry. The impurity control limiter (ICL) experiment is described which shows how geometry plays an important role in determining the spatial distributions of the neutral and ionised carbon. New diagnostics are required to study the flux and charge state distribution of impurities in the boundary. Preliminary results from an in-situ plasma ion mass-spectrometer are presented. The role of oxygen and the importance of evaluating the wall sources of impurity are emphasised. (orig.)

Study of impurity-defect interaction by perturbed angular correlations: 111Cd in silver

International Nuclear Information System (INIS)

Sage, Francoise.

1975-01-01

The quadrupole interaction of 111 Cd nuclei following the decay of 111 In implanted by the 109 Ag(α,2n) 111 In reaction into a cubic Ag lattice was measured using the time-differential perturbed-angular correlation technique. A non vanishing quadrupole interaction corresponding to a distribution of electric field gradients was observed, due to the interaction between the 111 Cd impurity and the defects created during the recoil of 111 In nuclei. For low temperature (77 K) irradiations, it has been shown that i) the angular correlation pattern depends on the intensity of α beam current, due to the interaction between defect cascades at high α beam intensity; and ii) it also depends on the annealing of the irradiated sample at different temperatures; the change in the defect configuration around the impurities is then due to the mobility of the various defects [fr

Investigations of impurity control in JET using fuelling, and interpretation of experiments using the LIM impurity code

International Nuclear Information System (INIS)

Gondhalekar, A.; Stangeby, P.C.; Elder, J.D.

1994-01-01

Inhibition of contamination of the plasma core in JET by edge impurities during high power heating of deuterium plasmas in limiter configuration using fuelling is demonstrated. By injecting deuterium gas during heating, in the presence of a much larger recycling deuterium flux, a reduction of more than a factor of 2 was effected in n z (0)/Φ z , the ratio of central impurity density to impurity influx at the plasma edge. The reduction in n z (0) was obtained without much effect on peak electron temperature and density. Reduction of plasma contamination by gas fuelling was observed also when hot spots formed on the limiter, a condition that without simultaneous gas fuelling culminated in runaway plasma contamination. Detailed analysis of the experiments is undertaken with the purpose of identifying the processes by which plasma contamination was inhibited, employing standard limiter plasma contamination modelling. Processes which might produce the observed impurity inhibiting effects of gas injection include: (a) reduction in impurity production at the limiter; (b) increase in impurity screening in the scrape-off layer; (c) increase in radial impurity transport at the plasma edge; (d) increase in average deuteron flow velocity to the limiter along the scrape-off layer. These are examined in detail using the Monte Carlo limiter impurity transport code LIM. Bearing in mind that uncertainties exist both in the choice of appropriate modelling assumptions to be used and in the measurement of required edge plasma parameters, changes in n z (0)/Φ z by a factor of 2 are at the limit of the present modelling capability. However, comparison between LIM code simulations and measurements of plasma impurity content indicate that the standard limiter plasma contamination model may not be adequate and that other processes need to be added in order to be able to describe the experiments in JET. (author). 24 refs, 2 figs, 8 tabs

Void growth suppression by dislocation impurity atmospheres

International Nuclear Information System (INIS)

Weertman, J.; Green, W.V.

1976-01-01

A detailed calculation is given of the effect of an impurity atmosphere on void growth under irradiation damage conditions. Norris has proposed that such an atmosphere can suppress void growth. The hydrostatic stress field of a dislocation that is surrounded by an impurity atmosphere was found and used to calculate the change in the effective radius of a dislocation line as a sink for interstitials and vacancies. The calculation of the impurity concentration in a Cottrell cloud takes into account the change in hydrostatic pressure produced by the presence of the cloud itself. It is found that void growth is eliminated whenever dislocations are surrounded by a condensed atmosphere of either oversized substitutional impurity atoms or interstitial impurity atoms. A condensed atmosphere will form whenever the average impurity concentration is larger than a critical concentration

Determination of the impurity content of B, Cd, Cu, W in uranium-gadolinium pellets

International Nuclear Information System (INIS)

Chen Lan; Zhang Jiansheng; Zhang Bo; Shao Yan

2010-01-01

This paper deals with determining the impurity content of B, Cd, Cu and W in Uranium-gadolinium Pellets. Set up the method: dissolve the sample in nitric acid and mannitol; use the 3 mol/L HNO 3 solution for mobile phase, CL-TBP resin for stationary phase to separate the Uranium from its nitric acid solution, collect the leaching solution , analysed by the Multi-component spectra fitting ICP-AES. The studies also includes the setting up and validity testing of the MSF model. The studies conducted suggests that:the sampling mass 0.2000 g, prepared sample volume is 6 mL; range of the determination concentration Cu, W(3-300) μg/g; B, Cd (0.3-30) μg/g .The recovery of the impurities is (89-120)%, relative standard deviation is better than 8%. (authors)

Fundamental limits on the electron mobility of β-Ga2O3.

Science.gov (United States)

Kang, Youngho; Krishnaswamy, Karthik; Peelaers, Hartwin; Van de Walle, Chris G

2017-06-14

We perform first-principles calculations to investigate the electronic and vibrational spectra and the electron mobility of β-Ga 2 O 3 . We calculate the electron-phonon scattering rate of the polar optical phonon modes using the Vogl model in conjunction with Fermi's golden rule; this enables us to fully take the anisotropic phonon spectra of the monoclinic lattice of β-Ga 2 O 3 into account. We also examine the scattering rate due to ionized impurities or defects using a Yukawa-potential-based model. We consider scattering due to donor impurities, as well as the possibility of compensation by acceptors such as Ga vacancies. We then calculate the room-temperature mobility of β-Ga 2 O 3 using the Boltzmann transport equation within the relaxation time approximation, for carrier densities in the range from 10 17 to 10 20 cm -3 . We find that the electron-phonon interaction dominates the mobility for carrier densities of up to 10 19 cm -3 . We also find that the intrinsic anisotropy in the mobility is small; experimental findings of large anisotropy must therefore be attributed to other factors. We attribute the experimentally observed reduction of the mobility with increasing carrier density to increasing levels of compensation, which significantly affect the mobility.

Fundamental limits on the electron mobility of β-Ga2O3

Science.gov (United States)

Kang, Youngho; Krishnaswamy, Karthik; Peelaers, Hartwin; Van de Walle, Chris G.

2017-06-01

We perform first-principles calculations to investigate the electronic and vibrational spectra and the electron mobility of β-Ga2O3. We calculate the electron-phonon scattering rate of the polar optical phonon modes using the Vogl model in conjunction with Fermi’s golden rule; this enables us to fully take the anisotropic phonon spectra of the monoclinic lattice of β-Ga2O3 into account. We also examine the scattering rate due to ionized impurities or defects using a Yukawa-potential-based model. We consider scattering due to donor impurities, as well as the possibility of compensation by acceptors such as Ga vacancies. We then calculate the room-temperature mobility of β-Ga2O3 using the Boltzmann transport equation within the relaxation time approximation, for carrier densities in the range from 1017 to 1020 cm-3. We find that the electron-phonon interaction dominates the mobility for carrier densities of up to 1019 cm-3. We also find that the intrinsic anisotropy in the mobility is small; experimental findings of large anisotropy must therefore be attributed to other factors. We attribute the experimentally observed reduction of the mobility with increasing carrier density to increasing levels of compensation, which significantly affect the mobility.

Electron mobility in few-layer MoxW1-xS2

International Nuclear Information System (INIS)

Chandrasekar, Hareesh; Nath, Digbijoy N

2015-01-01

Heterostructures of two-dimensional (2D) layered materials are increasingly being explored for electronics in order to potentially extend conventional transistor scaling and to exploit new device designs and architectures. Alloys form a key underpinning of any heterostructure device technology and therefore an understanding of their electronic properties is essential. In this paper, we study the intrinsic electron mobility in few-layer Mo x W 1−x S 2 as limited by various scattering mechanisms. The room temperature, energy-dependent scattering times corresponding to polar longitudinal optical (LO) phonon, alloy and background impurity scattering mechanisms are estimated based on the Born approximation to Fermi’s golden rule. The contribution of individual scattering rates is analyzed as a function of 2D electron density as well as of alloy composition in Mo x W 1−x S 2 . While impurity scattering limits the mobility for low carrier densities (<2–4×10 12 cm −2 ), LO polar phonon scattering is the dominant mechanism for high electron densities. Alloy scattering is found to play a non-negligible role for 0.5 < x < 0.7 in Mo x W 1−x S 2 . The LO phonon-limited and impurity-limited mobilities show opposing trends with respect to alloy mole fractions. The understanding of electron mobility in Mo x W 1−x S 2 presented here is expected to enable the design and realization of heterostructures and devices based on alloys of MoS 2 and WS 2 . (paper)

Kinetic neoclassical calculations of impurity radiation profiles

Directory of Open Access Journals (Sweden)

D.P. Stotler

2017-08-01

Full Text Available Modifications of the drift-kinetic transport code XGC0 to include the transport, ionization, and recombination of individual charge states, as well as the associated radiation, are described. The code is first applied to a simulation of an NSTX H-mode discharge with carbon impurity to demonstrate the approach to coronal equilibrium. The effects of neoclassical phenomena on the radiated power profile are examined sequentially through the activation of individual physics modules in the code. Orbit squeezing and the neoclassical inward pinch result in increased radiation for temperatures above a few hundred eV and changes to the ratios of charge state emissions at a given electron temperature. Analogous simulations with a neon impurity yield qualitatively similar results.

Supporting Activity-Based Computingusing Dynamically (De)Composable Mobile Applications

DEFF Research Database (Denmark)

Schultz, Ulrik Pagh; Schougaard, Kari Rye

2004-01-01

the document-centered paradigm for pervasive computing: it crosscuts work with different kinds of entities and sets the focus on the user and the user's tasks. In domain such as healthcare, activities are fundamentally mobile: doctors and nurses move throughout the hospital as their work progresses. Hence......, the computer must support mobility of activities. For this reason, we consider it important to investigate whether a computing platform that embraces mobility at a fundamental level supports implementing software for this new paradigm. This paper describes our initial design ideas for supporting activity......-centered computing in the Pervasive Object Model Project (POMP), a project which concerns the development of a platform for pervasive computing applications. We first describe POMP, the present the notion of activity-based computing, and last investigate how activity-based computing can be implemented in POMP....

MOBILE CAMPUS: A REFLECTIVE AND COLLECTIVE DIMENSION OF EDUCATIONAL ACTIVITIES MEDIATED BY MOBILE TECHNOLOGY

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Ivan Yu. Travkin

2013-01-01

Full Text Available The author considers a definition and general characteristics of the mobile campus allowing to ensure a combination of informal and social types of the educational activities with formal learning in a traditional educational institution (institutes of higher education. A fundamental element of the mobile campus is intelligent algorithms providing learning analyst for personalized learning experience. Also the article examines connections between the mobile campus and a learning community, a personal learning network and electronic student profile.

High electron mobility in Ga(In)NAs films grown by molecular beam epitaxy

International Nuclear Information System (INIS)

Miyashita, Naoya; Ahsan, Nazmul; Monirul Islam, Muhammad; Okada, Yoshitaka; Inagaki, Makoto; Yamaguchi, Masafumi

2012-01-01

We report the highest mobility values above 2000 cm 2 /Vs in Si doped GaNAs film grown by molecular beam epitaxy. To understand the feature of the origin which limits the electron mobility in GaNAs, temperature dependences of mobility were measured for high mobility GaNAs and referential low mobility GaInNAs. Temperature dependent mobility for high mobility GaNAs is similar to the GaAs case, while that for low mobility GaInNAs shows large decrease in lower temperature region. The electron mobility of high quality GaNAs can be explained by intrinsic limiting factor of random alloy scattering and extrinsic factor of ionized impurity scattering.

Low-Z impurities in PLT

International Nuclear Information System (INIS)

Hinnov, E.; Suckewer, S.; Bol, K.; Hawryluk, R.; Hosea, J.; Meservey, E.

1977-11-01

Low-Z impurities concentrations (oxygen and carbon) have been measured in different discharges in PLT. The contribution to Z/sub eff/, influx rates and radiation losses by oxygen and carbon were obtained. An inverse correlation was found between the low-Z impurity density (and also the edge ion temperature) and the high-Z impurity (tungsten) density. A one-dimensional computer transport model has been used to calculate the spatial profiles of different oxygen and carbon ionization states. This model predicts that fully stripped oxygen and carbon ions should exist near the plasma periphery

Labor Mobility and Patenting Activity

DEFF Research Database (Denmark)

Kaiser, Ulrich; Kongsted, Hans Christian; Rønde, Thomas

We measure the quantitative importance of labor mobility as a vehicle for the transmission of knowledge and skills across firms. For this purpose we create a unique data set that matches all applications of Danish firms at the European Patent Office to linked employer-employee register data...... for the years 1999-2002. The Danish workforce is split into "R&D workers", who hold a bachelor's or a master's degree in a technical field, and "non{R&D workers". We find that mobile R&D workers ("R&D joiners"') contribute more to patenting activity than immobile R&D workers. Furthermore, R&D workers who have...... previously been employed by a patenting firm ("patent exposed workers") have a larger effect on patenting activity than R&D workers without this experience. Patent exposed R&D joiners constitute the most productive group of workers: for firms that patented prior to 1999, one additional worker of this type...

Impurity Correction Techniques Applied to Existing Doping Measurements of Impurities in Zinc

Science.gov (United States)

Pearce, J. V.; Sun, J. P.; Zhang, J. T.; Deng, X. L.

2017-01-01

Impurities represent the most significant source of uncertainty in most metal fixed points used for the realization of the International Temperature Scale of 1990 (ITS-90). There are a number of different methods for quantifying the effect of impurities on the freezing temperature of ITS-90 fixed points, many of which rely on an accurate knowledge of the liquidus slope in the limit of low concentration. A key method of determining the liquidus slope is to measure the freezing temperature of a fixed-point material as it is progressively doped with a known amount of impurity. Recently, a series of measurements of the freezing and melting temperature of `slim' Zn fixed-point cells doped with Ag, Fe, Ni, and Pb were presented. Here, additional measurements of the Zn-X system are presented using Ga as a dopant, and the data (Zn-Ag, Zn-Fe, Zn-Ni, Zn-Pb, and Zn-Ga) have been re-analyzed to demonstrate the use of a fitting method based on Scheil solidification which is applied to both melting and freezing curves. In addition, the utility of the Sum of Individual Estimates method is explored with these systems in the context of a recently enhanced database of liquidus slopes of impurities in Zn in the limit of low concentration.

A MULTIDISCIPLINARY ANALYTICAL FRAMEWORK FOR STUDYING ACTIVE MOBILITY PATTERNS

Directory of Open Access Journals (Sweden)

D. Orellana

2016-06-01

Full Text Available Intermediate cities are urged to change and adapt their mobility systems from a high energy-demanding motorized model to a sustainable low-motorized model. In order to accomplish such a model, city administrations need to better understand active mobility patterns and their links to socio-demographic and cultural aspects of the population. During the last decade, researchers have demonstrated the potential of geo-location technologies and mobile devices to gather massive amounts of data for mobility studies. However, the analysis and interpretation of this data has been carried out by specialized research groups with relatively narrow approaches from different disciplines. Consequently, broader questions remain less explored, mainly those relating to spatial behaviour of individuals and populations with their geographic environment and the motivations and perceptions shaping such behaviour. Understanding sustainable mobility and exploring new research paths require an interdisciplinary approach given the complex nature of mobility systems and their social, economic and environmental impacts. Here, we introduce the elements for a multidisciplinary analytical framework for studying active mobility patterns comprised of three components: a Methodological, b Behavioural, and c Perceptual. We demonstrate the applicability of the framework by analysing mobility patterns of cyclists and pedestrians in an intermediate city integrating a range of techniques, including: GPS tracking, spatial analysis, auto-ethnography, and perceptual mapping. The results demonstrated the existence of non-evident spatial behaviours and how perceptual features affect mobility. This knowledge is useful for developing policies and practices for sustainable mobility planning.

a Multidisciplinary Analytical Framework for Studying Active Mobility Patterns

Science.gov (United States)

Orellana, D.; Hermida, C.; Osorio, P.

2016-06-01

Intermediate cities are urged to change and adapt their mobility systems from a high energy-demanding motorized model to a sustainable low-motorized model. In order to accomplish such a model, city administrations need to better understand active mobility patterns and their links to socio-demographic and cultural aspects of the population. During the last decade, researchers have demonstrated the potential of geo-location technologies and mobile devices to gather massive amounts of data for mobility studies. However, the analysis and interpretation of this data has been carried out by specialized research groups with relatively narrow approaches from different disciplines. Consequently, broader questions remain less explored, mainly those relating to spatial behaviour of individuals and populations with their geographic environment and the motivations and perceptions shaping such behaviour. Understanding sustainable mobility and exploring new research paths require an interdisciplinary approach given the complex nature of mobility systems and their social, economic and environmental impacts. Here, we introduce the elements for a multidisciplinary analytical framework for studying active mobility patterns comprised of three components: a) Methodological, b) Behavioural, and c) Perceptual. We demonstrate the applicability of the framework by analysing mobility patterns of cyclists and pedestrians in an intermediate city integrating a range of techniques, including: GPS tracking, spatial analysis, auto-ethnography, and perceptual mapping. The results demonstrated the existence of non-evident spatial behaviours and how perceptual features affect mobility. This knowledge is useful for developing policies and practices for sustainable mobility planning.

Defect engineering: reduction effect of hydrogen atom impurities in HfO2-based resistive-switching memory devices

International Nuclear Information System (INIS)

Kim, Seonghyun; Park, Jubong; Jung, Seungjae; Lee, Wootae; Shin, Jungho; Hwang, Hyunsang; Lee, Daeseok; Woo, Jiyong; Choi, Godeuni

2012-01-01

In this study, we propose a new and effective methodology for improving the resistive-switching performance of memory devices by high-pressure hydrogen annealing under ambient conditions. The reduction effect results in the uniform creation of oxygen vacancies that in turn enable forming-free operation and afford uniform switching characteristics. In addition, H + and mobile hydroxyl (OH − ) ions are generated, and these induce fast switching operation due to the higher mobility compared to oxygen ions. Defect engineering, specifically, the introduction of hydrogen atom impurities, improves the device performance for metal–oxide-based resistive-switching random access memory devices. (paper)

Development and Validation of a Precise, Single HPLC Method for the Determination of Tolperisone Impurities in API and Pharmaceutical Dosage Forms

OpenAIRE

Raju, Thummala Veera Raghava; Seshadri, Raja Kumar; Arutla, Srinivas; Mohan, Tharlapu Satya Sankarsana Jagan; Rao, Ivaturi Mrutyunjaya; Nittala, Someswara Rao

2012-01-01

A novel, sensitive, stability-indicating HPLC method has been developed for the quantitative estimation of Tolperisone-related impurities in both bulk drugs and pharmaceutical dosage forms. Effective chromatographic separation was achieved on a C18 stationary phase with a simple mobile phase combination delivered in a simple gradient programme, and quantitation was by ultraviolet detection at 254 nm. The mobile phase consisted of a buffer and acetonitrile delivered at a flow rate 1.0 ml/min. ...

Impurity energy level in the Haldane gap

International Nuclear Information System (INIS)

Wang Wei; Lu Yu

1995-11-01

An impurity bond J' in a periodic 1D antiferromagnetic spin 1 chain with exchange J is considered. Using the numerical density matrix renormalization group method, we find an impurity energy level in the Haldane gap, corresponding to a bound state near the impurity bond. When J' J. The impurity level appears only when the deviation dev = (J'- J)/J' is greater than B c , which is close to 0.3 in our calculation. (author). 15 refs, 4 figs

Identification, characterization and quantification of new impurities by LC-ESI/MS/MS and LC-UV methods in rivastigmine tartrate active pharmaceutical ingredient.

Science.gov (United States)

Thomas, Saji; Shandilya, Sanjeev; Bharati, Amber; Paul, Saroj Kumar; Agarwal, Ashutosh; Mathela, Chandra S

2012-01-05

Six impurities were detected at trace level in rivastigmine tartrate drug substance by a newly developed high performance liquid chromatography method. Three impurities were characterized rapidly and three impurities were found to be unknown. The unknown impurities were enriched and identified with a combination of semi-preparative HPLC and LC/MS/MS techniques. Proposed structures were further confirmed by characterization using NMR, FT-IR, and EA techniques of impurity standards. Based on the spectroscopic, spectrometric and elemental analysis data unknown impurities were characterized as 3-[1-(dimethylamino)ethyl]phenyl N-ethyl-N-methyl carbamate N-oxide, ethyl-methyl-carbamic acid 4-(1-dimethylamino-ethyl)-phenyl ester and ethyl-methyl-carbamic acid 2-(1-dimethylamino-ethyl)-phenyl ester. A plausible mechanism for the formation of these impurities is also proposed. The method was validated according to ICH guidelines for fourteen impurities to demonstrate specificity, precision, linearity, accuracy and stability indicating nature of the method. Regression analysis showed correlation coefficient value greater than 0.999 for rivastigmine tartrate and its impurities. Accuracy of the method was established based on the recovery obtained between 93.41 and 113.33% for all impurities. Copyright © 2011 Elsevier B.V. All rights reserved.

Multi-impurity polarons in a dilute Bose-Einstein condensate

International Nuclear Information System (INIS)

Santamore, D H; Timmermans, Eddy

2011-01-01

We describe the ground state of a large, dilute, neutral atom Bose-Einstein condensate (BEC) doped with N strongly coupled mutually indistinguishable, bosonic neutral atoms (referred to as ‘impurity’) in the polaron regime where the BEC density response to the impurity atoms remains significantly smaller than the average density of the surrounding BEC. We find that N impurity atoms with N ≠ 1 can self-localize at a lower value of the impurity-boson interaction strength than a single impurity atom. When the ‘bare’ short-range impurity-impurity repulsion does not play a significant role, the self-localization of multiple bosonic impurity atoms into the same single particle orbital (which we call co-self-localization) is the nucleation process of the phase separation transition. When the short-range impurity-impurity repulsion successfully competes with co-self-localization, the system may form a stable liquid of self-localized single impurity polarons. (paper)

Associations between children’s independent mobility and physical activity

Science.gov (United States)

2014-01-01

Background Independent mobility describes the freedom of children to travel and play in public spaces without adult supervision. The potential benefits for children are significant such as social interactions with peers, spatial and traffic safety skills and increased physical activity. Yet, the health benefits of independent mobility, particularly on physical activity accumulation, are largely unexplored. This study aimed to investigate associations of children’s independent mobility with light, moderate-to-vigorous, and total physical activity accumulation. Methods In 2011 - 2012, 375 Australian children aged 8-13 years (62% girls) were recruited into a cross-sectional study. Children’s independent mobility (i.e. independent travel to school and non-school destinations, independent outdoor play) and socio-demographics were assessed through child and parent surveys. Physical activity intensity was measured objectively through an Actiheart monitor worn on four consecutive days. Associations between independent mobility and physical activity variables were analysed using generalized linear models, accounting for clustered sampling, Actiheart wear time, socio-demographics, and assessing interactions by sex. Results Independent travel (walking, cycling, public transport) to school and non-school destinations were not associated with light, moderate-to-vigorous and total physical activity. However, sub-analyses revealed a positive association between independent walking and cycling (excluding public transport) to school and total physical but only in boys (b = 36.03, p physical activity (b = 29.76, p physical activity. When assessing differences by sex, the observed significant associations of independent outdoor play with light and total physical activity remained in girls but not in boys. All other associations showed no significant differences by sex. Conclusions Independent outdoor play may boost children’s daily physical activity levels

Collision of impurities with Bose–Einstein condensates

Science.gov (United States)

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.

Determination of Impurities of Atrazine by HPLP-MS

Energy Technology Data Exchange (ETDEWEB)

Canping, Pan [Department of Applied Chemistry, China Agricultural University Beijing (China)

2009-07-15

The determination of the main impurities of the herbicide atrazine by GC/FID, GC/MS and LC/MS is described. The most relevant technical impurities were synthesized and characterized by IR and UV spectroscopy as well. The impurity profiles of different technical grade formulated products were tested and the typical impurities identified. (author)

Influence of iron impurities on defected graphene

Energy Technology Data Exchange (ETDEWEB)

Faccio, Ricardo; Pardo, Helena [Centro NanoMat, Cryssmat-Lab, DETEMA, Polo Tecnológico de Pando, Facultad de Química, Universidad de la República, Cno. Saravia s/n, CP 91000 Pando (Uruguay); Centro Interdisciplinario en Nanotecnología, Química y Física de Materiales, Espacio Interdisciplinario, Universidad de la República, Montevideo (Uruguay); Araújo-Moreira, Fernando M. [Materials and Devices Group, Department of Physics, Universidade Federal de São Carlos, SP 13565-905 (Brazil); Mombrú, Alvaro W., E-mail: amombru@fq.edu.uy [Centro NanoMat, Cryssmat-Lab, DETEMA, Polo Tecnológico de Pando, Facultad de Química, Universidad de la República, Cno. Saravia s/n, CP 91000 Pando (Uruguay); Centro Interdisciplinario en Nanotecnología, Química y Física de Materiales, Espacio Interdisciplinario, Universidad de la República, Montevideo (Uruguay)

2015-03-01

Highlights: • The interaction among a multivacancy graphene system and iron impurities is studied. • The studied iron impurities were single atom and tetrahedral and octahedral clusters. • DFT calculations using the VASP code were performed. • The embedding of Fe affects the structure and electronic behavior in the graphene. • Half metal or semimetal behavior can be obtained, depending on the Fe impurities. - Abstract: The aim of this work is to study the interaction of selected iron cluster impurities and a multivacancy graphene system, in terms of the structural distortion that the impurities cause as well as their magnetic response. While originally, the interaction has been limited to vacancies and isolated metallic atoms, in this case, we consider small iron clusters. This study was undertaken using Density Functional Theory (DFT) calculations. The influence of the iron impurities in the electronic structure of the vacant graphene system is discussed. The main conclusion of this work is that the presence of iron impurities acts lowering the magnetic signal due to the occurrence of spin pairing between carbon and iron, instead of enhancing the possible intrinsic carbon magnetism.

Influence of iron impurities on defected graphene

International Nuclear Information System (INIS)

Faccio, Ricardo; Pardo, Helena; Araújo-Moreira, Fernando M.; Mombrú, Alvaro W.

2015-01-01

Highlights: • The interaction among a multivacancy graphene system and iron impurities is studied. • The studied iron impurities were single atom and tetrahedral and octahedral clusters. • DFT calculations using the VASP code were performed. • The embedding of Fe affects the structure and electronic behavior in the graphene. • Half metal or semimetal behavior can be obtained, depending on the Fe impurities. - Abstract: The aim of this work is to study the interaction of selected iron cluster impurities and a multivacancy graphene system, in terms of the structural distortion that the impurities cause as well as their magnetic response. While originally, the interaction has been limited to vacancies and isolated metallic atoms, in this case, we consider small iron clusters. This study was undertaken using Density Functional Theory (DFT) calculations. The influence of the iron impurities in the electronic structure of the vacant graphene system is discussed. The main conclusion of this work is that the presence of iron impurities acts lowering the magnetic signal due to the occurrence of spin pairing between carbon and iron, instead of enhancing the possible intrinsic carbon magnetism

Impurity bubbles in a BEC

Science.gov (United States)

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.

Impurity bound states in mesoscopic topological superconducting loops

Science.gov (United States)

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.

Lattice site occupation of insoluble impurity atoms in aluminium after implantation and irradiation

International Nuclear Information System (INIS)

Kloska, M.K.

1987-03-01

Several elements, whose atoms are oversized and insoluble in aluminium, were implanted in aluminium single crystals at different temperatures. The substitutional fraction and the lattice site location were determined using the ion-channeling technique. The substitutional fractions obtained by in situ analyses are strongly dependent on the implantation temperature. At implantation and analysis temperatures below the temperature of stage III the substitutional fraction is significant larger than at temperatures above. With increasing heat of solution the substitutional fraction decreases for all implantation temperatures. The nonsubstitutional component consists of impurity atom-vacancy complexes. These complexes are formed in the cooling phase of the cascade. At temperatures above the temperature of stage III additional free mobile vacancies were captured by the impurity atoms. The capture radius is correlated with the heat of solution and the size mismatch energy. The results constitute for the first time an experimental confirmation of molecular dynamics calculations of cascade evolution. (orig./BHO)

Hydrogenic impurity in double quantum dots

International Nuclear Information System (INIS)

Wang, X.F.

2007-01-01

The ground state binding energy and the average interparticle distances for a hydrogenic impurity in double quantum dots with Gaussian confinement potential are studied by the variational method. The probability density of the electron is calculated, too. The dependence of the binding energy on the impurity position is investigated for GaAs quantum dots. The result shows that the binding energy has a minimum as a function of the distance between the two quantum dots when the impurity is located at the center of one quantum dot or at the center of the edge of one quantum dot. When the impurity is located at the center of the two dots, the binding energy decreases monotonically

Models for impurity effects in tokamaks

International Nuclear Information System (INIS)

Hogan, J.T.

1980-03-01

Models for impurity effects in tokamaks are described with an emphasis on the relationship between attainment of high β and impurity problems. We briefly describe the status of attempts to employ neutral beam heating to achieve high β in tokamaks and propose a qualitative model for the mechanism by which heavy metal impurities may be produced in the startup phase of the discharge. We then describe paradoxes in impurity diffusion theory and discuss possible resolutions in terms of the effects of large-scale islands and sawtooth oscillations. Finally, we examine the prospects for the Zakharov-Shafranov catastrophe (long time scale disintegration of FCT equilibria) in the context of present and near-term experimental capability

Wafer-level MOCVD growth of AlGaN/GaN-on-Si HEMT structures with ultra-high room temperature 2DEG mobility

Directory of Open Access Journals (Sweden)

Xiaoqing Xu

2016-11-01

Full Text Available In this work, we investigate the influence of growth temperature, impurity concentration, and metal contact structure on the uniformity and two-dimensional electron gas (2DEG properties of AlGaN/GaN high electron mobility transistor (HEMT structure grown by metal-organic chemical vapor deposition (MOCVD on 4-inch Si substrate. High uniformity of 2DEG mobility (standard deviation down to 0.72% across the radius of the 4-inch wafer has been achieved, and 2DEG mobility up to 1740.3 cm2/V⋅s at room temperature has been realized at low C and O impurity concentrations due to reduced ionized impurity scattering. The 2DEG mobility is further enhanced to 2161.4 cm2/V⋅s which is comparable to the highest value reported to date when the contact structure is switched from a square to a cross pattern due to reduced piezoelectric scattering at lower residual strain. This work provides constructive insights and promising results to the field of wafer-scale fabrication of AlGaN/GaN HEMT on Si.

Study of impurity composition of some compounds of refractory metals by instrumental neutron activation analysis

International Nuclear Information System (INIS)

Kaganov, L.K.; Dzhumakulov, D.T.; Mukhamedshina, N.M.

1994-01-01

The compounds of refractory transition metals find wide application in all fields of engineering, in particular in microelectronics to manufacture contact-barrier layers of thin-film current-conducting systems of silicon instruments, large and very large scale integrated circuits. Production of such materials is realted with the need to apply the analytical control methods that allow to determine a large number of elements with high reliability. The instrumental neutron-activation techniques have been developed to determine impurity composition of the following compounds: MoSi 2 , WSi 2 , TiB 2 , NbB 2 , TiC, NbC

Increasing physical activity through mobile device interventions: A systematic review.

Science.gov (United States)

Muntaner, Adrià; Vidal-Conti, Josep; Palou, Pere

2016-09-01

Physical inactivity is a health problem that affects people worldwide and has been identified as the fourth largest risk factor for overall mortality (contributing to 6% of deaths globally). Many researchers have tried to increase physical activity levels through traditional methods without much success. Thus, many researchers are turning to mobile technology as an emerging method for changing health behaviours. This systematic review sought to summarise and update the existing scientific literature on increasing physical activity through mobile device interventions, taking into account the methodological quality of the studies. The articles were identified by searching the PubMed, SCOPUS and SPORTDiscus databases for studies published between January 2003 and December 2013. Studies investigating efforts to increase physical activity through mobile phone or even personal digital assistant interventions were included. The search results allowed the inclusion of 11 studies that gave rise to 12 publications. Six of the articles included in this review reported significant increases in physical activity levels. The number of studies using mobile devices for interventions has increased exponentially in the last few years, but future investigations with better methodological quality are needed to draw stronger conclusions regarding how to increase physical activity through mobile device interventions. © The Author(s) 2015.

Device for removing impurities from liquid metals

International Nuclear Information System (INIS)

Naito, Kesahiro; Yokota, Norikatsu; Shimoyashiki, Shigehiro; Takahashi, Kazuo; Ishida, Tomio.

1984-01-01

Purpose: To attain highly reliable and efficient impurity removal by forming temperature distribution the impurity removing device thereby providing the function of corrosion product trap, nuclear fission product trap and cold trap under the conditions suitable to the impurity removing materials. Constitution: The impurity removing device comprises a container containing impurity removing fillers. The fillers comprise material for removing corrosion products, material for removing nuclear fission products and material for removing depositions from liquid sodium. The positions for the respective materials are determined such that the materials are placed under the temperature conditions easy to attain their function depending on the temperature distribution formed in the removing device, whereby appropriate temperature condition is set to each of the materials. (Yoshino, Y.)

Magnetic states of single impurity in disordered environment

Directory of Open Access Journals (Sweden)

G.W. Ponedilok

2013-01-01

Full Text Available The charged and magnetic states of isolated impurities dissolved in amorphous metallic alloy are investigated. The Hamiltonian of the system under study is the generalization of Anderson impurity model. Namely, the processes of elastic and non-elastic scattering of conductive electrons on the ions of a metal and on a charged impurity are included. The configuration averaged one-particle Green's functions are obtained within Hartree-Fock approximation. A system of self-consistent equations is given for calculation of an electronic spectrum, the charged and the spin-polarized impurity states. Qualitative analysis of the effect of the metallic host structural disorder on the observed values is performed. Additional shift and broadening of virtual impurity level is caused by a structural disorder of impurity environment.

Impurity effects on ionic-liquid-based supercapacitors

International Nuclear Information System (INIS)

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

2016-01-01

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. 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.

Impurity effects on ionic-liquid-based supercapacitors

Science.gov (United States)

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.

Determination of impurity distributions in ingots of solar grade silicon by neutron activation analysis

Energy Technology Data Exchange (ETDEWEB)

Karches, Barbara; Hampel, Gabriele; Plonka, Christian; Stieghorst, Christian; Wiehl, Norbert [Mainz Univ. (Germany). Inst. for Nuclear Chemistry; Schoen, Jonas; Krenckel, Patricia; Riepe, Stephan [Fraunhofer Institute for Solar Energy Systems, Freiburg (Germany); Gerstenberg, Heiko [Technische Univ. Muenchen, Garching (Germany). Heinz-Maier-Leibniz Zentrum; Ponsard, Bernard [Belgian Nuclear Research Centre (SCK CEN), Mol (Belgium). BR2 reactor

2017-09-01

In a series of crystallization experiments, the directional solidification of silicon was investigated as a low cost path for the production of silicon wafers for solar cells. Instrumental neutron activation analysis was employed to measure the influence of different crystallization parameters on the distribution of 3d-metal impurities of the produced ingots. A theoretical model describing the involved diffusion and segregation processes during the solidification and cooling of the ingots could be verified by the experimental results. By successive etching of the samples after the irradiation, it could be shown that a layer of at least 60 μm of the samples has to be removed to get real bulk concentrations.

EUV impurity study of the Alcator tokamak

International Nuclear Information System (INIS)

Terry, J.L.; Chen, K.I.; Moos, H.W.; Marmar, E.S.

1978-01-01

The intensity of resonance line radiation from oxygen, nitrogen, carbon and molybdenum impurities has been measured in the high-field (80kG), high-density (6x10 14 cm -3 ) discharges of the Alcator Tokamak, using a 0.4-m normal-incidence monochromator (300-1300A) with its line of sight fixed along a major radius. Total light-impurity concentrations of a few tenths of a percent have been estimated by using both a simple model and a computer code which included Pfirsch-Schlueter impurity diffusion. The resulting values of Zsub(eff), including the contributions due to both the light impurities and molybdenum, were close to one. The power lost through the impurity line radiation from the lower ionization states accounted for approximately 10% of the total Ohmic input power at high densities. (author)

Interactions of impurities with a moving grain boundary

Energy Technology Data Exchange (ETDEWEB)

Bauer, C L [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA)

1975-01-01

Most theories developed to explain interaction of impurities with a moving grain boundary involve a uniform excess impurity concentration distributed along a planar grain boundary. As boundary velocity increases, the excess impurities exert a net drag force on the boundary until a level is reached whereat the drag force no longer can balance the driving force and breakaway of the boundary from these impurities occurs. In this investigation, assumptions of a uniform lateral impurity profile and a planar grain boundary shape are relaxed by allowing both forward and lateral diffusion of impurities in the vicinity of a grain boundary. It is found that the two usual regions (drag of impurities by, and breakaway of a planar grain boundary) are separated by an extensive region wherein a uniform lateral impurity profile and a planar grain boundary shape are unstable. It is suspected that, in this unstable region, grain boundaries assume a spectrum of more complex morphologies and that elucidation of these morphologies can provide the first definitive description of the breakaway process and insight to more complex phenomena such as solid-solution strengthening, grain growth and secondary recrystallization.

Lattice dynamics of impurity clusters : application to pairs

International Nuclear Information System (INIS)

Chandralekha Devi, N.; Behera, S.N.

1979-01-01

A general solution is obtained for the lattice dynamics of a cluster of n-impurity atoms using the double-time Green's function formalism. The cluster is characterized by n-mass defect and m-force constant change parameters. It is shown that this general solution for the Green's function for the n-impurity cluster can also be expressed in terms of the Green's function for the (n-1)-impurity cluster. As an application, the cluster impurity modes for a pair are calculated using the Debye model for the host lattice dynamics. The splitting of the high frequency local modes and nearly zero frequency resonant modes due to pairs show an oscillatory behaviour on varying the distance of separation between the two impurity atoms. These oscillations are most prominent for two similar impurities and get damped for two dissimilar impurities or if one of the impurities produces a force constant change. The predictions of the calculation provide qualitative explanation of the data obtained from the infrared measurements of the resonant modes in mixed crystal system of KBrsub(1-c)Clsub(c):Lisup(+) and KBrsub(1-c)Isub(c):Lisup(+). (author)

Impurity transport in the Wendelstein VII-A stellarator

International Nuclear Information System (INIS)

1985-01-01

Impurity radiation losses in net-current-free neutral-beam-heated plasmas in the Wendelstein W VII-A stellarator are the combined effect of particularly strong impurity sources and improved particle confinement as compared with ohmically heated tokamak-like plasma discharges. Experiments are described and conclusions are drawn about the impurity species, their origin and their transport behaviour. The impurity transport is modelled by a 1-D impurity transport and radiation code. The evolution of the total radiation in time and space deduced from soft-X-ray and bolometer measurements can be fairly well simulated by the code. Experimentally, oxygen was found to make the main contribution to the radiation losses. In the calculations, an influx of cold oxygen desorbed from the walls of the order of 10 13 -10 14 cm -2 .s -1 and a rate of fast injected oxygen corresponding to a 1% impurity content of the neutral beams in combination with neoclassical impurity transport leads to quantitative agreement between the simulation and the observed radiation. The transport of A1 trace impurities injected by the laser blow-off technique was experimentally studied by soft-X-ray measurements using a differential method allowing extraction of the time evolution of A1 XII, XIII radial profiles. These are compared with code predictions, together with additional spectroscopic measurements. The main features of the impurity transport are consistent with neoclassical predictions, which explain particularly the central impurity accumulation. Some details, however, seem to require additional 'anomalous' transport. Such an enhancement is correlated with distortions of the magnetic configuration around resonant magnetic surfaces. (author)

Uranium analysis. Impurities determination by spark mass spectrometry

International Nuclear Information System (INIS)

Anon.

Determination of impurities in uranium, suitable for atomic content greater than 10 -8 , particularly adapted for a low content. The method is quantitative for metallic impurities and qualitative for non metallic impurities [fr

Fluid and gyrokinetic simulations of impurity transport at JET

DEFF Research Database (Denmark)

Nordman, H; Skyman, A; Strand, P

2011-01-01

Impurity transport coefficients due to ion-temperature-gradient (ITG) mode and trapped-electron mode turbulence are calculated using profile data from dedicated impurity injection experiments at JET. Results obtained with a multi-fluid model are compared with quasi-linear and nonlinear gyrokinetic...... simulation results obtained with the code GENE. The sign of the impurity convective velocity (pinch) and its various contributions are discussed. The dependence of the impurity transport coefficients and impurity peaking factor −∇nZ/nZ on plasma parameters such as impurity charge number Z, ion logarithmic...

Stability-indicating HPLC-DAD/UV-ESI/MS impurity profiling of the anti-malarial drug lumefantrine.

Science.gov (United States)

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.

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

Science.gov (United States)

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.

Method for detecting trace impurities in gases

Science.gov (United States)

Freund, S.M.; Maier, W.B. II; Holland, R.F.; Beattie, W.H.

A technique for considerably improving the sensitivity and specificity of infrared spectrometry as applied to quantitative determination of trace impurities in various carrier or solvent gases is presented. A gas to be examined for impurities is liquefied and infrared absorption spectra of the liquid are obtained. Spectral simplification and number densities of impurities in the optical path are substantially higher than are obtainable in similar gas-phase analyses. Carbon dioxide impurity (approx. 2 ppM) present in commercial Xe and ppM levels of Freon 12 and vinyl chloride added to liquefied air are used to illustrate the method.

Process and system for removing impurities from a gas

Science.gov (United States)

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.

Impurity control in TFTR

International Nuclear Information System (INIS)

Cecchi, J.L.

1980-06-01

The control of impurities in TFTR will be a particularly difficult problem due to the large energy and particle fluxes expected in the device. As part of the TFTR Flexibility Modification (TEM) project, a program has been implemented to address this problem. Transport code simulations are used to infer an impurity limit criterion as a function of the impurity atomic number. The configurational designs of the limiters and associated protective plates are discussed along with the consideration of thermal and mechanical loads due to normal plasma operation, neutral beams, and plasma disruptions. A summary is given of the materials-related research, which has been a collaborative effort involving groups at Argonne National Laboratory, Sandia Laboratories, and Princeton Plasma Physics Laboratory. Conceptual designs are shown for getterng systems capable of regenerating absorbed tritium. Research on this topic by groups at the previously mentioned laboratories and SAES Research Laboratory is reviewed

Local chemistry of Al and P impurities in silica

DEFF Research Database (Denmark)

Lægsgaard, Jesper; Stokbro, Kurt

2000-01-01

The local structure around Al and P impurities in silica is investigated using density-functional theory. Two distinct cases are considered: impurities substituting for a Si atom in alpha quartz, and impurities implanted in a stoichiometric alpha-quartz crystal. Both impurity elements are found t...

Impurity transport in internal transport barrier discharges on JET

International Nuclear Information System (INIS)

Dux, R.; Giroud, C.; Zastrow, K.-D.

2004-01-01

Impurity behaviour in JET internal transport barrier (ITB) discharges with reversed shear has been investigated. Metallic impurities accumulate in cases with too strong peaking of the main ion density profile. The accumulation is due to inwardly directed drift velocities inside the ITB radius. The strength of the impurity peaking increases with the impurity charge and is low for the low-Z elements C and Ne. Transport calculations show that the observed behaviour is consistent with dominant neoclassical impurity transport inside the ITB. In some cases, MHD events in the core flatten the radial profile of the metallic impurity. (author)

Children's active travel and independent mobility in four countries

DEFF Research Database (Denmark)

Fyhri, Aslak; Hjorthol, Randi; Mackett, Roger L.

2011-01-01

In many countries a decline in children's active and independent mobility, like walking and cycling is registered. In this paper the development of children's mobility in Denmark, Finland, Great Britain and Norway is compared to examine differences and similarities in these countries. Accessible ...

Mobile Collaborative Informal Learning Design: Study of collaborative effectiveness using Activity Theory

Directory of Open Access Journals (Sweden)

Hasnain Zafar Baloch

2012-07-01

Full Text Available Smart Mobile Devices (SMD are there for many years but using them as learning tools started to emerge as new research area. The trend to merge collaborative learning methodology by using mobile devices in informal context is important for implementation of Learner Centric Learning (LCL. Survey and numerous studies show that more than 95% of students in colleges are users of these smart mobile devices in developed world. Developing counties are also catching up and we can see this percentage is almost same in university level in these countries. Students are using SMDs for learning in some form. Higher education Institutions also try to embark their E-learning to Mobile learning (ML. The aim of this paper is to do propose operational framework for designing Mobile Collaborative Informal learning activities using SMDs. Show results of experimental and case study done to study the Mobile Collaborative Informal learning using Activity Theory (AT. Core Components of framework are Mobile Learning Activities/Objects, Wireless/Mobile Smart devices, Collaborative knowledge and Collaborative learning. The research mention here is its infancy stage.

Local order dependent impurity levels in alloy semiconductors

International Nuclear Information System (INIS)

Silva, C.E.T.G. da; Ecole Normale Superieure, 75 - Paris

1981-01-01

We develop a one band/may sites model for an isoelectronic impurity in a semiconductor alloy. The cluster-Bethe-lattice approximation is used to study the dependence of the impurity energy level upon the short range order (SRO) of the alloy. The Kikuchi parametrization is used to describe the latter. We take into account diagonal disorder only, with possible off-diagonal relaxation around the impurity site. All the inequivalent clusters of the impurity site and its first nearest neighbours are considered, thus including the important short range alloy potential fluctuations. Results are presented for the local density of impurity states, for different degrees of SRO in the alloy. (Author) [pt

Achieving improved ohmic confinement via impurity injection

International Nuclear Information System (INIS)

Bessenrodt-Weberpals, M.; Soeldner, F.X.

1991-01-01

Improved Ohmic Confinement (IOC) was obtained in ASDEX after a modification of the divertors that allowed a larger (deuterium and impurity) backflow from the divertor chamber. The quality of IOC depended crucially on the wall conditions, i.e. IOC was best for uncovered stainless steels walls and vanished with boronization. Furthermore, IOC was found only in deuterium discharges. These circumstances led to the idea that IOC correlates with the content of light impurities in the plasma. To substantiate this working hypothesis, we present observations in deuterium discharges with boronized wall conditions into which various impurities have been injected with the aim to induce IOC conditions. Firstly, the plasma behaviour in typical IOC discharges is characterized. Secondly, injection experiments with the low-Z impurities nitrogen and neon as well as with the high-Z impurities argon and krypton are discussed. Then, we concentrate on optimized neon puffing that yields the best confinement results which are similar to IOC conditions. Finally, these results are compared with eperiments in other tokamaks and some conclusions are drawn about the effects of the impurity puffing on both, the central and the edge plasma behaviour. (orig.)

A Survey of Online Activity Recognition Using Mobile Phones

Directory of Open Access Journals (Sweden)

Muhammad Shoaib

2015-01-01

Full Text Available Physical activity recognition using embedded sensors has enabled many context-aware applications in different areas, such as healthcare. Initially, one or more dedicated wearable sensors were used for such applications. However, recently, many researchers started using mobile phones for this purpose, since these ubiquitous devices are equipped with various sensors, ranging from accelerometers to magnetic field sensors. In most of the current studies, sensor data collected for activity recognition are analyzed offline using machine learning tools. However, there is now a trend towards implementing activity recognition systems on these devices in an online manner, since modern mobile phones have become more powerful in terms of available resources, such as CPU, memory and battery. The research on offline activity recognition has been reviewed in several earlier studies in detail. However, work done on online activity recognition is still in its infancy and is yet to be reviewed. In this paper, we review the studies done so far that implement activity recognition systems on mobile phones and use only their on-board sensors. We discuss various aspects of these studies. Moreover, we discuss their limitations and present various recommendations for future research.

A Survey of Online Activity Recognition Using Mobile Phones

Science.gov (United States)

Shoaib, Muhammad; Bosch, Stephan; Incel, Ozlem Durmaz; Scholten, Hans; Havinga, Paul J.M.

2015-01-01

Physical activity recognition using embedded sensors has enabled many context-aware applications in different areas, such as healthcare. Initially, one or more dedicated wearable sensors were used for such applications. However, recently, many researchers started using mobile phones for this purpose, since these ubiquitous devices are equipped with various sensors, ranging from accelerometers to magnetic field sensors. In most of the current studies, sensor data collected for activity recognition are analyzed offline using machine learning tools. However, there is now a trend towards implementing activity recognition systems on these devices in an online manner, since modern mobile phones have become more powerful in terms of available resources, such as CPU, memory and battery. The research on offline activity recognition has been reviewed in several earlier studies in detail. However, work done on online activity recognition is still in its infancy and is yet to be reviewed. In this paper, we review the studies done so far that implement activity recognition systems on mobile phones and use only their on-board sensors. We discuss various aspects of these studies. Moreover, we discuss their limitations and present various recommendations for future research. PMID:25608213

Influence of impurities on the crystallization of dextrose monohydrate

Science.gov (United States)

Markande, Abhay; Nezzal, Amale; Fitzpatrick, John; Aerts, Luc; Redl, Andreas

2012-08-01

The effects of impurities on dextrose monohydrate crystallization were investigated. Crystal nucleation and growth kinetics in the presence of impurities were studied using an in-line focused beam reflectance monitoring (FBRM) technique and an in-line process refractometer. Experimental data were obtained from runs carried out at different impurity levels between 4 and 11 wt% in the high dextrose equivalent (DE) syrup. It was found that impurities have no significant influence on the solubility of dextrose in water. However, impurities have a clear influence on the nucleation and growth kinetics of dextrose monohydrate crystallization. Nucleation and growth rate were favored by low levels of impurities in the syrup.

Striped morphologies induced by magnetic impurities in d-wave superconductors

International Nuclear Information System (INIS)

Zuo Xianjun

2011-01-01

Research Highlights: → We investigate striped morphologies induced by magnetic impurities in d-wave superconductors (DSCs). → For the single-impurity and two-impurity cases, modulated checkerboard pattern and stripe-like structures are induced. → When more magnetic impurities are inserted, more complex modulated structures could be induced, including rectilinear and right-angled stripes and quantum-corral-like structures. → Impurities could induce complex striped morphologies in DSCs. - Abstract: We study striped morphologies induced by magnetic impurities in d-wave superconductors (DSCs) near optimal doping by self-consistently solving the Bogoliubov-de Gennes equations based on the t - t' - U - V model. For the single-impurity case, it is found that the stable ground state is a modulated checkerboard pattern. For the two-impurity case, the stripe-like structures in order parameters are induced due to the impurity-pinning effect. The modulations of DSC and charge orders share the same period of four lattice constants (4a), which is half the period of modulations in the coexisting spin order. Interestingly, when three or more impurities are inserted, the impurities could induce more complex striped morphologies due to quantum interference. Further experiments of magnetic impurity substitution in DSCs are expected to check these results.

Interstitial impurity interactions and dislocation microdynamics in Mo crystals

International Nuclear Information System (INIS)

Kwok, D.N.

1975-05-01

The effects of interstitial impurities on the mechanical properties of molybdenum are explored by comparing results obtained for crystals of various interstitial contents controlled by ultra-high vacuum outgassing. Results show a modulus reduction for as-grown samples and for outgassed specimens at low applied stresses. As a function of plastic microstrain, the values of modulus defect for both as-grown and outgassed specimens saturate at the same value. Interstitial impurities act as pinning agents to dislocation bowing, but when all the easy dislocation loops have broken away from local interstitial pins, the modulus defect reaches a constant saturation value. Etch pitting techniques were used to correlate microstrain observations with dislocation generation and motion. It has been found that edge dislocation generation and movement are active in the microstrain region while screw dislocations are relatively inactive until the macrostrain region is reached. Dislocation velocities range from 10 -6 to 10 -3 cm/s and the average distance between interstitial impurity pinning points is found to be approximately 8 x 10 -4 cm. (U.S.)

Professional Mobility as the Realization Factor of Teacher’s Innovative Activity

Directory of Open Access Journals (Sweden)

S. A. Morozova

2015-02-01

Full Text Available The article deals with the teachers’ professional mobility as a factor of their readiness for innovative activity. Based on the analysis of psychological and pe- dagogic literature, the essence and structure of the given phenomenon are defined. The subject of the experimental research compiles the key qualities of profes- sional mobility and their development techniques for vocational training teachers. The aim of the study includes the identification of the key characteristics of the qualities in question. The main methodological idea is defined as follows: the professional mobility formation is the basis of teachers’ productive innovative activity. The research findings made it possible to identify the components of profes- sional mobility: innovative attitude, creativity, intellectual mobility, extra-normative ac- tivity and communication skills. The research results provide the basis for effective technologies selection for developing teachers’ professional mobility. 

Professional Mobility as the Realization Factor of Teacher’s Innovative Activity

Directory of Open Access Journals (Sweden)

S. A. Morozova

2012-01-01

Full Text Available The article deals with the teachers’ professional mobility as a factor of their readiness for innovative activity. Based on the analysis of psychological and pe- dagogic literature, the essence and structure of the given phenomenon are defined. The subject of the experimental research compiles the key qualities of profes- sional mobility and their development techniques for vocational training teachers. The aim of the study includes the identification of the key characteristics of the qualities in question. The main methodological idea is defined as follows: the professional mobility formation is the basis of teachers’ productive innovative activity. The research findings made it possible to identify the components of profes- sional mobility: innovative attitude, creativity, intellectual mobility, extra-normative ac- tivity and communication skills. The research results provide the basis for effective technologies selection for developing teachers’ professional mobility. 

Characteristics of post-disruption runaway electrons with impurity pellet injection

International Nuclear Information System (INIS)

Kawano, Yasunori; Nakano, Tomohide; Isayama, Akihiko; Asakura, Nobuyuki; Tamai, Hiroshi; Kubo, Hirotaka; Takenaga, Hidenobu; Bakhtiari, Mohammad; Ide, Shunsuke; Kondoh, Takashi; Hatae, Takaki

2005-01-01

Characteristics of post-disruption runaway electrons with impurity pellet injection were investigated for the first time using the JT-60U tokamak device. A clear deposition of impurity neon ice pellets was observed in a post-disruption runaway plasma. The pellet ablation was attributed to the energy deposition of relativistic runaway electrons in the pellet. A high normalized electron density was stably obtained with n e bar /n GW ∼2.2. Effects of prompt exhaust of runaway electrons and reduction of runaway plasma current without large amplitude MHD activities were found. One possible explanation for the basic behavior of runaway plasma current is that it follows the balance of avalanche generation of runaway electrons and slowing down predicted by the Andersson-Helander model, including the combined effect of collisional pitch angle scattering and synchrotron radiation. Our results suggested that the impurity pellet injection reduced the energy of runaway electrons in a stepwise manner. (author)

Separation and determination of synthetic impurities of difloxacin by reversed-phase high-performance liquid chromatography.

Science.gov (United States)

Rao, R Nageswara; Nagaraju, V

2004-11-19

A simple and rapid reversed-phase high-performance liquid chromatographic method for separation and determination of process-related impurities of difloxacin (DFL) was developed. The separation was achieved on a reversed-phase C(18) column using methanol-water-acetic acid (78:21.9:0.1, v/v/v) as a mobile solvent at a flow rate of 1.0 ml/min at 28 degrees C using UV detection at 230 nm. It was linear over a range of 0.03 x 10(-6) to 1.60 x 10(-6)g for process related impurities and 0.05 x 10(-6) to 2.40 x 10(-6)g for difloxacin. The detection limits were 0.009 x 10(-6) to 0.024 x 10(-6)g for all the compounds examined. The recoveries were found to be in the range of 97.6-102.0% for impurities as well as difloxacin. The precision and robustness of the method were evaluated. It was used for not only quality assurance, but also monitoring the synthetic reactions involved in the process development work of difloxacin. The method was found to be specific, precise and reliable for the determination of unreacted levels of raw materials, intermediates in the reaction mixtures and the finished products of difloxacin.

Impurity screening of scrape-off plasma in a tokamak

International Nuclear Information System (INIS)

Kishimoto, Hiroshi; Tani, Keiji; Nakamura, Hiroo

1981-11-01

Impurity screening effect of a scrape-off layer has been studied in a tokamak, based on a simple model of wall-released impurity behavior. Wall-sputtered impurities are stopped effectively by the scrape-off plasma for a medium-Z or high-Z wall system while major part of impurities enters the main plasma in a low-Z wall system. The screening becomes inefficient with increase of scrape-off plasma temperature. Successive multiplication of recycling impurities in the scrape-off layer is large for a high-Z wall and is enhanced by a rise of scrape-off plasma temperature. The stability of plasma-wall interaction is determined by a multiplication factor of recycling impurities. (author)

Observation of impurity accumulation and concurrent impurity influx in PBX

International Nuclear Information System (INIS)

Sesnic, S.S.; Fonck, R.J.; Ida, K.; Couture, P.; Kaita, R.; Kaye, S.; Kugel, H.; LeBlanc, B.; Okabayashi, M.; Paul, S.; Powell, E.T.; Reusch, M.; Takahashi, H.; Gammel, G.; Morris, W.

1987-01-01

Impurity studies in L- and H-mode discharges in PBX have shown that both types of discharges can evolve into either an impurity accumulative or nonaccumulative case. In a typical accumulative discharge, Z eff peaks in the center to values of about 5. The central metallic densities can be high, n met /n e ≅ 0.01, resulting in central radiated power densities in excess of 1 W/cm 3 , consistent with bolometric estimates. The radial profiles of metals obtained independently from the line radiation in the soft X-ray and the VUV regions are very peaked. Concurrent with the peaking, an increase in the impurity influx coming from the edge of the plasma is observed. At the beginning of the accumulation phase the inward particle flux for titanium has values of 6x10 10 and 10x10 10 particles/cm 2 s at minor radii of 6 and 17 cm. At the end of the accumulation phase, this particle flux is strongly increased to values of 3x10 12 and 1x10 12 particles/cm 2 s. This increased flux is mainly due to influx from the edge of the plasma and to a lesser extent due to increased convective transport. Using the measured particle flux, an estimate of the diffusion coefficient D and the convective velocity v is obtained. (orig.)

Impurity induced resistivity upturns in underdoped cuprates

Energy Technology Data Exchange (ETDEWEB)

Das, Nabyendu, E-mail: nabyendudas@gmail.com; Singh, Navinder

2016-01-28

Impurity induced low temperature upturns in both the ab-plane and the c-axis dc-resistivities of cuprates in the pseudogap state have been observed in experiments. We provide an explanation of this phenomenon by incorporating impurity scattering of the charge carriers within a phenomenological model proposed by Yang, Rice and Zhang. The scattering between charge carriers and the impurity atom is considered within the lowest order Born approximation. Resistivity is calculated within Kubo formula using the impurity renormalized spectral functions. Using physical parameters for cuprates, we describe qualitative features of the upturn phenomena and its doping evolution that coincides with the experimental findings. We stress that this effect is largely due to the strong electronic correlations.

Impurity induced resistivity upturns in underdoped cuprates

International Nuclear Information System (INIS)

Das, Nabyendu; Singh, Navinder

2016-01-01

Impurity induced low temperature upturns in both the ab-plane and the c-axis dc-resistivities of cuprates in the pseudogap state have been observed in experiments. We provide an explanation of this phenomenon by incorporating impurity scattering of the charge carriers within a phenomenological model proposed by Yang, Rice and Zhang. The scattering between charge carriers and the impurity atom is considered within the lowest order Born approximation. Resistivity is calculated within Kubo formula using the impurity renormalized spectral functions. Using physical parameters for cuprates, we describe qualitative features of the upturn phenomena and its doping evolution that coincides with the experimental findings. We stress that this effect is largely due to the strong electronic correlations.

Low Z impurity transport in tokamaks. [Neoclassical transport theory

Energy Technology Data Exchange (ETDEWEB)

Hawryluk, R.J.; Suckewer, S.; Hirshman, S.P.

1978-10-01

Low Z impurity transport in tokamaks was simulated with a one-dimensional impurity transport model including both neoclassical and anomalous transport. The neoclassical fluxes are due to collisions between the background plasma and impurity ions as well as collisions between the various ionization states. The evaluation of the neoclassical fluxes takes into account the different collisionality regimes of the background plasma and the impurity ions. A limiter scrapeoff model is used to define the boundary conditions for the impurity ions in the plasma periphery. In order to account for the spectroscopic measurements of power radiated by the lower ionization states, fluxes due to anomalous transport are included. The sensitivity of the results to uncertainties in rate coefficients and plasma parameters in the periphery are investigated. The implications of the transport model for spectroscopic evaluation of impurity concentrations, impurity fluxes, and radiated power from line emission measurements are discussed.

Light impurity production in tokamaks

International Nuclear Information System (INIS)

Philipps, V.; Vietzke, E.; Erdweg, M.

1989-01-01

A review is given of the different erosion processes of carbon materials with special emphasis on conditions relevant to plasma surface interactions. New results on the chemical erosion and radiation enhanced sublimation of boron-carbon layers are presented. The chemical hydrocarbon formation produced by the interaction of the TEXTOR scrape-off plasma with a carbon target has been investigated up to temperatures of 1500K using a Sniffer probe. The chemical interaction of the plasma with the carbon walls in TEXTOR is also analysed by measuring the hydrocarbon and CO and CO 2 partial pressures built up on the surrounding walls during the discharges. The recycling of oxygen impurities in an all carbon surrounding occurs predominantly in the form of CO and Co 2 molecules and the analysis of both neutral pressures during the discharges has been used as an additional diagnostic for the oxygen impurity situation in TEXTOR. These data are discussed in view of spectroscopic measurements on the influx of carbon and oxygen atoms from the walls and impurity line radiation. CD-band spectroscopy in addition is employed to identify the hydrocarbon chemical carbon erosion. Our present understanding of the oxygen impurity recycling and the oxygen sources are described. Particle induced release of CO molecules from the entire first wall is believed to be the dominant influx process of oxygen in the SOL of plasmas with carbon facing materials. The influence of coating the TEXTOR first wall with a boron-carbon film (B/C ≅1) on the light impurity behaviour is shown. (author)

Application of Analytical Quality by Design concept for bilastine and its degradation impurities determination by hydrophilic interaction liquid chromatographic method.

Science.gov (United States)

Terzić, Jelena; Popović, Igor; Stajić, Ana; Tumpa, Anja; Jančić-Stojanović, Biljana

2016-06-05

This paper deals with the development of hydrophilic interaction liquid chromatographic (HILIC) method for the analysis of bilastine and its degradation impurities following Analytical Quality by Design approach. It is the first time that the method for bilastine and its impurities is proposed. The main objective was to identify the conditions where an adequate separation in minimal analysis duration could be achieved within a robust region. Critical process parameters which have the most influence on method performance were defined as acetonitrile content in the mobile phase, pH of the aqueous phase and ammonium acetate concentration in the aqueous phase. Box-Behnken design was applied for establishing a relationship between critical process parameters and critical quality attributes. The defined mathematical models and Monte Carlo simulations were used to identify the design space. Fractional factorial design was applied for experimental robustness testing and the method is validated to verify the adequacy of selected optimal conditions: the analytical column Luna(®) HILIC (100mm×4.6mm, 5μm particle size); mobile phase consisted of acetonitrile-aqueous phase (50mM ammonium acetate, pH adjusted to 5.3 with glacial acetic acid) (90.5:9.5, v/v); column temperature 30°C, mobile phase flow rate 1mLmin(-1), wavelength of detection 275nm. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of affordable technology on physical activity levels and mobility outcomes in rehabilitation: a protocol for the Activity and MObility UsiNg Technology (AMOUNT) rehabilitation trial.

Science.gov (United States)

Hassett, Leanne; van den Berg, Maayken; Lindley, Richard I; Crotty, Maria; McCluskey, Annie; van der Ploeg, Hidde P; Smith, Stuart T; Schurr, Karl; Killington, Maggie; Bongers, Bert; Howard, Kirsten; Heritier, Stephane; Togher, Leanne; Hackett, Maree; Treacy, Daniel; Dorsch, Simone; Wong, Siobhan; Scrivener, Katharine; Chagpar, Sakina; Weber, Heather; Pearson, Ross; Sherrington, Catherine

2016-06-06

People with mobility limitations can benefit from rehabilitation programmes that provide a high dose of exercise. However, since providing a high dose of exercise is logistically challenging and resource-intensive, people in rehabilitation spend most of the day inactive. This trial aims to evaluate the effect of the addition of affordable technology to usual care on physical activity and mobility in people with mobility limitations admitted to inpatient aged and neurological rehabilitation units compared to usual care alone. A pragmatic, assessor blinded, parallel-group randomised trial recruiting 300 consenting rehabilitation patients with reduced mobility will be conducted. Participants will be individually randomised to intervention or control groups. The intervention group will receive technology-based exercise to target mobility and physical activity problems for 6 months. The technology will include the use of video and computer games/exercises and tablet applications as well as activity monitors. The control group will not receive any additional intervention and both groups will receive usual inpatient and outpatient rehabilitation care over the 6-month study period. The coprimary outcomes will be objectively assessed physical activity (proportion of the day spent upright) and mobility (Short Physical Performance Battery) at 6 months after randomisation. Secondary outcomes will include: self-reported and objectively assessed physical activity, mobility, cognition, activity performance and participation, utility-based quality of life, balance confidence, technology self-efficacy, falls and service utilisation. Linear models will assess the effect of group allocation for each continuously scored outcome measure with baseline scores entered as a covariate. Fall rates between groups will be compared using negative binomial regression. Primary analyses will be preplanned, conducted while masked to group allocation and use an intention-to-treat approach. The

Assessment of a Mobile Game ("MobileKids Monster Manor") to Promote Physical Activity Among Children.

Science.gov (United States)

Garde, Ainara; Umedaly, Aryannah; Abulnaga, S Mazdak; Robertson, Leah; Junker, Anne; Chanoine, Jean Pierre; Ansermino, J Mark; Dumont, Guy A

2015-04-01

The majority of children in North America are not meeting current physical activity guidelines. The purpose of this study was to evaluate the impact of a mobile phone game ("MobileKids Monster Manor") as a tool to promote voluntary physical activity among children. The game integrates data from an accelerometer-based activity monitor (Tractivity(®); Kineteks Corp., Vancouver, BC, Canada) wirelessly connected to a phone and was developed with the involvement of a team of young advisors (KidsCan Initiative: Involving Youth as Ambassadors for Research). Fifty-four children 8-13 years old completed a week of baseline data collection by wearing an accelerometer but receiving no feedback about their activity levels. The 54 children were then sequentially assigned to two groups: One group played "MobileKids Monster Manor," and the other received daily activity feedback (steps and active minutes) via an online program. The physical activity (baseline and intervention weeks) was measured using the activity monitor and compared using two-way repeated-measures analysis of variance (intervention×time). Forty-seven children with a body mass index (BMI) z-score of 0.35±1.18 successfully completed the study. Significant (P=0.01) increases in physical activity were observed during the intervention week in both the game and feedback groups (1191 and 796 steps/day, respectively). In the game group, greater physical activity was demonstrated in children with higher BMI z-score, showing 964 steps/day more per BMI z-score unit (P=0.03; 95 percent confidence interval of 98 to 1829). Further investigation is required to confirm that our game design promotes physical activity.

Mobility activation in thermally deposited CdSe thin films

Indian Academy of Sciences (India)

Effect of illumination on mobility has been studied from the photocurrent decay characteristics of thermally evaporated CdSe thin films deposited on suitably cleaned glass substrate held at elevated substrate temperatures. The study indicates that the mobilities of the carriers of different trap levels are activated due to the ...

Control Strategy for Small Molecule Impurities in Antibody-Drug Conjugates.

Science.gov (United States)

Gong, Hai H; Ihle, Nathan; Jones, Michael T; Kelly, Kathleen; Kott, Laila; Raglione, Thomas; Whitlock, Scott; Zhang, Qunying; Zheng, Jie

2018-04-01

Antibody-drug conjugates (ADCs) are an emerging class of biopharmaceuticals. As such, there are no specific guidelines addressing impurity limits and qualification requirements. The current ICH guidelines on impurities, Q3A (Impurities in New Drug Substances), Q3B (Impurities in New Drug Products), and Q6B (Specifications: Test Procedures and Acceptance Criteria for Biotechnological/Biological Products) do not adequately address how to assess small molecule impurities in ADCs. The International Consortium for Innovation and Quality in Pharmaceutical Development (IQ) formed an impurities working group (IWG) to discuss this issue. This white paper presents a strategy for evaluating the impact of small molecule impurities in ADCs. This strategy suggests a science-based approach that can be applied to the design of control systems for ADC therapeutics. The key principles that form the basis for this strategy include the significant difference in molecular weights between small molecule impurities and the ADC, the conjugation potential of the small molecule impurities, and the typical dosing concentrations and dosing schedule. The result is that exposure to small impurities in ADCs is so low as to often pose little or no significant safety risk.

Impurity transport in internal transport barrier discharges on JET

International Nuclear Information System (INIS)

Dux, R.

2002-01-01

In JET plasmas with internal transport barrier (ITB) the behaviour of metallic and low-Z impurities (C, Ne) was investigated. In ITB discharges with reversed shear, the metallic impurities accumulate in cases with too strong peaking of the density profile, while the concentration of low-Z elements C and Ne is only mildly peaked. The accumulation might be so strong, that the central radiation approximately equals the central heating power followed by a radiative collapse of the transport barrier. The radial location with strong impurity gradients (convective barrier) was identified to be situated inside (not at!) the heat flux barrier. Calculations of neo-classical transport were performed for these discharges, including impurity-impurity collisions. It was found, that the observed Z-dependence of the impurity peaking and the location of the impurity 'barrier' can be explained with neo-classical transport. ITB discharges with monotonic shear show less inward convection and seem to be advantageous with respect to plasma purity. (author)

Microscopic models of impurities in silicon

International Nuclear Information System (INIS)

Assali, L.V.C.

1985-01-01

The study of electronic structure of insulated and complex puntual impurities in silicon responsible by the appearing of deep energy levels in the forbiden band of semiconductor, is presented. The molecular cluster model with the treatment of surface orbitals by Watson sphere within the formalism of Xα multiple scattering method, was used. The electronic structures of three clusters representative of perfect silicon crystal, which were used for the impurity studies, are presented. The method was applied to analyse insulated impurities of substitutional and interstitial hydrogen (Si:H and Si:H i ), subtitutional and interstitial iron in neutral and positive charge states (Si:Fe 0 , + , Si:Fe 0 , + ) and substitutional gold in three charge states(Si,Au - , 0 , + ). The thetraedic interstitial defect of silicon (Si:Si i ) was also studied. The complex impurities: neighbour iron pair in the lattice (Si:Fe 2 ), substitutional gold-interstitial iron pair (Si:Au s Fe) and substitutional boron-interstitial hydrogen pair (Si:B s H i ), were analysed. (M.C.K.) [pt

The Effectiveness of WhatsApp Mobile Learning Activities Guided by Activity Theory on Students' Knowledge Management

Science.gov (United States)

Barhoumi, Chokri

2015-01-01

This research paper explores the effectiveness of using mobile technologies to support a blended learning course titled Scientific Research Methods in Information Science. Specifically, it discusses the effects of WhatsApp mobile learning activities guided by activity theory on students' knowledge Management (KM). During the 2014 academic year,…

Observations of long impurity confinement times in the ISX tokamak

Energy Technology Data Exchange (ETDEWEB)

Burrell, K H; Wong, S K; Muller, III, C H; Hacker, M P [General Atomic Co., San Diego, CA (USA); Ketterer, H E; Isler, R C; Lazarus, E A [Oak Ridge National Lab., TN (USA)

1981-08-01

The transport of small amounts of silicon and aluminium injected into plasmas in the Impurity Study Experiment (ISX) tokamak is studied. By monitoring the time behaviour of ultra-violet spectral lines emitted by various charge states of those impurities and comparing this behaviour to the predictions of a multi-species impurity transport code, it is found that both impurity penetration times and impurity containment times are consistent with neoclassical predictions. The observed impurity containment times, which are greater than three times the energy containment time, are consistent with the inward convection predicted by neoclassical theory.

Numerical studies of impurities in fusion plasmas

International Nuclear Information System (INIS)

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

Impurity Trapping of Positive Muons in Metals

CERN Multimedia

2002-01-01

Polarized positive muons are implanted into metal samples. In an applied magnetic field the muon spin precession is studied. The line width in the precession frequency spectrum gives information about the static and dynamic properties of muons in a metal lattice. At temperatures where the muon is immobile within its lifetime the line width gives information about the site of location. At temperatures where the muon is mobile, the line width gives information on the diffusion process. It is known from experiments on quasi-elastic neutron scattering on hydrogen in niobium that interstitial impurities like nitrogen tend to act as traps for hydrogen. These trapping effects have now been studied systematically for muons in both f.c.c. metals (aluminium and copper) and b.c.c. metals (mainly niobium). Direct information on the trapping rates and the nature of the diffusion processes can be obtained since the muonic lifetime covers a time range where many of these processes occur.\\\\ \\\\ Mathematical models are set up ...

Impurity study of TMX using ultraviolet spectroscopy

International Nuclear Information System (INIS)

Allen, S.L.; Strand, O.T.; Moos, H.W.; Fortner, R.J.; Nash, T.J.; Dietrich, D.D.

1981-01-01

An extreme ultraviolet (EUV) study of the emissions from intrinsic and injected impurities in TMX is presented. Two survey spectrographs were used to determine that the major impurities present were oxygen, nitrogen, carbon, and titanium. Three absolutely-calibrated monochromators were used to measure the time histories and radial profiles of these impurity emissions in the central cell and each plug. Two of these instruments were capable of obtaining radial profiles as a function of time in a single shot

Scattering and mobility in indium gallium arsenide channel, pseudomorphic high electron mobility transistors (InGaAs pHEMTs)

International Nuclear Information System (INIS)

Pearson, J.L.

1999-03-01

with intermediate (5nm) and thin (2.5nm) spacers, was never found to dominate. As has been reported for similar structures, anisotropy of transport mobility was found, with the [011] direction having a higher mobility than the [011-bar] direction ((100) GaAs substrate nominally aligned ±0.1 deg.). Intermediate directions had intermediate mobilities. The anisotropy increased with indium content and growth temperature, and persisted to at least 300K. In addition, we found that quantum mobility was independent of direction suggesting that the mechanism responsible is dominated by short-range, large q scattering. Both transport and quantum, mobility were reduced when donor layer correlations were removed using the process of bias cooling. Quantum mobility was more sensitive to this process although excess donors in the doping layer also affected values at high carrier densities. Applying Matthiessen's rule to both correlated and uncorrelated transport mobility data, strongly suggested that remote ionised impurity scattering was consistent with theory for samples with a 5nm spacer, but that an additional mechanism, as mentioned above, must exist in the samples with a 2.5nm spacer. Variable temperature studies further revealed that at low carrier densities, weak localisation was present, with strong, temperature dependent, activated transport also apparent at higher depletion. At high carrier densities in the thinnest spacer samples (2.5nm), a transport mobility peak evolved with decreasing temperature. The mechanism responsible was undetermined, but it was reminiscent of weak localisation-like behaviour. (author)

Multiscaling Dynamics of Impurity Transport in Drift-Wave Turbulence

International Nuclear Information System (INIS)

Futatani, S.; Benkadda, S.; Nakamura, Y.; Kondo, K.

2008-01-01

Intermittency effects and the associated multiscaling spectrum of exponents are investigated for impurities advection in tokamak edge plasmas. The two-dimensional Hasagawa-Wakatani model of resistive drift-wave turbulence is used as a paradigm to describe edge tokamak turbulence. Impurities are considered as a passive scalar advected by the plasma turbulent flow. The use of the extended self-similarity technique shows that the structure function relative scaling exponent of impurity density and vorticity follows the She-Leveque model. This confirms the intermittent character of the impurities advection in the turbulent plasma flow and suggests that impurities are advected by vorticity filaments

Toroidal asymmetries in divertor impurity influxes in NSTX

Directory of Open Access Journals (Sweden)

F. Scotti

2017-08-01

Full Text Available Toroidal asymmetries in divertor carbon and lithium influxes were observed in NSTX, due to toroidal differences in surface composition, tile leading edges, externally-applied three-dimensional (3D fields and toroidally-localized edge plasma modifications due to radio frequency heating. Understanding toroidal asymmetries in impurity influxes is critical for the evaluation of total impurity sources, often inferred from measurements with a limited toroidal coverage. The toroidally-asymmetric lithium deposition induced asymmetries in divertor lithium influxes. Enhanced impurity influxes at the leading edge of divertor tiles were the main cause of carbon toroidal asymmetries and were enhanced during edge localized modes. Externally-applied 3D fields led to strike point splitting and helical lobes observed in divertor impurity emission, but marginal changes to the toroidally-averaged impurity influxes. Power coupled to the scrape-off layer SOL plasma during radio frequency (RF heating of H-mode discharges enhanced impurity influxes along the non-axisymmetric divertor footprint of flux tubes connecting to plasma in front of the RF antenna.

Assessment of Embrittlement of VHTR Structural Alloys in Impure Helium Environments

Energy Technology Data Exchange (ETDEWEB)

Crone, Wendy; Cao, Guoping; Sridhara, Kumar

2013-05-31

The helium coolant in high-temperature reactors inevitably contains low levels of impurities during steady-state operation, primarily consisting of small amounts of H{sub 2}, H{sub 2}O, CH{sub 4}, CO, CO{sub 2}, and N{sub 2} from a variety of sources in the reactor circuit. These impurities are problematic because they can cause significant long-term corrosion in the structural alloys used in the heat exchangers at elevated temperatures. Currently, the primary candidate materials for intermediate heat exchangers are Alloy 617, Haynes 230, Alloy 800H, and Hastelloy X. This project will evaluate the role of impurities in helium coolant on the stress-assisted grain boundary oxidation and creep crack growth in candidate alloys at elevated temperatures. The project team will: • Evaluate stress-assisted grain boundary oxidation and creep crack initiation and crack growth in the temperature range of 500-850°C in a prototypical helium environment. • Evaluate the effects of oxygen partial pressure on stress-assisted grain boundary oxidation and creep crack growth in impure helium at 500°C, 700°C, and 850°C respectively. • Characterize the microstructure of candidate alloys after long-term exposure to an impure helium environment in order to understand the correlation between stress-assisted grain boundary oxidation, creep crack growth, material composition, and impurities in the helium coolant. • Evaluate grain boundary engineering as a method to mitigate stress-assisted grain boundary oxidation and creep crack growth of candidate alloys in impure helium. The maximum primary helium coolant temperature in the high-temperature reactor is expected to be 850-1,000°C.Corrosion may involve oxidation, carburization, or decarburization mechanisms depending on the temperature, oxygen partial pressure, carbon activity, and alloy composition. These corrosion reactions can substantially affect long-term mechanical properties such as crack- growth rate and fracture

Application of uranium impurity data for material characterization in nuclear safeguards

International Nuclear Information System (INIS)

Penkin, M.V.; Boulyga, S.F.; Fischer, D.M.

2016-01-01

Samples of materials involved in the conversion of uranium into nuclear-grade products are collected to support the verification of States' declarations and to look for indications of possible undeclared materials and activities. Samples are analysed by several laboratories to determine concentrations of about sixty impurities; the data consistency is addressed through the unified reporting requirements, the use of common reference materials, and via inter-laboratory comparisons. The impurity analysis results, along with other essential parameters, are interpreted to judge sample conformity to the relevant specifications, to evaluate the facility design information, to assess material provenance and intended use. (author)

Authoring and Enactment of Mobile Pyramid-Based Collaborative Learning Activities

Science.gov (United States)

Manathunga, Kalpani; Hernández-Leo, Davinia

2018-01-01

Collaborative learning flow patterns (CLFPs) formulate best practices for the orchestration of activity sequences and collaboration mechanisms that can elicit fruitful social interactions. Mobile technology features offer opportunities to support interaction mediation and content accessibility. However, existing mobile collaborative learning…

Impurities and conductivity in a D-wave superconductor

International Nuclear Information System (INIS)

Balatsky, A.V.

1994-01-01

Impurity scattering in the unitary limit produces low energy quasiparticles with anisotropic spectrum in a two-dimensional d-wave superconductor. The authors describe a new quasi-one-dimensional limit of the quasiparticle scattering, which might occur in a superconductor with short coherence length and with finite impurity potential range. The dc conductivity in a d-wave superconductor is predicted to be proportional to the normal state scattering rate and is impurity-dependent. They show that quasi-one-dimensional regime might occur in high-T c superconductors with Zn impurities at low temperatures T approx-lt 10 K

On impurity handling in high performance stellarator/heliotron plasmas

International Nuclear Information System (INIS)

Burhenn, R.; Feng, Y.; Ida, K.

2008-10-01

The Large Helical Device (LHD) and Wendelstein 7-X (W7-X, under construction) are experiments specially designed to demonstrate long pulse (quasi steady-state) operation, which is an intrinsic property of Stellarators and Heliotrons. Significant progress was made in establishment of high performance plasmas. A crucial point is the increasing impurity confinement towards high density as observed at several machines (TJ-II, W7-AS, LHD) which can lead to impurity accumulation and early pulse termination by radiation collapse at high density. In addition, theoretical predictions for non-axisymmetric configurations prognosticate the absence of impurity screening by ion temperature gradients in standard ion root plasmas. Nevertheless, scenarios were found where impurity accumulation was successfully avoided in LHD and/or W7-AS by the onset of drag forces in the high density and low temperature scrape-off-layer, the generation of magnetic islands at the plasma boundary and to a certain degree also by ELMs, flushing out impurities and reducing the net-impurity influx into the core. Additionally, a reduction of impurity core confinement was observed in the W7-AS High Density H-mode (HDH) regime and by application of sufficient ECRH heating power. The exploration of such purification mechanisms is a demanding task for successful steady-state operation. The impurity transport at the plasma edge/SOL was identified to play a major role for the global impurity behaviour in addition to the core confinement. (author)

Striped morphologies induced by magnetic impurities in d-wave superconductors

Science.gov (United States)

Zuo, Xian-Jun

2011-05-01

We study striped morphologies induced by magnetic impurities in d-wave superconductors (DSCs) near optimal doping by self-consistently solving the Bogoliubov-de Gennes equations based on the t - t‧ - U - V model. For the single-impurity case, it is found that the stable ground state is a modulated checkerboard pattern. For the two-impurity case, the stripe-like structures in order parameters are induced due to the impurity-pinning effect. The modulations of DSC and charge orders share the same period of four lattice constants (4 a), which is half the period of modulations in the coexisting spin order. Interestingly, when three or more impurities are inserted, the impurities could induce more complex striped morphologies due to quantum interference. Further experiments of magnetic impurity substitution in DSCs are expected to check these results.

Monte Carlo method for magnetic impurities in metals

Science.gov (United States)

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.

Determination of impurities and degradation products from veterinary medicinal products by HPLC method

Directory of Open Access Journals (Sweden)

Elena Gabriela Oltean

2014-06-01

Full Text Available The organic or inorganic impurities in the veterinary medicinal product can derive from starting materials, manufacturing process, incomplete purification, inappropriate storage. The acceptable levels of impurities in pharmaceuticals are estimated by comparison with standard solutions, according to the appropriate monographs. Forced degradation studies determine the stability of the method of dosage for the active compounds and for the entire finished product under excessive accelerated degradation conditions. They also provide information on degradation pathways and selectivity of analytical methods applied. The information provided by the degradation studies on the active compound and finished pharmaceutical product should demonstrate the specificity of the analytical method regarding impurities. Forced degradation studies should demonstrate that the impurities and degradation products generated do not interfere with the active compound. The current forced degradation methods consist of acid hydrolysis, basic hydrolysis, oxidation, exposure of the medicinal product to temperature and light. HPLC methods are an integral analytical instrument for the analysis of the medicinal product. The HPLC method should be able to separate, detect and quantify various specific degradation products that can appear after manufacture or storage of the medicinal product, as well as new elements appearing after synthesis. FDA and ICH guidelines recommend the enclosure of the results, including the chromatograms specific to the forced degradation-subjected medicinal product, in the documentation for marketing authorization. Using HPLC methods in forced degradation studies on medicinal products provides relevant information on the method of determination for the formulation of the medicinal product, synthesis product, packaging methods and storage.

Multisubband electron mobility in a parabolic quantum well structure under the influence of an applied electric field

International Nuclear Information System (INIS)

Sahoo, N.; Sahu, T.

2014-01-01

We study the multisubband electron mobility in a barrier delta doped Al x Ga 1−x As parabolic quantum well structure under the influence of an applied electric field perpendicular to the interface plane. We consider the alloy fraction x = 0.3 for barriers and vary x from 0.0 to 0.1 for the parabolic well. Electrons diffuse into the well and confine within the triangular like potentials near the interfaces due to Coulomb interaction with ionized donors. The parabolic structure potential, being opposite in nature, partly compensates the Coulomb potential. The external electric field further amends the potential structure leading to an asymmetric potential profile. Accordingly the energy levels, wave functions and occupation of subbands change. We calculate low temperature electron mobility as a function of the electric field and show that when two subbands are occupied, the mobility is mostly dominated by ionised impurity scattering mediated by intersubband effects. As the field increases transition from double subband to single subband occupancy occurs. A sudden enhancement in mobility is obtained due to curtailment of intersubband effects. Thereafter the mobility is governed by both impurity and alloy disorder scatterings. Our analysis of mobility as a function of the electric field for different structural parameters shows interesting results. (semiconductor physics)

Impurity dependence of superconductivity in niobium

International Nuclear Information System (INIS)

Laa, C.

1984-04-01

Jump temperatures, the critical fields Hsubc and Hsubc 2 and specific heats were measured on niobium samples where the impurity content was systematically varied by loading with nitrogen. Quantities could thus be extrapolated to lattice perfection and absolute purity. Comparisons with theories were made and some parameters extracted. Agreement was found with Gorkov theory for small impurities. A new value of the Ginsburg-Landau parameter Ko was determined to be just above 1/sqrt2 which proves that niobium is an elementary Type II semiconductor. By comparisons with the BCS and the CLAC theory the values of the mean Fermi velocity, the London penetration depth, the BCS coherence length and the impurity parameter were extracted. (G.Q.)

Impurity-induced states in superconducting heterostructures

Science.gov (United States)

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.

Impurities in sugar cane and their influence on industrial processing evaluated by nuclear techniques

International Nuclear Information System (INIS)

Bacchi, M.A.; Fernandes, E.A.N.; Ferraz, E.S.B.

1990-01-01

During the cutting and loading operations, impurities, mainly soil, are added to sugar cane in amounts that can impair industrial processing due to excessive wear of metallic members and contamination of juice and bagasse. Mechanization of loading operation has showed a considerable enhancement of the impurity content, leading to the improvement of cane washing technology. Nevertheless, for a correct understanding of the problem and the process optimization, it is necessary and exact and fast quantification of these impurities as well as of its consequences. Nuclear techniques, in special neutron activation analysis, have been proved to be appropriate for estimating soil level in sugar cane, washing process efficiency and wearing of cases and moving parts. (author)

Interpretation of plasma impurity deposition probes. Analytic approximation

Science.gov (United States)

Stangeby, P. C.

1987-10-01

Insertion of a probe into the plasma induces a high speed flow of the hydrogenic plasma to the probe which, by friction, accelerates the impurity ions to velocities approaching the hydrogenic ion acoustic speed, i.e., higher than the impurity ion thermal speed. A simple analytic theory based on this effect provides a relation between impurity fluxes to the probe Γimp and the undisturbed impurity ion density nimp, with the hydrogenic temperature and density as input parameters. Probe size also influences the collection process and large probes are found to attract a higher flux density than small probes in the same plasma. The quantity actually measured, cimp, the impurity atom surface density (m-2) net-deposited on the probe, is related to Γimp and thus to nimp by taking into account the partial removal of deposited material caused by sputtering and the redeposition process.

Ligand mobility modulates immunological synapse formation and T cell activation.

Directory of Open Access Journals (Sweden)

Chih-Jung Hsu

Full Text Available T cell receptor (TCR engagement induces clustering and recruitment to the plasma membrane of many signaling molecules, including the protein tyrosine kinase zeta-chain associated protein of 70 kDa (ZAP70 and the adaptor SH2 domain-containing leukocyte protein of 76 kDa (SLP76. This molecular rearrangement results in formation of the immunological synapse (IS, a dynamic protein array that modulates T cell activation. The current study investigates the effects of apparent long-range ligand mobility on T cell signaling activity and IS formation. We formed stimulatory lipid bilayers on glass surfaces from binary lipid mixtures with varied composition, and characterized these surfaces with respect to diffusion coefficient and fluid connectivity. Stimulatory ligands coupled to these surfaces with similar density and orientation showed differences in their ability to activate T cells. On less mobile membranes, central supramolecular activation cluster (cSMAC formation was delayed and the overall accumulation of CD3ζ at the IS was reduced. Analysis of signaling microcluster (MC dynamics showed that ZAP70 MCs exhibited faster track velocity and longer trajectories as a function of increased ligand mobility, whereas movement of SLP76 MCs was relatively insensitive to this parameter. Actin retrograde flow was observed on all surfaces, but cell spreading and subsequent cytoskeletal contraction were more pronounced on mobile membranes. Finally, increased tyrosine phosphorylation and persistent elevation of intracellular Ca(2+ were observed in cells stimulated on fluid membranes. These results point to ligand mobility as an important parameter in modulating T cell responses.

Collective impurity effects in the Heisenberg triangular antiferromagnet

International Nuclear Information System (INIS)

Maryasin, V S; Zhitomirsky, M E

2015-01-01

We theoretically investigate the Heisenberg antiferromagnet on a triangular lattice doped with nonmagnetic impurities. Two nontrivial effects resulting from collective impurity behavior are predicted. The first one is related to presence of uncompensated magnetic moments localized near vacancies as revealed by the low-temperature Curie tail in the magnetic susceptibility. These moments exhibit an anomalous growth with the impurity concentration, which we attribute to the clustering mechanism. In an external magnetic field, impurities lead to an even more peculiar phenomenon lifting the classical ground-state degeneracy in favor of the conical state. We analytically demonstrate that vacancies spontaneously generate a positive biquadratic exchange, which is responsible for the above degeneracy lifting

On neoclassical impurity transport in stellarator geometry

International Nuclear Information System (INIS)

García-Regaña, J M; Kleiber, R; Beidler, C D; Turkin, Y; Maaßberg, H; Helander, P

2013-01-01

The impurity dynamics in stellarators has become an issue of moderate concern due to the inherent tendency of the impurities to accumulate in the core when the neoclassical ambipolar radial electric field points radially inwards (ion root regime). This accumulation can lead to collapse of the plasma due to radiative losses, and thus limit high performance plasma discharges in non-axisymmetric devices. A quantitative description of the neoclassical impurity transport is complicated by the breakdown of the assumption of small E × B drift and trapping due to the electrostatic potential variation on a flux surface Φ-tilde compared with those due to the magnetic field gradient. This work examines the impact of this potential variation on neoclassical impurity transport in the Large Helical Device heliotron. It shows that the neoclassical impurity transport can be strongly affected by Φ-tilde . The central numerical tool used is the δf particle in cell Monte Carlo code EUTERPE. The Φ-tilde used in the calculations is provided by the neoclassical code GSRAKE. The possibility of obtaining a more general Φ-tilde self-consistently with EUTERPE is also addressed and a preliminary calculation is presented. (paper)

Gradient high performance liquid chromatography method for simultaneous determination of ilaprazole and its related impurities in commercial tablets

Directory of Open Access Journals (Sweden)

Shang Wang

2015-04-01

Full Text Available A methodology (HPLC proposed in this paper for simultaneously quantitative determination of ilaprazole and its related impurities in commercial tablets was developed and validated. The chromatographic separation was carried out by gradient elution using an Agilent C8 column (4.6 mm × 250 mm, 5 μm which was maintained at 25 °C. The mobile phase composed of solvent A (methanol and solvent B (solution consisting 0.02 mmol/l monopotassium phosphate and 0.025 mmol/l sodium hydroxide was at a flow rate of 1.0 ml/min. The samples were detected and quantified at 237 nm using an ultraviolet absorbance detector. Calibration curves of all analytes from 0.5 to 3.5 μg/ml were good linearity (r ≥ 0.9990 and recovery was greater than 99.5% for each analyte. The lower limit of detection (LLOD and quantification (LOQ of this analytical method were 10 ng/ml and 25 ng/ml for all impurities, respectively. The stress studies indicated that the degradation products could not interfere with the detection of ilaprazole and its related impurities and the assay can thus be considered stability-indicating. The method precisions were in the range of 0.41–1.21 while the instrument precisions were in the range of 0.38–0.95 in terms of peak area RSD% for all impurities, respectively. This method is considered stability-indicating and is applicable for accurate and simultaneous measuring of the ilaprazole and its related impurities in commercial enteric-coated tablets.

Simulated impurity transport in LHD from MIST

Energy Technology Data Exchange (ETDEWEB)

Rice, J.E. [National Inst. for Fusion Science, Toki, Gifu (Japan)

1998-05-01

The impurity transport code MIST and atomic physics package LINES are used to calculate the time evolution of charge state density profiles, individual line emissivity profiles and total radiated power profiles for impurities in LHD plasmas. Three model LHD plasmas are considered; a high density, low temperature case, a low density, high temperature case and the initial LHD start-up plasma (500 kW ECH), using impurity transport coefficient profiles from Heliotron E. The elements oxygen, neon, scandium, iron, nickel and molybdenum are considered, both injected and in steady state. (author)

Scattering of waves by impurities in precompressed granular chains.

Science.gov (United States)

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.

Spin-1 two-impurity Kondo problem on a lattice

Science.gov (United States)

Allerdt, A.; Žitko, R.; Feiguin, A. E.

2018-01-01

We present an extensive study of the two-impurity Kondo problem for spin-1 adatoms on a square lattice using an exact canonical transformation to map the problem onto an effective one-dimensional system that can be numerically solved using the density matrix renormalization group method. We provide a simple intuitive picture and identify the different regimes, depending on the distance between the two impurities, Kondo coupling JK, longitudinal anisotropy D , and transverse anisotropy E . In the isotropic case, two impurities on opposite (the same) sublattices have a singlet (triplet) ground state. However, the energy difference between the triplet ground state and the singlet excited state is very small and we expect an effectively fourfold-degenerate ground state, i.e., two decoupled impurities. For large enough JK the impurities are practically uncorrelated forming two independent underscreened states with the conduction electrons, a clear nonperturbative effect. When the impurities are entangled in an RKKY-like state, Kondo correlations persist and the two effects coexist: the impurities are underscreened, and the dangling spin-1 /2 degrees of freedom are responsible for the interimpurity entanglement. We analyze the effects of magnetic anisotropy in the development of quasiclassical correlations.

Impurity doping: a novel strategy for controllable synthesis of functional lanthanide nanomaterials.

Science.gov (United States)

Chen, Daqin; Wang, Yuansheng

2013-06-07

Many technological nanomaterials are intentionally 'doped' by introducing appropriate amounts of foreign elements into hosts to impart electronic, magnetic and optical properties. In fact, impurity doping was recently found to have significant influence on nucleation and growth of many functional nanocrystals (NCs), and provide a fundamental approach to modify the crystallographic phase, size, morphology, and electronic configuration of nanomaterials. In this feature article, we provide an overview of the most recent progresses in doping-induced control of phase structures, sizes, shapes, as well as performances of functional nanomaterials for the first time. Two kinds of impurity doping strategies, including the homo-valence ion doping and hetero-valence ion doping, are discussed in detail. We lay emphases on impurity doping induced modifications of microstructures and optical properties of upconversion (UC) lanthanide (Ln(3+)) NCs, but do not limit to them. In addition, we also illustrate the control of Ln(3+) activator distribution in the core@shell architecture, which has recently provided scientists with new opportunities for designing and tuning the multi-color emissions of Ln(3+)-doped UC NCs. Finally, the challenges and future perspectives of this novel impurity doping strategy are pointed out.

Breatherlike impurity modes in discrete nonlinear lattices

DEFF Research Database (Denmark)

Hennig, D.; Rasmussen, Kim; Tsironis, G. P.

1995-01-01

We investigate the properties of a disordered generalized discrete nonlinear Schrodinger equation, containing both diagonal and nondiagonal nonlinear terms. The equation models a Linear host lattice doped with nonlinear impurities. We find different types of impurity states that form itinerant...

Light impurity transport in JET ILW L-mode plasmas

Science.gov (United States)

Bonanomi, N.; Mantica, P.; Giroud, C.; Angioni, C.; Manas, P.; Menmuir, S.; Contributors, JET

2018-03-01

A series of experimental observations of light impurity profiles was carried out in JET (Joint European Torus) ITER-like wall (ILW) L-mode plasmas in order to investigate their transport mechanisms. These discharges feature the presence of 3He, Be, C, N, Ne, whose profiles measured by active Charge Exchange diagnostics are compared with quasi-linear and non-linear gyro-kinetic simulations. The peaking of 3He density follows the electron density peaking, Be and Ne are also peaked, while the density profiles of C and N are flat in the mid plasma region. Gyro-kinetic simulations predict peaked density profiles for all the light impurities studied and at all the radial positions considered, and fail predicting the flat or hollow profiles observed for C and N at mid radius in our cases.

Quantitative determination of salbutamol sulfate impurities using achiral supercritical fluid chromatography.

Science.gov (United States)

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.

Incorporation, diffusion and segregation of impurities in polycrystalline silicon

Energy Technology Data Exchange (ETDEWEB)

Deville, J.P.; Soltani, M.L. (Universite Louis Pasteur, 67 - Strasbourg (France)); Quesada, J. (Laboratoire de Metallurgie-Chimie des Materiaux, E.N.S.A.I.S., 67 - Strasbourg (France))

1982-01-01

We studied by means of X-Ray photoelectron Spectroscopy the nature, distribution and, when possible, the chemical bond of impurities at the surface of polycrystalline silicon samples grown on a carbon ribbon. Besides main impurities (carbon and oxygen), always present at concentrations around their limit of solubility in silicon, metal impurities have been found: their nature varies from one sample to another. Their spatial distribution is not random: some are strictly confined at the surface (sodium), whereas others are in the superficial oxidized layer (calcium, magnesium) or localized at the oxide-bulk silicon interface (iron). Metal impurities are coming from the carbon ribbon and are incorporated to silicon during the growth process. It is not yet possible to give a model of diffusion processes of impurities since they are too numerous and interact one with the other. However oxygen seems to play a leading role in the spatial distribution of metal impurities.

Quantum one dimensional spin systems. Disorder and impurities

International Nuclear Information System (INIS)

Brunel, V.

1999-01-01

This thesis presents three studies that are respectively the spin-1 disordered chain, the non magnetic impurities in the spin-1/2 chain and the reaction-diffusion process. The spin-1 chain of weak disorder is performed by the Abelian bosonization and the renormalization group. This allows to take into account the competition between the disorder and the interactions and predicts the effects of various spin-1 anisotropy chain phases under many different disorders. A second work uses the non magnetic impurities as local probes of the correlations in the spin-1/2 chain. When the impurities are connected to the chain boundary, the author predicts a temperature dependence of the relaxation rate (1/T) of the nuclear spin impurities, different from the case of these impurities connected to the whole chain. The last work deals with one dimensional reaction-diffusion problem. The Jordan-Wigner transformation allows to consider a fermionic field theory that critical exponents follow from the renormalization group. (A.L.B.)

Impurity injection into tokamak plasmas by erosion probes

International Nuclear Information System (INIS)

Hildebrandt, D.; Bakos, J.S.; Buerger, G.; Paszti, F.; Petravich, G.

1987-08-01

Exposing special erosion probes into the edge plasma of MT-1 the impurities Li and Ti were released and contaminated the plasma. By the use of collector probes the torodial transport of these impurities were investigated. The results indicate a preferential impurity flow into codirection of the plasma current. However, the asymmetric component of this flow is much larger than expected from the toroidal drift correlated to the plasma current. (author)

Fractal growth in impurity-controlled solidification in lipid monolayers

DEFF Research Database (Denmark)

Fogedby, Hans C.; Sørensen, Erik Schwartz; Mouritsen, Ole G.

1987-01-01

A simple two-dimensional microscopic model is proposed to describe solidifcation processes in systems with impurities which are miscible only in the fluid phase. Computer simulation of the model shows that the resulting solids are fractal over a wide range of impurity concentrations and impurity...... diffusional constants. A fractal-forming mechanism is suggested for impurity-controlled solidification which is consistent with recent experimental observations of fractal growth of solid phospholipid domains in monolayers. The Journal of Chemical Physics is copyrighted by The American Institute of Physics....

Impurity effects in the electrothermal instability

International Nuclear Information System (INIS)

Tomimura, A.; Azevedo, M.T. de

1982-01-01

A 'impure' plasma model is proposed based on the homogeneous hydrogen plasma used in the theory formulated by Tomimura and Haines to explain the electrothermal instable mode growth with the wave vector perpendicular to the applied magnetic field. The impurities are introduced implicitly in the transport coefficients of the two-fluid model through a effective charge number Z sub(eff). (Author) [pt

Transport and re-deposition of limiter-released metal impurities

International Nuclear Information System (INIS)

Claasen, H.A.; Repp, H.

1983-01-01

The transport parallel B-vector and re-deposition of limiter- (or divertor-target-)released metal impurities in a given counter-streaming scrape-off layer plasma is studied analytically by using a kinetic approach. Electron impact ionization, Coulomb collisions with the hydrogen ions, and impurity ion acceleration in a pre-sheath electric field are accounted for. The friction and electric-field forces provide the driving forces for impurity re-cycling in front of the limiter. Both hydrogen ion sputtering and self-sputtering are included (the latter for impurity emission perpendicular to the limiter surface). The analytical formulas are numerically evaluated for the example of sputtered iron impurities, assuming a simple model for a scrape-off layer plasma in contact with a stainless-steel poloidal ring limiter. (author)

Transitions and excitations in a superfluid stream passing small impurities

KAUST Repository

Pinsker, Florian

2014-05-08

We analyze asymptotically and numerically the motion around a single impurity and a network of impurities inserted in a two-dimensional superfluid. The criticality for the breakdown of superfluidity is shown to occur when it becomes energetically favorable to create a doublet—the limiting case between a vortex pair and a rarefaction pulse on the surface of the impurity. Depending on the characteristics of the potential representing the impurity, different excitation scenarios are shown to exist for a single impurity as well as for a lattice of impurities. Depending on the lattice characteristics it is shown that several regimes are possible: dissipationless flow, excitations emitted by the lattice boundary, excitations created in the bulk, and the formation of large-scale structures.

Transitions and excitations in a superfluid stream passing small impurities

KAUST Repository

Pinsker, Florian; Berloff, Natalia G.

2014-01-01

We analyze asymptotically and numerically the motion around a single impurity and a network of impurities inserted in a two-dimensional superfluid. The criticality for the breakdown of superfluidity is shown to occur when it becomes energetically favorable to create a doublet—the limiting case between a vortex pair and a rarefaction pulse on the surface of the impurity. Depending on the characteristics of the potential representing the impurity, different excitation scenarios are shown to exist for a single impurity as well as for a lattice of impurities. Depending on the lattice characteristics it is shown that several regimes are possible: dissipationless flow, excitations emitted by the lattice boundary, excitations created in the bulk, and the formation of large-scale structures.

The origin of metal impurities in DIVA

International Nuclear Information System (INIS)

Ohasa, Kazumi; Sengoku, Seio; Maeda, Hikosuke; Ohtsuka, Hideo; Yamamoto, Shin

1978-10-01

The origin of metal impurities in DIVA (JFT-2a Tokamak) has been studied experimentally. Three processes of metal impurity release from the first wall were identified; i.e. ion sputtering, evaporation, and arcing. Among of these, ion sputtering is the predominant process in the quiet phase of the discharge, which is characterized by no spikes in the loop voltage and no localized heat flux concentrations on the first wall. ''Cones'' formation due to the sputtering is observed on the gold protection plate (guard limiter) exposed to about 10,000 discharges by scanning electron micrograph. In the SEM photographs, the spacial distribution of cones on the shell surface due to the ion sputtering coincides with the spacial distribution of intensity of Au-I line radiation. Gold is the dominant metal impurity in DIVA. The honeycomb structure can decrease release of the metal impurity. (author)

Embodied Computation: An Active-Learning Approach to Mobile Robotics Education

Science.gov (United States)

Riek, L. D.

2013-01-01

This paper describes a newly designed upper-level undergraduate and graduate course, Autonomous Mobile Robots. The course employs active, cooperative, problem-based learning and is grounded in the fundamental computational problems in mobile robotics defined by Dudek and Jenkin. Students receive a broad survey of robotics through lectures, weekly…

Impurity dynamics in stellarator W7-AS plasmas

International Nuclear Information System (INIS)

Igitkhanov, Yuri; Beidler, Craig D.; Burhenn, Reiner; Polunovsky, Eduard; Yamazaki, Kozo

2006-01-01

Numerical efforts to understand the neoclassical transport of impurities in stellarator plasmas have been undertaken. The new code solves the radial continuity equations for each ionization stage of the impurity ions for given background plasma profiles and magnetic configuration. An analytic description of the neoclassical transport coefficients based on numerical results from the DKES (Drift Kinetic Equation Solver) code and monoenergetic Monte-Carlo calculation (C.D. Beidler et al., EPS 1994), is here applied for impurity transport coefficients. The transition between the different charge states due to the ionization and recombination in balance equation is described by using the ADAS (Atomic Data and Analysis Structure) database. The impurity behavior in some typical discharges from W7-AS with moderate (NC) and improved energy confinement (HDH) has been considered. It is shown that the spatial distribution results from the competition between the radial electric field and the thermal force (which together produce a convective flux), and the diffusive term, which flattens the radial impurity distribution. The impurity ions are localized at the radial position where the convective flux goes through zero. It is also shown that for typical stellarator discharges there is no pronounced temperature screening effect as in tokamak plasmas. (author)

DETERMINATION OF RELATED IMPURITIES IN THE ANILOCAINE SUBSTANCE BY HPLC METHOD

Directory of Open Access Journals (Sweden)

D. R. Sabirzyanov

2017-01-01

Full Text Available Anilocaine is a local anesthetic from the group of substituted amides, synthesized in the Perm State Pharmaceutical Academy. Anilocaine shows high surface anesthetic, infiltration and conduction anesthesia and shows the high efficiency in the various fields of medical practice. The quality of produced medicines depends on the quality of pharmaceutical substances. The purity is one of the most important parameters of the quality of pharmaceutical substances. The aim of this work was the development and validation of methods for identification of specific impurities in the substance of anilocaine by high-performance liquid chromatography (HPLC. Materials and methods. Studies were performed on liquid chromatography LC-20 Prominence (Shimadzu, Japan equipped with a diode-array detector (SPD-M20A. Chromatographic column was Zorbax SB-C18 (4.6 mm × 250 mm, 5 μm. Validation assessment of the developed method conducted in accordance with the requirements of FP XIII and international requirementsICH (International Conference on Harmonization. Results and discussion. An experiment on the selection of the conditions of chromatographically showed that optimal separation of anilocaine and possible impurities (identified and unidentified by the method of reversed-phase HPLC is observed in isocratic mode, using an eluent based on phosphate buffer pH 3 and acetonitrile. The flow rate of mobile phase is 1 ml/min; wavelength detection is 210 nm. Time check chromatogram is 20 minutes. Conclusion. The method for the quantitative determination of impurities in the substance of anilocaine by high-performance liquid chromatography was developed as the result of the research. The validation procedure of the analytical methods established its specificity, linearity, precision and accuracy. This method is included in the project monograph on substance of anilocaine.

Influence of the impurities on the depth of penetration with carbon steel weldings

Directory of Open Access Journals (Sweden)

O. Savytsky

2014-04-01

Full Text Available In this paper the results of the research about the influence of the impurities on the depth of penetration with carbon steels weldings of different chemical composition are presented. These data suggest that presence of those impurities, such as sulphure and oxygen, in the steel, increases the depth of penetration to 1,3 - 1,5 times compared to welding refined steels. Applying activating fluxes for welding high tensile steels, provides an increase in the depth of penetration of 2 - 3 times.

A validated stability-indicating LC method for the separation of enantiomer and potential impurities of Linezolid using polar organic mode.

Science.gov (United States)

Satyanarayana Raju, T; Vishweshwari Kutty, O; Ganesh, V; Yadagiri Swamy, P

2012-08-01

Although a number of methods are available for evaluating Linezolid and its possible impurities, a common method for separation if its potential impurities, degradants and enantiomer in a single method with good efficiency remain unavailable. With the objective of developing an advanced method with shorter runtimes, a simple, precise, accurate stability-indicating LC method was developed for the determination of purity of Linezolid drug substance and drug products in bulk samples and pharmaceutical dosage forms in the presence of its impurities and degradation products. This method is capable of separating all the related substances of Linezolid along with the chiral impurity. This method can also be used for the estimation of assay of Linezolid in drug substance as well as in drug product. The method was developed using Chiralpak IA (250 mm×4.6 mm, 5 μm) column. A mixture of acetonitrile, ethanol, n-butyl amine and trifluoro acetic acid in 96:4:0.10:0.16 (v/v/v/v) ratio was used as a mobile phase. The eluted compounds were monitored at 254 nm. Linezolid was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal and photolytic degradation. The degradation products were well resolved from main peak and its impurities, proving the stability-indicating power of the method. The developed method was validated as per International Conference on Harmonization (ICH) guidelines with respect to specificity, limit of detection, limit of quantification, precision, linearity, accuracy, robustness and system suitability.

Impurity and trace tritium transport in tokamak edge turbulence

DEFF Research Database (Denmark)

Naulin, V.

2005-01-01

The turbulent transport of impurity or minority species, as for example tritium, is investigated in drift-Alfven edge turbulence. The full effects of perpendicular and parallel convection are kept for the impurity species. The impurity density develops a granular structure with steep gradients...... and locally exceeds its initial values due to the compressibility of the flow. An approximate decomposition of the impurity flux into a diffusive part and an effective convective part (characterized by a pinch velocity) is performed and a net inward pinch effect is recovered. The pinch velocity is explained...

EUV impurity study of the Alcator tokamak

International Nuclear Information System (INIS)

Terry, J.L.; Chen, K.I.; Moos, H.W.; Marmar, E.S.

1977-06-01

The intensity of resonance line radiation from oxygen, nitrogen, carbon and molybdenum impurities has been measured in the high field (80 kG), high density (6 x 10 14 cm -3 ) discharges of the Alcator tokamak, using a 0.4 m normal incidence monochromator (300 to 1300 A) with its line of sight fixed along a major radius. The total light impurity concentrations were 2 x 10 -3 , 7 x 10 -4 , and 3 x 10 -3 at central electron densities of 4.5 x 10 13 cm -3 (burnout), 4.0 x 10 13 (low density plateau) and 6.0 x 10 14 (high density plateau). Both a simple model and a computer code which included Pfirsch-Schluter impurity diffusion were used to estimate oxygen influxes of 1.6 x 10 13 cm -2 sec -1 and 1.5 x 10 14 cm -2 sec -1 at the plasma edge in the low and high density emission plateaus. The resulting values of Z/sub eff/, including the contributions due to both the light impurities and molybdenum, were close to one. The power lost through the impurity line radiation accounted for approximately equal to 7 percent of the total ohmic input power at high densities

Transport of impurities during H-mode pulses in JET

International Nuclear Information System (INIS)

Giannella, R.; Gottardi, N.; Mompean, F.; Mori, H.; Pasini, D.; Stork, D.; Barnsley, R.; Hawkes, N.C.; Lawson, K.

1990-01-01

The transport of impurities during the H-mode is very different from that observed in the other regimes. This is clearly evident in the quiescent discharges where the confinement time of impurities τ I are measured in all the quiescent H-mode discharges in spite of the variety of impurity behavior observed corresponding to different plasma parameters and operating scenarios. The condition of the machine has an influence on the role played by the various impurities, but this does not seem to affect the flow patterns of these ions substantially. In particular oxygen, which was often detected as the dominant radiator, can be reduced to a negligible fraction by He conditioning of the carbon X-point tiles or limiters or by evaporating beryllium in the vacuum vessel. Nevertheless the behaviour of the residual impurities in otherwise similar discharges remains substantially unchanged. The transport patterns appear in fact to be affected by the plasma parameters and their profiles. In particular, two extreme transport regimes are presented in the following. These discharges have been modelled with the aid of a recently developed fully time-dependent impurity transport code using heuristic profiles for the impurity diffusion D and the convection velocity v. (author) 4 refs., 5 figs

Determination of Degradation Products of Cyclobenzaprine Hydrochloride, Lidocaine and Piroxicam in a Semi-Topical Formulation: MS-MS Confirmation of Unknown Impurities.

Science.gov (United States)

Cioroiu, Bogdan Ionel; Grigoriu, Ioana Cezara; Cioroiu, Mona Elisabeta; Niculaua, Marius; Lupuleasa, Roxana; Lazar, Mihai Ioan

2016-07-01

Association of cyclobenzaprine hydrochloride, piroxicam and lidocaine in a topical formulation is one of the newest innovations in the pharmaceutical formulary field. In this study, a reversed-phase liquid chromatographic method was developed for the establishment of the impurities of cyclobenzaprine hydrochloride, lidocaine and piroxicam in the semisolid topical formulation. In this study, we not only determined 2,6-dimethylaniline, 2-pyrydilamine but also specified impurities of cyclobenzaprine hydrochloride (dibenzosuberenone, amitriptyline, carbinole, cyclobenzaprine N-oxide and anthrachinone). The target compounds were determined using a mobile phase that consisted of a mixture of phosphate buffer (0.025 M; pH 6.2)-acetonitrile-methanol (60 : 13 : 27, v/v/v). A minimum of three supplementary possible degradation products were determined. Using mass spectrometry, the unspecified impurities were identified and the use of correlation matrices permitted the association with the possible source compounds. The chromatographic conditions were qualified and validated according to ICH guideline requirements to confirm specificity, linearity, accuracy and precision. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Moving discrete breathers in a Klein-Gordon chain with an impurity

International Nuclear Information System (INIS)

Cuevas, J; Palmero, F; Archilla, J F R; Romero, F R

2002-01-01

We analyse the influence of an impurity in the evolution of moving discrete breathers in a Klein-Gordon chain with non-weak nonlinearity. Three different types of behaviour can be observed when moving breathers interact with the impurity: they pass through the impurity continuing their direction of movement; they are reflected by the impurity; they are trapped by the impurity, giving rise to chaotic breathers, as their Fourier power spectra show. Resonance with a breather centred at the impurity site is conjectured to be a necessary condition for the appearance of the trapping phenomenon. This paper establishes a difference between the resonance condition of the non-weak nonlinearity approach and the resonance condition with the linear impurity mode in the case of weak nonlinearity

Characterization of impurities in biogas before and after upgrading to vehicle fuel

Energy Technology Data Exchange (ETDEWEB)

Arrhenius, Karine; Johansson, Ulrika [SP Technical Research Institute of Sweden, Boraas (Sweden)

2012-01-15

Biogases produced by digesting organic wastes, residual sludge from waste water treatment, energy crops,byproducts from industry or in landfills contain impurities which can be harmful for components that will be in contact with the biogas during its utilization. In this project, the impurities present in biogases have been mapped out depending upon which feedstock is digested. P-cymene och D-limonene, two terpenes, have been found to be characteristics for biogases produced from the digestion of waste including household wastes while an 'oil' fraction containing alkanes with 9 to 13 carbon atoms is characteristic for biogases produced at waste water treatment plants. Ketones and sulfur compounds are found in biogases produced from the digestion of food industry wastes or energy crops. It was not possible to characterize impurities in biogases produced in farm plants digesting manure because not enough samples were analyzed from these plants. In order to understand the relation between the feedstock and the impurities present in the biogas, an extensive study on feedstock characterization must be conducted. One question to be answered is if these impurities only originate from the volatilization from the feedstock and in this case, why only these specific compounds are found at significant concentrations. In this study we have also studied how effective purification/upgrading techniques are to remove impurities that have been identified in biogases. En general comment is that the upgraded gas still contains a part of the characteristic impurities which have been identified for each feedstock at different levels of concentration depending on which technique has been used. The results show that activated carbon filters are more or less effective. Some of them can remove more than 90 % of the impurities while others remove less that 10 %. Results show also that the amine scrubber have very moderate effects on the impurities composition. In that case, the

Behaviour of impurities during the H-mode in JET

International Nuclear Information System (INIS)

Gianella, R.; Behringer, K.; Denne, B.; Gottardi, N.; Hellermann, M. von; Morgan, P.D.; Pasini, D.; Stamp, M.F.

1989-01-01

In additionally-heated tokamak discharges, the H-mode phases are reported to display, together with a better energy confinement, a longer global containment time for particles. In particular, steep gradients of electron density and temperature are sustained in the outer region of the plasma column. This enhanced performance is observed especially in discharges in which the activity of edge localized modes (ELMs) is low or absent. High confinement and accumulation of metallic impurities, which quickly give raise to terminal disruptions have been described under similar conditions. In JET H-modes very long impurity confinement times are also observed. However the experimental condition is somewhat more favourable since quiescent H-modes are obtained lasting much longer than the energy confinement times and the radiation from metals is generally negligible. The dominant impurities are normally carbon and oxygen, the latter generally accounting for half or more of the power radiated from the bulk plasma. During the X-point operation the effective influx of carbon into the discharge, which is normally in close correlation with that of deuterium, is substantially reduced while the influx of oxygen, whose production mechanisms is believed to be of a chemical nature, does not show significant variations. (author) 5 refs., 4 figs

Development and validation of an ICP-MS method for the determination of elemental impurities in TP-6076 active pharmaceutical ingredient (API) according to USP 〈232〉/〈233〉.

Science.gov (United States)

Chahrour, Osama; Malone, John; Collins, Mark; Salmon, Vrushali; Greenan, Catherine; Bombardier, Amy; Ma, Zhongze; Dunwoody, Nick

2017-10-25

The new guidelines of the United States pharmacopeia (USP), European pharmacopeia (EP) and international conference on harmonization (ICH) regulating elemental impurities limits in pharmaceuticals signify the end of unspecific analysis of metals as outlined in USP 〈231〉. The new guidelines specify both daily doses and concentration/limits of elemental impurities in pharmaceutical final products, active pharmaceutical ingredients (API) and excipients. In chapter USP 〈233〉 method implementation, validation and quality control during the analytical process are described. We herein report the use of a stabilising matrix that overcomes low spike recovery problem encountered with Os and allows the determination of all USP required elemental impurities (As, Cd, Hg, Pb, V, Cr, Ni, Mo, Cu, Pt, Pd, Ru, Rh, Os and Ir) in a single analysis. The matrix was used in the validation of a method to determine elemental impurities in TP-6076 active pharmaceutical ingredient (API) by ICP-MS according to the procedures defined in USP〈233〉 and to GMP requirements. This validation will support the regulatory submission of TP-6076 which is a novel tetracycline analogue effective against the most urgent multidrug-resistant gram-negative bacteria. Evaluation of TP-6076 in IND-enabling toxicology studies has led to the initiation of a phase 1 clinical trial. Copyright © 2017 Elsevier B.V. All rights reserved.

Glycolic acid physical properties and impurities assessment

Energy Technology Data Exchange (ETDEWEB)

Lambert, D. P. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Pickenheim, B. R. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Hay, M. S. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); BIBLER, N. E. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2017-08-09

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, 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.

Complexity of Quantum Impurity Problems

Science.gov (United States)

Bravyi, Sergey; Gosset, David

2017-12-01

We give a quasi-polynomial time classical algorithm for estimating the ground state energy and for computing low energy states of quantum impurity models. Such models describe a bath of free fermions coupled to a small interacting subsystem called an impurity. The full system consists of n fermionic modes and has a Hamiltonian {H=H_0+H_{imp}}, where H 0 is quadratic in creation-annihilation operators and H imp is an arbitrary Hamiltonian acting on a subset of O(1) modes. We show that the ground energy of H can be approximated with an additive error {2^{-b}} in time {n^3 \\exp{[O(b^3)]}}. Our algorithm also finds a low energy state that achieves this approximation. The low energy state is represented as a superposition of {\\exp{[O(b^3)]}} fermionic Gaussian states. To arrive at this result we prove several theorems concerning exact ground states of impurity models. In particular, we show that eigenvalues of the ground state covariance matrix decay exponentially with the exponent depending very mildly on the spectral gap of H 0. A key ingredient of our proof is Zolotarev's rational approximation to the {√{x}} function. We anticipate that our algorithms may be used in hybrid quantum-classical simulations of strongly correlated materials based on dynamical mean field theory. We implemented a simplified practical version of our algorithm and benchmarked it using the single impurity Anderson model.

Impurity and particle control for INTOR

International Nuclear Information System (INIS)

Post, D.

1985-02-01

The INTOR impurity control system studies have been focused on the development of an impurity control system which would be able to provide the necessary heat removal and He pumping while satisfying the requirements for (1) minimum plasma contamination by impurities, (2) reasonable component lifetime (approx. 1 year), and (3) minimum size and cost. The major systems examined were poloidal divertors and pumped limiters. The poloidal divertor was chosen as the reference option since it offered the possibility of low sputtering rates due to the formation of a cool, dense plasma near the collector plates. Estimates of the sputtering rates associated with pumped limiters indicated that they would be too high for a reasonable system. Development of an engineering design concept was done for both the poloidal divertor and the pumped limiter

A Motivational Physical Activity Intervention for Improving Mobility in Older Korean Americans.

Science.gov (United States)

Yeom, Hye-A; Fleury, Julie

2014-07-01

There has been limited empirical support for interventions designed to promote physical activity targeting mobility in racially diverse older adults. This study aims to examine the effects of a Motivational Physical Activity Intervention (MPAI) on social resource, behavioral change process, physical activity, and mobility variables in sedentary older Korean Americans. A quasi-experimental, repeated-measure, pre- and post-tests design was used. Sixty-four community-dwelling, sedentary older Korean Americans (n = 33 for MPAI group, n = 31 for Attention Control group) participated in the study. There were significant improvements in social resources, including social support from family and friends; behavioral change process variables, including self-efficacy; motivational appraisal; and self-regulation for physical activity. There were significant intervention effects on physical activity, walking endurance, and flexibility. The MPAI is supported as improving mobility and physical activity, as well as increasing motivation for physical activity in older Korean Americans. © The Author(s) 2013.

Scaling laws for trace impurity confinement: a variational approach

International Nuclear Information System (INIS)

Thyagaraja, A.; Haas, F.A.

1990-01-01

A variational approach is outlined for the deduction of impurity confinement scaling laws. Given the forms of the diffusive and convective components to the impurity particle flux, we present a variational principle for the impurity confinement time in terms of the diffusion time scale and the convection parameter, which is a non-dimensional measure of the size of the convective flux relative to the diffusive flux. These results are very general and apply irrespective of whether the transport fluxes are of theoretical or empirical origin. The impurity confinement time scales exponentially with the convection parameter in cases of practical interest. (orig.)

Zirconium analysis. Impurities determination by spark mass specrometry

International Nuclear Information System (INIS)

Anon.

Determination of impurities in zirconium, suitable for atomic content greater than 10 -8 but particularly adapted for low contents. The method is quantitative only if a reference sample is available (metallic impurities) [fr

First-principles calculations of impurity diffusion coefficients in dilute Mg alloys using the 8-frequency model

International Nuclear Information System (INIS)

Ganeshan, S.; Hector, L.G.; Liu, Z.-K.

2011-01-01

Research highlights: → Implemented the eight frequency model for impurity diffusion in hexagonal metals. → Model inputs were energetics/vibrational properties from first princples. → Predicted diffusion coefficients for Al, Ca, Zn and Sn impurity diffusion in Mg. → Successful prediction of partial correlation factors and jump frequencies. → Good agreement between calculated and experimental results. - Abstract: Diffusion in dilute Mg-X alloys, where X denotes Al, Zn, Sn and Ca impurities, was investigated with first-principles density functional theory in the local density approximation. Impurity diffusion coefficients were computed as a function of temperature using the 8-frequency model which provided the relevant impurity and solvent (Mg) jump frequencies and correlation factors. Minimum energy pathways for impurity diffusion and associated saddle point structures were computed with the climbing image nudged elastic band method. Vibrational properties were obtained with the supercell (direct) method for lattice dynamics. Calculated diffusion coefficients were compared with available experimental data. For diffusion between basal planes, we find D Mg-Ca > D Mg-Zn > D Mg-Sn > D Mg-Al, where D is the diffusion coefficient. For diffusion within a basal plane, the same trend holds except that D Mg-Zn overlaps with D Mg-Al at high temperatures and D Mg-Sn at low temperatures. These trends were explored with charge density contours in selected planes of each Mg-X alloy, the variation of the activation energy for diffusion with the atomic radius of each impurity and the electronic density of states. The theoretical methodology developed herein can be applied to impurity diffusion in other hexagonal materials.

Persuasive Technology in Mobile Applications Promoting Physical Activity: a Systematic Review.

Science.gov (United States)

Matthews, John; Win, Khin Than; Oinas-Kukkonen, Harri; Freeman, Mark

2016-03-01

Persuasive technology in mobile applications can be used to influence the behaviour of users. A framework known as the Persuasive Systems Design model has been developed for designing and evaluating systems that influence the attitudes or behaviours of users. This paper reviews the current state of mobile applications for health behavioural change with an emphasis on applications that promote physical activity. The inbuilt persuasive features of mobile applications were evaluated using the Persuasive Systems Design model. A database search was conducted to identify relevant articles. Articles were then reviewed using the Persuasive Systems Design model as a framework for analysis. Primary task support, dialogue support, and social support were found to be moderately represented in the selected articles. However, system credibility support was found to have only low levels of representation as a persuasive systems design feature in mobile applications for supporting physical activity. To ensure that available mobile technology resources are best used to improve the wellbeing of people, it is important that the design principles that influence the effectiveness of persuasive technology be understood.

Isospin impurity and super-allowed β transitions

International Nuclear Information System (INIS)

Sagawa, H.; Van Giai Nguyen; Suzuki, T.

1999-01-01

We study the effect of isospin impurity on the super-allowed Fermi β decay using microscopic HF and RPA (or TDA) model taking into account CSB and CIB interactions. It is found that the isospin impurity of N = Z nuclei gives enhancement of the sum rule of Fermi transition probabilities. On the other hand, the super-allowed transitions between odd-odd J = 0 nuclei and even-even J = 0 nuclei are quenched because on the cancellation of the isospin impurity effects of mother and daughter nuclei. An implication of the calculated Fermi transition rate on the unitarity of Cabbibo-Kobayashi-Maskawa mixing matrix is also discussed. (authors)

Dynamics of impurities in the scrape-off layer

International Nuclear Information System (INIS)

Stangeby, P.C.; Commission of the European Communities, Abingdon

1988-01-01

Impurity modelling of the Scrape-Off Layer, SOL, is reviewed. Simple analytic models are sometimes adequate for relating central impurity levels to edge plasma conditions and for explaining the patterns of net erosion/deposition found on limiters. More sophisticated approaches, which are also necessary, are categorized and reviewed. A plea is made for the acquisition of a more comprehensive data base of edge plasma properties since reliable impurity modelling appears to be dependent on more extensive use of experimental input. (author)

Metal impurity fluxes and plasma-surface interactions in EXTRAP T2R

Science.gov (United States)

Bergsåker, H.; Menmuir, S.; Rachlew, E.; Brunsell, P. R.; Frassinetti, L.; Drake, J. R.

2008-03-01

The EXTRAP T2R is a large aspect ratio Reversed Field Pinch device. The main focus of interest for the experiments is the active feedback control of resistive wall modes [1]. With feedback it has been possible to prolong plasma discharges in T2R from about 20 ms to nearly 100 ms. In a series of experiments in T2R, in H- and D- plasmas with and without feedback, quantitative spectroscopy and passive collector probes have been used to study the flux of metal impurities. Time resolved spectroscopic measurements of Cr and Mo lines showed large metal release towards discharge termination without feedback. Discharge integrated fluxes of Cr, Fe, Ni and Mo were also measured with collector probes at wall position. Reasonable quantitative agreement was found between the spectroscopic and collector probe measurements. The roles of sputtering, thermal evaporation and arcing in impurity production are evaluated based on the composition of the measured impurity flux.

Metal impurity fluxes and plasma-surface interactions in EXTRAP T2R

International Nuclear Information System (INIS)

Bergsaaker, H; Brunsell, P R; Frassinetti, L; Drake, J R; Menmuir, S; Rachlew, E

2008-01-01

The EXTRAP T2R is a large aspect ratio Reversed Field Pinch device. The main focus of interest for the experiments is the active feedback control of resistive wall modes. With feedback it has been possible to prolong plasma discharges in T2R from about 20 ms to nearly 100 ms. In a series of experiments in T2R, in H- and D- plasmas with and without feedback, quantitative spectroscopy and passive collector probes have been used to study the flux of metal impurities. Time resolved spectroscopic measurements of Cr and Mo lines showed large metal release towards discharge termination without feedback. Discharge integrated fluxes of Cr, Fe, Ni and Mo were also measured with collector probes at wall position. Reasonable quantitative agreement was found between the spectroscopic and collector probe measurements. The roles of sputtering, thermal evaporation and arcing in impurity production are evaluated based on the composition of the measured impurity flux

The optimisation of limiter geometry to reduce impurity influx in tokamaks

International Nuclear Information System (INIS)

Matthews, G.F.; McCracken, G.M.; Sewell, P.; Goodall, D.H.J.; Stangeby, P.C.; Pitcher, C.S.

1987-01-01

Conventional limiters are designed to withstand large power loadings and hence are constructed with surfaces at grazing angles to the toroidal magnetic field. As a result any impurities released from the limiter surface are projected towards the centre of the plasma and are poorly screened from it. The impurity control limiter (ICL), an alternative concept which has an inverted geometry is discussed. The ICL shape is designed to direct the impurities towards the wall. Results are presented from a two-dimensional neutral particle code which maps the ionisation of carbon physically sputtered by deuterons from a carbon limiter. This ionisation source is coupled to a one-dimensional impurity transport code which calculates the implied central impurity density. The results demonstrate that the ICL achieves impurity control in two ways. Firstly, many of the sputtered impurities directed towards the wall are not ionised and return to the wall as neutrals. Secondly, much of the ionisation which does occur is located in the scrape-off layer. Here there is a strong ion sink which may also be enhanced by the flow of hydrogenic ions entraining impurity ions created close to the limiter surface. We conclude that a reduction in central impurity density of a factor of 10 is possible in a Tokamak such as DITE provided that the limiter is the main source of impurities. (author)

Anomalous temperature behavior of Sn impurities

International Nuclear Information System (INIS)

Haskel, D.; Shechter, H.; Stern, E.A.; Newville, M.; Yacoby, Y.

1993-01-01

Sn impurities in Pb and Ag hosts have been investigated by Moessbauer effect and in Pb by x-ray-absorption fine-structure (XAFS) studies. The Sn atoms are dissolved up to at least 2 at. % in Pb and up to at least 8 at. % in Ag for the temperature ranges investigated. The concentration limit for Sn-Sn interactions is 1 at. % for Pb and 2 at. % for Ag as determined experimentally by lowering the Sn concentration until no appreciable change occurs in the Moessbauer effect. XAFS measurements verify that the Sn impurities in Pb are dissolved and predominantly at substitutional sites. For both hosts the temperature dependence of the spectral intensities of isolated Sn impurities below a temperature T 0 is as expected for vibrating about a lattice site. Above T 0 the Moessbauer spectral intensity exhibits a greatly increased rate of drop-off with temperature without appreciable broadening. This drop-off is too steep to be explained by ordinary anharmonic effects and can be explained by a liquidlike rapid hopping of the Sn, localized about a lattice site. Higher-entropy-density regions of radii somewhat more than an atomic spacing surround such impurities, and can act as nucleation sites for three-dimensional melting

Interaction of ring dark solitons with ring impurities in Bose-Einstein condensates

International Nuclear Information System (INIS)

Xue Jukui

2005-01-01

The interaction of ring dark solitons/vortexes with the ring-shaped repulsive and attractive impurities in two-dimensional Bose-Einstein condensates is investigated numerically. Very rich interaction phenomena are obtained, i.e., not only the interaction between the ring soliton and the impurity, but also the interaction between vortexes and the impurity. The interaction characters, i.e., snaking of ring soliton, quasitrapping or reflection of ring soliton and vortexes by the impurity, strongly depend on initial ring soliton velocity, impurity strength, initial position of ring soliton and impurity. The numerical results also reveal that ring dark solitons/vortexes can be trapped and dragged by an adiabatically moving attractive ring impurity

Strong quantum scarring by local impurities

Science.gov (United States)

Luukko, Perttu J. J.; Drury, Byron; Klales, Anna; Kaplan, Lev; Heller, Eric J.; Räsänen, Esa

2016-11-01

We discover and characterise strong quantum scars, or quantum eigenstates resembling classical periodic orbits, in two-dimensional quantum wells perturbed by local impurities. These scars are not explained by ordinary scar theory, which would require the existence of short, moderately unstable periodic orbits in the perturbed system. Instead, they are supported by classical resonances in the unperturbed system and the resulting quantum near-degeneracy. Even in the case of a large number of randomly scattered impurities, the scars prefer distinct orientations that extremise the overlap with the impurities. We demonstrate that these preferred orientations can be used for highly efficient transport of quantum wave packets across the perturbed potential landscape. Assisted by the scars, wave-packet recurrences are significantly stronger than in the unperturbed system. Together with the controllability of the preferred orientations, this property may be very useful for quantum transport applications.

Impurities that cause difficulty in stripping actinides from commercial tetraalkylcarbamoylmethylphosphonates

International Nuclear Information System (INIS)

Bahner, C.T.; Shoun, R.R.; McDowell, W.J.

1977-09-01

Dihexyl[(diethylcarbamoyl)methyl]phosphonate (DHDECMP) in diethylbenzene extracts actinides well from 6 M nitric acid solution, but commercially available DHDECMP contains impurities which interfere with stripping the actinides from the organic extract. DHDECMP purified by molecular distillation does not contain these impurities, but the pot residue contains increased concentrations of them. Heating the purified DHDECMP causes the formation of products which interfere with stripping in the same way, suggesting that high temperatures employed in the manufacture of DHDECMP may produce the offending impurities. These impurities can be separated from the heat-decomposed material or the pot residues by dilution with a large volume of hexanes (causing part of the impurities to separate as a second liquid phase) followed by equilibration of the hexane solution with dilute alkali. After the treatment with hexane and dilute alkali, the DHDECMP is readily recovered and functions well in the actinide extraction process. Dibutyl[(dibutylcarbamoyl)methyl]-phosphonate (DBDBCMP) and di(2-ethylhexyl)[(diethylcarbamoyl)-methyl]phosphonate (DEHDECMP) are purified less effectively by these methods. Similar separation methods using diethylbenzene or CCl 4 as solvent do not remove impurities as completely as the hexane process. Impurities can also be removed from a benzene solution of the DHDECMP pot residue by passing it through a column packed with silica gel or diethylaminoethyl cellulose. These impurities have been separated into fractions for analytical examination by use of various solvents and by column chromatography. Hexyl hydrogen [(diethylcarbamoyl)methyl]-phosphonate has been identified tentatively as a principal objectionable impurity. Dihexyl phosphoric acid and possibly dihexylphosphonate have been identified in other fractions

Effects of impurities on radiation damage in InP

International Nuclear Information System (INIS)

Yamaguchi, M.; Ando, K.

1986-01-01

Strong impurity effects upon introduction and annealing behavior of radiation-induced defects in InP irradiated with 1-MeV electrons have been found. The main defect center of 0.37-eV hole trap H4 in p-InP, which must be due to a point defect, is annealed even at room temperature. Its annealing rate is found to be proportional to the 2/3 power of the preirradiation carrier concentration in InP. Moreover, the density of the hole trap H5 (E/sub v/+0.52 eV) in p-InP, which must be due to a point defect--impurity complex, increases with increase in the InP carrier concentration. These results suggest that the radiation-induced defects in InP must recover through long-range diffusion mediated by impurity atoms. A model is proposed in which point defects diffuse to sinks through impurities so as to disappear or bind impurities so as to form point defect--impurity complexes. In addition to the long-range diffusion mechanism, the possibility of charge-state effects responsible for the thermal annealing of radiation-induced defects in InP is also discussed

Association of physical workload and leisure time physical activity with incident mobility limitations

DEFF Research Database (Denmark)

Mänty, M; Møller, A; Nilsson, C

2014-01-01

OBJECTIVES: To examine individual as well as joint associations of physical workload and leisure time physical activity with incident mobility limitations in initially well-functioning middle-aged workers. METHODS: This study is based on 6-year follow-up data of the Danish Longitudinal Study...... on Work, Unemployment and Health. Physical workload was reported at baseline and categorised as light, moderate or heavy. Baseline leisure time physical activity level was categorised as sedentary or active following the current recommendations on physical activity. Incidence of mobility limitations...... with higher workload regardless of level of leisure time physical activity, although the risks tended to be higher among those with sedentary leisure time compared with their active counterparts. All in all, the risk for onset of mobility limitations was highest among those with heavy workload combined...

Use of a Mobile Device Simulation as a Preclass Active Learning Exercise.

Science.gov (United States)

Keegan, Robert D; Oliver, M Cecile; Stanfill, Teresa J; Stevens, Kevin V; Brown, Gary R; Ebinger, Michael; Gay, John M

2016-01-01

Research shows that preclass activities introducing new material can increase student performance. In an effort to engage students in an active learning, preclass activity, the authors developed a mobile application. Eighty-four nursing students were assigned a preclass reading exercise, whereas 32 students completed the preclass simulation scenario on their mobile device. All students completed the same electronic fetal monitoring (EFM) quiz 1 week following the lecture. The effects of reading or simulation on student quiz performance was evaluated with a student's paired t test, using an alpha of .05. Students completing the preclass simulation scored higher on the EFM quiz, compared with students assigned the preclass reading (85% versus 70% correct answers, p = .01). Student survey data indicated that the mobile device simulation was perceived as an engaging and desirable instructional tool. Nursing students completing the mobile device EFM preclass simulation outperformed the students who were given the traditional reading assignment. Copyright 2016, SLACK Incorporated.

Synthesis, Isolation and Characterization of Process-Related Impurities in Oseltamivir Phosphate

Directory of Open Access Journals (Sweden)

Yogesh Kumar Sharma

2012-01-01

Full Text Available Three known impurities in oseltamivir phosphate bulk drug at level 0.1% (ranging from 0.05-0.1% were detected by gradient reverse phase high performance liquid chromatography. These impurities were preliminarily identified by the mass number of the impurities. Different experiments were conducted and finally the known impurities were synthesized and characterized.

Chromatographic resolution of closely related species in pharmaceutical chemistry: dehalogenation impurities and mixtures of halogen isomers.

Science.gov (United States)

Regalado, Erik L; Zhuang, Ping; Chen, Yadan; Makarov, Alexey A; Schafer, Wes A; McGachy, Neil; Welch, Christopher J

2014-01-07

In recent years, the use of halogen-containing molecules has proliferated in the pharmaceutical industry, where the incorporation of halogens, especially fluorine, has become vitally important for blocking metabolism and enhancing the biological activity of pharmaceuticals. The chromatographic separation of halogen-containing pharmaceuticals from associated isomers or dehalogenation impurities can sometimes be quite difficult. In an attempt to identify the best current tools available for addressing this important problem, a survey of the suitability of four chromatographic method development platforms (ultra high-performance liquid chromatography (UHPLC), core shell HPLC, achiral supercritical fluid chromatography (SFC) and chiral SFC) for separating closely related mixtures of halogen-containing pharmaceuticals and their dehalogenated isosteres is described. Of the 132 column and mobile phase combinations examined for each mixture, a small subset of conditions were found to afford the best overall performance, with a single UHPLC method (2.1 × 50 mm, 1.9 μm Hypersil Gold PFP, acetonitrile/methanol based aqueous eluents containing either phosphoric or perchloric acid with 150 mM sodium perchlorate) affording excellent separation for all samples. Similarly, a survey of several families of closely related halogen-containing small molecules representing the diversity of impurities that can sometimes be found in purchased starting materials for synthesis revealed chiral SFC (Chiralcel OJ-3 and Chiralpak IB, isopropanol or ethanol with 25 mM isobutylamine/carbon dioxide) as well as the UHPLC (2.1 × 50 mm, 1.8 μm ZORBAX RRHD Eclipse Plus C18 and the Gold PFP, acetonitrile/methanol based aqueous eluents containing phosphoric acid) as preferred methods.

Activity-Based Support for Mobility and Collaboration in Ubiquitous Computing

DEFF Research Database (Denmark)

Bardram, Jacob Eyvind

2004-01-01

is to: (1) support human activity by managing its collection of work tasks on a computer, (2) support mobility by distributing activities across heterogeneous computing environments, (3) support asynchronous collaboration by allowing several people to participate in an activity, and (4) support...

Defining a Roadmap Towards Comparative Research in Online Activity Recognition on Mobile Phones

NARCIS (Netherlands)

Shoaib, M.; Bosch, S.; Durmaz, O.; Scholten, Johan; Havinga, Paul J.M.

2015-01-01

Many context-aware applications based on activity recognition are currently using mobile phones. Most of this work is done in an offline way. However, there is a shift towards an online approach in recent studies, where activity recognition systems are implemented on mobile phones. Unfortunately,

Spectroscopic studies of carbon impurities in PISCES-A

International Nuclear Information System (INIS)

Ra, Y.; Hirooka, Y.; Leung, W.K.; Conn, R.W.; Pospieszczyk, A.

1989-08-01

The graphite used for the limiter of the tokamak reactor produces carbon-containing molecular impurities as a result of the interactions with the edge plasma. The behavior of these molecular impurities has been studied using emission spectroscopy. The present study includes: finding molecular bands and atomic lines in the visible spectral range which can be used for the study of the molecular impurities, studying the breakup processes of the molecular impurities on their way from the source into the plasma, developing a spectroscopic diagnostic method for the absolute measurement of the molecular impurity flux resulting from graphite erosion. For these studies, carbon-containing molecules such as CH 4 , C 2 H 2 , C 2 H 4 , and CO 2 were injected into the tokamak-boundary,like plasma generated by PISCES-A. The spectrograms of these gases were taken. Many useful bands and lines were determined from the spectrograms. The breakup processes of these gases were studied by observing the spatial profiles of the emission of the molecules and their radicals for different plasma conditions. For the absolute measurement of the eroded molecular impurity flux, the photon efficiency of the lines and bands were found by measuring the absolute number of the emitted photons and injected gas molecules. The chemical sputtering yield of graphite by hydrogen plasma was spectroscopically measured using the previously obtained photon efficiencies. It showed good agreement with results obtained by weight loss measurements. 16 refs., 7 figs., 1 tab

The role of demographic and motivational factors on mobile commerce usage activities in South Africa

Directory of Open Access Journals (Sweden)

Malcolm Cullen

2018-03-01

Full Text Available Background: Many studies have examined the mobile commerce phenomenon and most of these have focused on understanding the organisational and environmental factors that affect its adoption. Few have examined how an individual’s characteristics and their perceived motivational appetite affect their mobile commerce usage and specifically the activities they engage in.   Objectives: This study examines the role of demographics (individuals’ characteristics and motivational factors on mobile commerce usage activities from the South African perspective.   Method: An objective approach and a positivistic stance were followed. The research model and instrument from earlier studies by Chong (2013a were contextualised to suit this study. Data collection was done through an online questionnaire, 88 responses were received and 81 used for data analysis.   Results: The findings show that age is significantly related to mobile commerce transactions, and one’s education status influences the following mobile commerce usage activities: transactions and location-based services. One’s gender influences how one uses mobile commerce. A significant relationship between all three motivational variables and mobile commerce usage activities is evident.   Conclusion: The findings provide the financial services industry and providers of mobile commerce offerings with a better understanding of the relationships between customer demographics and the mobile commerce activities they engage in. An additional variable of customer income has been identified for future studies to better understand the relationship.

A validated stability-indicating LC method for the separation of enantiomer and potential impurities of Linezolid using polar organic mode

Directory of Open Access Journals (Sweden)

T. Satyanarayana Raju

2012-08-01

Full Text Available Although a number of methods are available for evaluating Linezolid and its possible impurities, a common method for separation if its potential impurities, degradants and enantiomer in a single method with good efficiency remain unavailable. With the objective of developing an advanced method with shorter runtimes, a simple, precise, accurate stability-indicating LC method was developed for the determination of purity of Linezolid drug substance and drug products in bulk samples and pharmaceutical dosage forms in the presence of its impurities and degradation products. This method is capable of separating all the related substances of Linezolid along with the chiral impurity. This method can also be used for the estimation of assay of Linezolid in drug substance as well as in drug product. The method was developed using Chiralpak IA (250 mm×4.6 mm, 5 μm column. A mixture of acetonitrile, ethanol, n-butyl amine and trifluoro acetic acid in 96:4:0.10:0.16 (v/v/v/v ratio was used as a mobile phase. The eluted compounds were monitored at 254 nm. Linezolid was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal and photolytic degradation. The degradation products were well resolved from main peak and its impurities, proving the stability-indicating power of the method. The developed method was validated as per International Conference on Harmonization (ICH guidelines with respect to specificity, limit of detection, limit of quantification, precision, linearity, accuracy, robustness and system suitability. Keywords: HPLC, Linezolid, Validation, Polar organic mode, Stability-indicating

Oscillations of quantum transport through double-AB rings with magnetic impurity

International Nuclear Information System (INIS)

Gao Yingfang; Liang, J-Q

2006-01-01

We have studied the effect of impurity scattering on the quantum transport through double AB rings in the presence of spin-flipper in the middle lead in terms of one-dimensional quantum waveguide theory. The electron interacts with the impurity through the exchange interaction leading to spin-flip scattering. Transmissions in the spin-flipped and non-spin-flipped channels are calculated explicitly. It is found that the overall transmission and the conductance are distorted due to the impurity scattering. The extent of distortion not only depends on the strength of the impurity potential but also on the impurity position. Moreover, the transmission probability and the conductance are modulated by the magnetic flux, the size of the ring and the impurity potential strength as well

Investigation of impurity defects in α-iron by molecular dynamics method

International Nuclear Information System (INIS)

Kevorkyan, Yu.R.

1986-01-01

Investigation of the configuration of impurity defects in α-iron by the molecular dynamics method is presented. The Jhonson model potential has been used to calculate the interaction of matrix atoms. The impurity-matrix atom interaction is described by the same form of the potential shifted along the axis of interatomic distances for a definite value. The correspondence between the shift value and change in the radius of the impurity defect is established on the basis of calculation of the relaxation volume. Possible configurations of the impurity - interstitial matrix atom complexes are obtained for the given model of the impurity defect, dimensional boundaries of possible transitions between different configurations are determined. Formation and bound energies, relaxation volumes of impurity defects are calculated

Anomalous diffusion, clustering, and pinch of impurities in plasma edge turbulence

DEFF Research Database (Denmark)

Priego, M.; Garcia, O.E.; Naulin, V.

2005-01-01

The turbulent transport of impurity particles in plasma edge turbulence is investigated. The impurities are modeled as a passive fluid advected by the electric and polarization drifts, while the ambient plasma turbulence is modeled using the two-dimensional Hasegawa-Wakatani paradigm for resistive...... drift-wave turbulence. The features of the turbulent transport of impurities are investigated by numerical simulations using a novel code that applies semi-Lagrangian pseudospectral schemes. The diffusive character of the turbulent transport of ideal impurities is demonstrated by relative...... orientation determined by the charge of the impurity particles. Second, a radial pinch scaling linearly with the mass-charge ratio of the impurities is discovered. Theoretical explanation for these observations is obtained by analysis of the model equations. (C) 2005 American Institute of Physics....

Depolarization of diffusing spins by paramagnetic impurities

International Nuclear Information System (INIS)

Schillaci, M.E.; Hutson, R.L.; Heffner, R.H.; Leon, M.; Dodds, S.A.; Estle, T.L.

1981-01-01

We study the depolarization of diffusing spins (muons) interacting with dilute paramagnetic impurities in a solid using a simple computational model which properly treats the muon motion and preserves correct muon-impurity distances. Long-range (dipolar) and nearest-neighbor (contact) interactions are treated together. Diffusion parameters are deduced and model comparisons made for AuGd (300 ppm). (orig.)

Innovative sludge pretreatment technology for impurity separation using micromesh.

Science.gov (United States)

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.

Carbon impurity transport around limiters in the DITE tokamak

International Nuclear Information System (INIS)

Pitcher, C.S.; Stangeby, P.C.; Goodall, D.H.J.; Matthews, G.F.; McCracken, G.M.

1989-01-01

The transport of impurity ions originating at the limiter in a tokamak is critically dependent on the location of the ion in the boundary plasma. In the confined plasma, just inboard of the limiter, impurity ions will disperse freely into the discharge whilst in the scrape-off layer the pre-sheath plasma flow and the associated ambipolar electric field may tend to sweep impurities back to the limiter surface. In this paper we have studied, both by experiment and by theory, the transport of carbon impurity ions in the vicinity of the limiter. By comparing experimental measurements of the spatial distributions of impurities around the limiter with that predicted from a Monte Carlo computer code it appears that the parallel dispersal on closed field lines in the confined plasma is consistent with classical transport processes and that in the scrape-off layer the dispersal is indeed impeded by the pre-sheath plasma flow. (orig.)

Interactions of Ultracold Impurity Particles with Bose-Einstein Condensates

Science.gov (United States)

2015-06-23

AFRL-OSR-VA-TR-2015-0141 INTERACTIONS OF ULTRACOLD IMPURITY PARTICLES WITH BOSE- EINSTEIN CONDENSATES Georg Raithel UNIVERSITY OF MICHIGAN Final...SUBTITLE Interactions of ultracold impurity particles with Bose- Einstein Condensates 5a. CONTRACT NUMBER FA9550-10-1-0453 5b. GRANT NUMBER 5c...Interactions of ultracold impurity particles with Bose- Einstein Condensates Contract/Grant #: FA9550-10-1-0453 Reporting Period: 8/15/2010 to 2/14

Impurity production and acceleration in CTIX

Energy Technology Data Exchange (ETDEWEB)

Buchenauer, D. [Sandia National Laboratories, MS-9161, P.O. Box 969, Livermore, CA 94550 (United States)], E-mail: dabuche@sandia.gov; Clift, W.M. [Sandia National Laboratories, MS-9161, P.O. Box 969, Livermore, CA 94550 (United States); Klauser, R.; Horton, R.D. [CTIX Group, University of California at Davis, Davis, CA 95616 (United States); Howard, S.J. [General Fusion Inc., Burnaby, BC V5A 3H4 (Canada); Brockington, S.J. [HyperV Technologies Corp., Chantilly, VA 20151 (United States); Evans, R.W.; Hwang, D.Q. [CTIX Group, University of California at Davis, Davis, CA 95616 (United States)

2009-06-15

The Compact Toroid Injection Experiment (CTIX) produces a high density, high velocity hydrogen plasma that maintains its configuration in free space on a MHD resistive time scale. In order to study the production and acceleration of impurities in the injector, several sets of silicon collector probes were exposed to spheromak-like CT's exiting the accelerator. Elemental analysis by Auger Electron Spectroscopy indicated the presence of O, Al, Fe, and Cu in films up to 200 A thickness (1000 CT interactions). Using a smaller number of CT interactions (10-20), implantation of Fe and Cu was measured by Auger depth profiling. The amount of impurities was found to increase with accelerating voltage and number of CT interactions while use of a solenoidal field reduced the amount. Comparison of the implanted Fe and Cu with TRIM simulations indicated that the impurities were traveling more slowly than the hydrogen CT.

Transport properties of field-effect transistor with Langmuir-Blodgett films of C60 dendrimer and estimation of impurity levels

Science.gov (United States)

Kawasaki, Naoko; Nagano, Takayuki; Kubozono, Yoshihiro; Sako, Yuuki; Morimoto, Yu; Takaguchi, Yutaka; Fujiwara, Akihiko; Chu, Chih-Chien; Imae, Toyoko

2007-12-01

Field-effect transistor (FET) device has been fabricated with Langmuir-Blodgett films of C60 dendrimer. The device showed n-channel normally off characteristics with the field-effect mobility of 2.7×10-3cm2V-1s-1 at 300K, whose value is twice as high as that (1.4×10-3cm2V-1s-1) for the FET with spin-coated films of C60 dendrimer. This originates from the formation of ordered π-conduction network of C60 moieties. From the temperature dependence of field-effect mobility, a structural phase transition has been observed at around 300K. Furthermore, the density of states for impurity levels was estimated in the Langmuir-Blodgett films.

Modeling of the Microchemistry for Diffusion of Selected Impurities in Uranium

International Nuclear Information System (INIS)

Kirkpatrick, J. R.; Bullock, J.S. IV

2001-01-01

Unalloyed metallic uranium used in some work done at Y-12 contains small quantities of impurities, the three most significant of which are carbon, iron, and silicon. During metallurgical processing, as the metal cools from a molten condition towards room temperature, the metallic matrix solution becomes supersaturated in each of the impurities whose concentration exceeds the solubility limit. Many impurity atoms form compounds with uranium that precipitate out of the solution, thus creating and growing inclusions. The objective of the present work is to study the distribution of impurity atoms about some of the inclusions, with a view toward examining the effect of the interaction between inclusions on the impurity atom distribution. The method used is time-dependent mass diffusion from the supersaturated solution to the surfaces of the inclusions. Micrographs of metal samples suggest that the inclusions form in successive stages. After each inclusion forms, it begins to draw impurity atoms from its immediate vicinity, thus altering the amounts and distributions of impurity atoms available for formation and growth of later inclusions. In the present work, a one-dimensional spherical approximation was used to simulate inclusions and their regions of influence. A first set of calculations was run to simulate the distribution of impurity atoms about the largest inclusions. Then, a second set of calculations was run to see how the loss of impurity atoms to the largest inclusions might affect the distribution of impurity atoms around the next stage of inclusions. Plots are shown for the estimated distributions of impurity atoms in the region of influence about the inclusions for the three impurities studied. The authors believe that these distributions are qualitatively correct. However, there is enough uncertainty about precisely when inclusions nucleate and begin to grow that one should not put too much reliance on the quantitative results. This work does provide a

Impurity-induced tuning of quantum-well States in spin-dependent resonant tunneling.

Science.gov (United States)

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

Continuous-time quantum Monte Carlo impurity solvers

Science.gov (United States)

Gull, Emanuel; Werner, Philipp; Fuchs, Sebastian; Surer, Brigitte; Pruschke, Thomas; Troyer, Matthias

2011-04-01

Continuous-time quantum Monte Carlo impurity solvers are algorithms that sample the partition function of an impurity model using diagrammatic Monte Carlo techniques. The present paper describes codes that implement the interaction expansion algorithm originally developed by Rubtsov, Savkin, and Lichtenstein, as well as the hybridization expansion method developed by Werner, Millis, Troyer, et al. These impurity solvers are part of the ALPS-DMFT application package and are accompanied by an implementation of dynamical mean-field self-consistency equations for (single orbital single site) dynamical mean-field problems with arbitrary densities of states. Program summaryProgram title: dmft Catalogue identifier: AEIL_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEIL_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: ALPS LIBRARY LICENSE version 1.1 No. of lines in distributed program, including test data, etc.: 899 806 No. of bytes in distributed program, including test data, etc.: 32 153 916 Distribution format: tar.gz Programming language: C++ Operating system: The ALPS libraries have been tested on the following platforms and compilers: Linux with GNU Compiler Collection (g++ version 3.1 and higher), and Intel C++ Compiler (icc version 7.0 and higher) MacOS X with GNU Compiler (g++ Apple-version 3.1, 3.3 and 4.0) IBM AIX with Visual Age C++ (xlC version 6.0) and GNU (g++ version 3.1 and higher) compilers Compaq Tru64 UNIX with Compq C++ Compiler (cxx) SGI IRIX with MIPSpro C++ Compiler (CC) HP-UX with HP C++ Compiler (aCC) Windows with Cygwin or coLinux platforms and GNU Compiler Collection (g++ version 3.1 and higher) RAM: 10 MB-1 GB Classification: 7.3 External routines: ALPS [1], BLAS/LAPACK, HDF5 Nature of problem: (See [2].) Quantum impurity models describe an atom or molecule embedded in a host material with which it can exchange electrons. They are basic to nanoscience as

Impurity adsorption mechanism of borax for a suspension growth condition: A comparison of models and experimental data

International Nuclear Information System (INIS)

Al-Jibbouri, Sattar; Ulrich, Joachim

2004-01-01

A fluidized bed crystallizer is employed to investigate the growth and dissolution rates of MgSO 4 .7H 2 O from aqueous solutions in the presence of borax as impurity at 25 C. By adding 0.5, 1, 2 and 5 wt % of impurity the pH value changes from 6.7 to 7.11, while the saturation temperature shifts to 24.8, 24.4, 24 and 23.1 C, respectively. The data on crystal growth rates from aqueous solutions as a function of impurity concentration are discussed from the standpoint of Cabrera and Vermileya, and Kubota and Mullin. The value of the impurity effect, αθ eq , determined from analysis of the data on growth kinetics was found to be in good agreement with the value obtained from direct adsorption experiments. The estimated value of the average spacing between the adjacent adsorption active sites and the average distance between the neighbouring impurity-adsorbed sites are also reported. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Impurity transport calculations for the limiter shadow region of a tokamak

International Nuclear Information System (INIS)

Claassen, H.A.; Repp, H.

1981-01-01

Impurity transport calculations are presented for the scrape-off layer of a tokamak with a poloidal ring limiter. The theory is based on the drift-kinetic equations for the impurity ions in their different ionization states. It is developed in the limit of low impurity concentrations under due consideration of electron impact ionization, Coulomb collisions with hydrogen ions streaming onto a neutralizing surface, a convection along the magnetic field, and a radial drift. The background plasma and the impurity sources at the walls enter the theory as input parameters. Numerical results are given for the radial profiles of density, temperature, particle flux, and energy flux of wall-released impurity ions as well as for the screening efficiency of the scrape-off layer neglecting impurity re-emission from the limiter. (author)

Radiation-chemical disinfection of dissolved impurities and environmental protection

International Nuclear Information System (INIS)

Petrukhin, N.V.; Putilov, A.V.

1986-01-01

Radiation-chemical neutralization of dissolved toxic impurities formed in the production processes of different materials, while modern plants being in use, is considered. For the first time the processes of deep industrial waste detoxication and due to this peculiarities of practically thorough neutralization of dissolved toxic impurities are considered. Attention is paid to devices and economic factors of neutralization of dissolved toxic impurities. The role of radiation-chemical detoxication for environment protection is considered

Mobility management in mobile IP

Science.gov (United States)

Medidi, Sirisha; Golshani, Forouzan

2002-07-01

There is an emerging interest in integrating mobile wireless communication with the Internet based on the Ipv6 technology. Many issues introduced by the mobility of users arise when such an integration is attempted. This paper addresses the problem of mobility management, i.e., that of tracking the current IP addresses of mobile terminals and sustaining active IP connections as mobiles move. The paper presents some architectural and mobility management options for integrating wireless access to the Internet. We then present performance results for Mobile IPv4, route optimization and Mobile IPv6.

Effects of magnetic impurity scattering on superfluid 3He in aerogel

Science.gov (United States)

Aoyama, Kazushi; Ikeda, Ryusuke

2009-02-01

We investigate impurity effects on superfluid 3He in aerogel whose surface is not coated with 4He, different from most experimental situations. In systems with no 4He coating, spins of solid 3He absorbed on the aerogel surface are active and interact with spins of quasiparticles relevant to superfluidity and, for this reason, such an aerogel is treated as magnetic scatterers. It is found that, in the ABM pairing state affected by magnetic scatterings, not only the l-vector but also the d-vector has no long-ranged orientational order, and that the strong-coupling correction due to impurity scatterings is less suppressed than that in the nonmagnetic case, implying an expansion of the A-like phase region.

Effect of impurity radiation on tokamak equilibrium

International Nuclear Information System (INIS)

Rebut, P.H.; Green, B.J.

1977-01-01

The energy loss from a tokamak plasma due to the radiation from impurities is of great importance in the overall energy balance. Taking the temperature dependence of this loss for two impurities characteristic of those present in existing tokamak plasmas, the condition for radial power balance is derived. For the impurities considered (oxygen and iron) it is found that the radiation losses are concentrated in a thin outer layer of the plasma and the equilibrium condition places an upper limit on the plasma paraticle number density in this region. This limiting density scales with mean current density in the same manner as is experimentally observed for the peak number density of tokamak plasmas. The stability of such equilibria is also discussed. (author)

High-performance liquid chromatographic determination of pantoprazole and its main impurities in pharmaceuticals.

Science.gov (United States)

Letica, Jelena; Marković, Slavko; Zirojević, Jelena; Nikolić, Katarina; Agbaba, Danica

2010-01-01

An RP-HPLC method for simultaneous separation and quantification of pantoprazole and its five main impurities in pharmaceutical formulations was developed and validated. The separation was accomplished on a Zorbax Eclipse XDB C18 column (5 microm particle size, 150 x 4.6 mm id) using a gradient with mobile phase A [buffer-acetonitrile (70 + 30, v/v)], and mobile phase B [buffer-acetonitrile (30 + 70, v/v)]. The buffer was 0.01 M ammonium acetate solution with addition of 1 mL triethylamine/L of the solution, adjusted to pH 4.5 with orthophosphoric acid. The eluent flow rate was 1 mL/min, the temperature of the column was 30 degrees C, and the eluate was monitored at 290 nm. Linearity (r = 0.999), recovery (97.6-105.8%), RSD (0.55-1.90%), and LOQ (0.099-1.48 microg/mL) were evaluated and found to be satisfactory. The proposed method can be used for simultaneous identification and quantification of the analyzed compounds in pharmaceutical formulations.

Effects of helium impurities on superalloys

International Nuclear Information System (INIS)

Selle, J.E.

1977-07-01

A review of the literature on the effects of helium impurities on superalloys at elevated temperatures was undertaken. The actual effects of these impurities vary depending on the alloy, composition of the gas atmosphere, and temperature. In general, exposure in helium produces significant but not catastrophic changes in the structure and properties of the alloys. The effects of these treatments on the structure, creep, fatigue, and mechanical properties of the various alloys are reviewed and discussed. Suggestions for future work are presented

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

Science.gov (United States)

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.

Identification and control of unspecified impurity in trimetazidine dihydrochloride tablet formulation

Science.gov (United States)

Jefri; Puspitasari, A. D.; Talpaneni, J. S. R.; Tjandrawinata, R. R.

2018-04-01

Trimetazidine dihydrochloride is an anti-ischemic metabolic agent which is used as drug for angina pectoris treatment. The drug substance monograph is available in European Pharmacopoeia and British Pharmacopoeia, while the drug product monograph is not available in any of the pharmacopoeias. During development of trimetazidine dihydrochloride tablet formulation, we found increase of an unspecified impurity during preliminary stability study. The unspecified impurity was identified by high performance liquid chromatography coupled with mass spectrometry (LC-MS) and the molecular weight obtained was matching with the molecular weight of N-formyl trimetazidine (m/z 295). Further experiments were performed to confirm the suspected result by injecting the impurity standard and spiking formic acid into the drug substance. The retention time of N-formyl trimetazidine was similar to the unspecified impurity in drug product. Even spiking of formic acid into drug substance showed that the suspected impurity increased with increasing concentration of formic acid. The proposed mechanism of impurity formation is via amidation of piperazine moiety of trimetazidine by formic acid which present as residual solvent in tablet binder used in the formulation. Subsequently, the impurity in our product was controlled by choosing the primary packaging which could minimize the formation of impurity.

Investigation of the impurity transport in the ASDEX tokamak by spectroscopical methods

International Nuclear Information System (INIS)

Krieger, K.W.

1990-12-01

Plasma impurities: a central problem of controlled thermonuclear fusion; magnetic plasma confinement in a Tokamak; methods to the determination of plasma impurity transport coefficients - by temporally modulated gas admission; the transport equation for impurities; neoclassical and anomalous transport; harmonic analysis of time-dependent signals; solutions of the transport equation; experimental equipment and measurements; measuring results - consistency of simple transport models with radial phase measurements; linearity of the transport processes; plasma disturbance by impurity injection; determination of the diffusion coefficient by simplified transport models; comparison of transport models for impurities and background plasma; measurements of the impurity transport at the plasma edge by high modulation frequencies. (AH)

Impurity effects of hydrogen isotope retention on boronized wall in LHD

International Nuclear Information System (INIS)

Oya, Yasuhisa; Okuno, Kenji; Ashikawa, Naoko; Nishimura, Kiyohiko; Sagara, Akio

2010-11-01

The impurity effect on hydrogen isotopes retention in the boron film deposited in LHD was evaluated by means of XPS and TDS. It was found that the impurity concentrations in boron film were increased after H-H main plasma exposure in LHD. The ratio of hydrogen retention trapped by impurity to total hydrogen retention during H-H main plasma exposure was reached to 70%, although that of deuterium retention by impurity in D 2 + implanted LHD-boron film was about 35%. In addition, the dynamic chemical sputtering of hydrogen isotopes with impurity as the form of water and / or hydrocarbons was occurred by energetic hydrogen isotopes irradiation. It was expected that the enhancement of impurity concentration during plasma exposure in LHD would induce the dynamic formation of volatile molecules and their re-emission to plasma. These facts would prevent stable plasma operation in LHD, concluding that the dynamic impurity behavior in boron film during plasma exposure is one of key issues for the steady-state plasma operation in LHD. (author)

Electronic transport properties of Ti-impurity band in Si

Energy Technology Data Exchange (ETDEWEB)

Olea, J; Gonzalez-Diaz, G; Pastor, D; Martil, I [Departamento de Fisica Aplicada III (Electricidad y Electronica), Facultad de Ciencias, Fisicas, Universidad Complutense, E-28040 Madrid (Spain)

2009-04-21

In this paper we show that pulsed laser melted high dose implantation of Ti in Si, above the Mott transition, produces an impurity band (IB) in this semiconductor. Using the van der Pauw method and Hall effect measurements we find strong laminated conductivity at the implanted layer and a temperature dependent decoupling between the Ti implanted layer (TIL) and the substrate. The conduction mechanism from the TIL to the substrate shows blocking characteristics that could be well explained through IB theory. Using the ATLAS code we can estimate the energetic position of the IB at 0.36 eV from the conduction band, the density of holes in this band which is closely related to the Ti atomic density and the hole mobility in this band. Band diagrams of the structure at low and high temperatures are also simulated in the ATLAS framework. The simulation obtained is fully coherent with experimental results.

Electronic transport properties of Ti-impurity band in Si

International Nuclear Information System (INIS)

Olea, J; Gonzalez-Diaz, G; Pastor, D; Martil, I

2009-01-01

In this paper we show that pulsed laser melted high dose implantation of Ti in Si, above the Mott transition, produces an impurity band (IB) in this semiconductor. Using the van der Pauw method and Hall effect measurements we find strong laminated conductivity at the implanted layer and a temperature dependent decoupling between the Ti implanted layer (TIL) and the substrate. The conduction mechanism from the TIL to the substrate shows blocking characteristics that could be well explained through IB theory. Using the ATLAS code we can estimate the energetic position of the IB at 0.36 eV from the conduction band, the density of holes in this band which is closely related to the Ti atomic density and the hole mobility in this band. Band diagrams of the structure at low and high temperatures are also simulated in the ATLAS framework. The simulation obtained is fully coherent with experimental results.

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

Energy Technology Data Exchange (ETDEWEB)

Valerio, Luis G., E-mail: luis.valerio@fda.hhs.gov [Science and Research Staff, Office of Pharmaceutical Science, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, MD 20993–0002 (United States); Cross, Kevin P. [Leadscope, Inc., 1393 Dublin Road, Columbus, OH, 43215–1084 (United States)

2012-05-01

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 describe 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

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

International Nuclear Information System (INIS)

Valerio, Luis G.; Cross, Kevin P.

2012-01-01

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 describe 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.

Effect of suprathermal electrons on the impurity ionization state

International Nuclear Information System (INIS)

Ochando, M A; Medina, F; Zurro, B; McCarthy, K J; Pedrosa, M A; Baciero, A; Rapisarda, D; Carmona, J M; Jimenez, D

2006-01-01

The effect of electron cyclotron resonance heating induced suprathermal electron tails on the ionization of iron impurities in magnetically confined plasmas is investigated. The behaviour of plasma emissivity immediately after injection provides evidence of a spatially localized 'shift' towards higher charge states of the impurity. Bearing in mind that the non-inductive plasma heating methods generate long lasting non-Maxwellian distribution functions, possible implications on the deduced impurity transport coefficients, when fast electrons are present, are discussed

Impurity levels: corrections to the effective mass approximation

International Nuclear Information System (INIS)

Bentosela, F.

1977-07-01

Some rigorous results concerning the effective mass approximation used for the calculation of the impurity levels in semiconductors are presented. Each energy level is expressed as an asymptotic series in the inverse of the dielectric constant K, in the case where the impurity potential is 1/μ

Damping of elastic waves in crystals with impurities

International Nuclear Information System (INIS)

Lemanov, V.V.; Petrov, A.V.; Akhmedzhanov, F.R.; Nasyrov, A.N.

1979-01-01

Elastic wave damping and thermal conductivity of NaCl-NaBr and Y 3 AL 5 O 12 crystals with Er impurity has been examined. The experimental results on a decrease in elastic wave damping in such crystals are analyzed in the framework of the Ahiezer damping theory. The measurements were made in the frequency range of 300-1500 MHz in propagation of longitudinal and transverse elastic waves along the [100] and [110] directions. At 10 % concentration of erbium impurity the transverse wave damping decreases by a factor of three, and for longitudinal waves by a factor of two in NaBr:Cl crystals, and by approximately 10 and 30 % for NaBr:Cl and Y 3 Al 5 O 12 :Er crystals, respectively. In Y 3 Al 5 O 12 crystals, unlike NaCl-NaBr crystals, no noticeable anisotropy of damping is observed. The transVerse wave damping in impurity crystals has been shown to increase significantly with decreasing temperature and increasing the impurity concentration

Impurity investigations in the boundary layer of the DITE tokamak

International Nuclear Information System (INIS)

McCracken, G.M.; Partridge, J.W.; Erents, S.K.; Sofield, C.J.; Ferguson, S.M.

1982-01-01

The results obtained in the present investigation show large fluctuations both during discharges and from one discharge to the next. The radial density gradient of impurities in the boundary is not large. It is clear that the density and in particular dn/dt can have a strong effect on the impurity level. However there are apparently a number of other factors causing changes in impurity level which have not been well controlled in the present experiments. Possibilities include flaking from the walls, and changes in the level of the light impurities, oxygen and carbon, in the discharges. (orig./RW)

Investigation of impurity-helium solid phase decomposition

International Nuclear Information System (INIS)

Boltnev, R.E.; Gordon, E.B.; Krushinskaya, I.N.; Martynenko, M.V.; Pel'menev, A.A.; Popov, E.A.; Khmelenko, V.V.; Shestakov, A.F.

1997-01-01

The element composition of the impurity-helium solid phase (IHSP), grown by injecting helium gas jet, involving Ne, Ar, Kr, and Xe atoms and N 2 molecules, into superfluid helium, has been studied. The measured stoichiometric ratios, S = N H e / N I m, are well over the values expected from the model of frozen together monolayer helium clusters. The theoretical possibility for the freezing of two layers helium clusters is justified in the context of the model of IHSP helium subsystem, filled the space between rigid impurity centers. The process of decomposition of impurity-helium (IH)-samples taken out of liquid helium in the temperature range 1,5 - 12 K and the pressure range 10-500 Torr has been studied. It is found that there are two stages of samples decomposition: a slow stage characterized by sample self cooling and a fast one accompanied by heat release. These results suggest, that the IHSP consists of two types of helium - weakly bound and strongly bound helium - that can be assigned to the second and the first coordination helium spheres, respectively, formed around heavy impurity particles. A tendency for enhancement of IHSP thermo stability with increasing the impurity mass is observed. Increase of helium vapor pressure above the sample causes the improvement of IH sample stability. Upon destruction of IH samples, containing nitrogen atoms, a thermoluminescence induced by atom recombination has been detected in the temperature region 3-4,5 K. This suggests that numerous chemical reactions may be realized in solidified helium

Impurity studies in fusion devices using laser-fluorescence-spectroscopy

International Nuclear Information System (INIS)

Husinsky, W.R.

1980-08-01

Resonance fluorescence excitation of neutral atoms using tunable radiation from dye lasers offers a number of unique advantages for impurity studies in fusion devices. Using this technique, it is possible to perform local, time-resolved measurements of the densities and velocity distributions of metallic impurities in fusion devices without disturbing the plasma. Velocities are measured by monitoring the fluorescence intensity while tuning narrow bandwidth laser radiation through the Doppler - broadened absorbtion spectrum of the transition. The knowledge of the velocity distribution of neutral impurities is particularly useful for the determination of impurity introduction mechanisms. The laser fluorescence technique will be described in terms of its application to metallic impurities in fusion devices and related laboratory experiments. Particular attention will be given to recent results from the ISX-B tokamak using pulsed dye lasers where detection sensitivities for neutral Fe of 10 6 atoms/cm 3 with a velocity resolution of 600 m/sec (0.1 eV) have been achieved. Techniques for exciting plasma particles (H,D) will also be discussed

Orbit effects on impurity transport in a rotating plasma

International Nuclear Information System (INIS)

Wong, K.L.; Cheng, C.Z.

1988-01-01

In 1985, very high ion temperature plasmas were first produced in TFTR with co-injecting neutral beams in low current, low density plasmas. This mode of operation is called the energetic ion mode in which the plasma rotates at very high speed. It was found that heavy impurities injected into these plasmas diffused out very quickly. In this paper, the authors calculate the impurity ion orbits in a rotating tokamak plasma based on the equation of motion in the frame that rotates with the plasma. It is shown that heavy particles in a rotating plasma can drift away from magnetic surfaces significantly faster. Particle orbits near the surface of a rotating tokamak are also analyzed. During impurity injection experiments, freshly ionized impurities near the plasma surface are essentially stationary in the laboratory frame and they are counter-rotating in the plasma frame with co-beam injection. The results are substantiated by numeral particle simulation. The computer code follows the impurity guiding center positions by integrating the equation of motion with the second order predictor-corrector method

Resonant scattering on impurities in the quantum Hall effect

International Nuclear Information System (INIS)

Gurvitz, A.

1994-06-01

We developed a new approach to carrier transport between the edge states via resonant scattering on impurities, which is applicable both for short and long range impurities. A detailed analysis of resonant scattering on a single impurity is performed. The results used for study of the inter-edge transport by multiple resonant hopping via different impurities' site. We found the total conductance can be obtained from an effective Schroedinger equation with constant diagonal matrix elements in the Hamiltonian, where the complex non-diagonal matrix elements are the amplitudes of a carrier hopping between different impurities. It is explicitly shown how the complex phase leads to Aharonov-Bohm oscillations in the total conductance. Neglecting the contribution of self-crossing resonant-percolation trajectories, we found that the inter-edge carrier transport is similar to propagation in one-dimensional system with off-diagonal disorder. Then we demonstrated that each Landau band has an extended state Ε Ν , while all other states are localized, and the localization length behaves as L - 1 Ν (Ε) ∼ (Ε - Ε Ν ) 2 . (author)

Secure Communications with Mobile Devices During In-Field Activities

International Nuclear Information System (INIS)

Partee, M.S.; Moser, F.

2015-01-01

One of the classic problems in information security is how to exchange confidential information securely in uncontrolled environments. There have been innumerable academic and commercial hours spent resolving this question. In traditional practice, securing communications meant investing in satellites, specialized hardware, rigorous security engineering and testing, and expending a lot of resources. For this reason, smaller organizations have often been unable to secure communications. The widespread adoption of mobile communications and the modern mobile device has brought about unprecedented abilities to stay connected with colleagues during work activities. As connectedness has increased, so have the opportunities for information compromise. The enormous mobile landscape, with competing ecosystems, large research and product development budgets, proliferating devices, and rapidly-shifting technical foundations prove to be a tremendous source of both opportunity and risk. With the reality of shrinking budgets and increasing threats, many organizations, commercial enterprises, and product vendors are looking for new ways to utilize existing resources for secure communications and mobile work capabilities. Keeping communications private and secure using the infrastructure of the world's telecommunications network and standard computing and mobile devices is the challenge. This paper will examine some methods for communicating securely using consumer mobile products and evaluate the risk such tools can present to an organization in the context of inspection work in the field. (author)

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

Science.gov (United States)

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.

Development of chromatographic methods for the determination of genotoxic impurities in cloperastine fendizoate.

Science.gov (United States)

García, Antonia; Rupérez, Francisco J; Ceppa, Florencia; Pellati, Federica; Barbas, Coral

2012-03-05

The classification of an impurity of a drug substance as genotoxic means that the "threshold of toxicological concern" (TTC) value of 1.5 μg/day intake, considered to be associated with an acceptable risk, should be the admissible limit in the raw material and that leads to new analytical challenges. In this study, reliable chromatographic methods were developed and applied as limit tests for the control of three genotoxic impurities (GTIs) in cloperastine fendizoate, drug widely used as an antitussive active pharmaceutical ingredient (API). In particular, GC-MS was applied to the determination of one alkyl halide (2-chloroethanol, 2-CE), while HPLC-DAD was selected for the analysis of two sulfonate esters (methyl p-toluenesulfonate, MPTS, and 2-chloroethyl p-toluenesulfonate, CEPTS). Regarding GC-MS, strong anion-exchange (SAX)-SPE was applied to remove fendizoate from the sample solutions, due its low volatility and its high amount in the raw material. The GC-MS analysis was performed on a Factor Four VF-23 ms capillary column (30 m × 0.25 mm I.D., film thickness 0.25 μm, Varian). Single ion-monitoring (SIM) detection mode was set at m/z 80. In the case of HPLC-DAD, a suitable optimization of the chromatographic conditions was carried out in order to obtain a good separation of the impurity peaks from the drug substance peaks. The optimized method utilizes a SymmetryShield RP(8) column (250 mm × 4.6 mm, 5 μm, Waters) kept at 50°C, with phosphate buffer (pH 3.0; 10 mM)-methanol (containing 10% ACN) (45:55, v/v) as the mobile phase, at the flow-rate of 1.7 mL/min and UV detection at 227 nm. The required sensitivity level was achieved by injecting 80 μL of sample solution, purified from fendizoate by SAX-SPE, followed by a 1:1 (v/v) dilution of the SPE eluate with water. For both GC-MS and HPLC-DAD, the method validation was performed in relation to specificity and limit of detection (LOD), as required by ICH guidelines in relation to limit assays. The

Impurity strength and impurity domain modulated frequency-dependent linear and second non-linear response properties of doped quantum dots

Energy Technology Data Exchange (ETDEWEB)

Datta, Nirmal Kumar [Department of Physics, Suri Vidyasagar College, Suri, Birbhum 731 101, West Bengal (India); Ghosh, Manas [Department of Chemistry, Physical Chemistry Section, Visva Bharati University, Santiniketan, Birbhum 731 235, West Bengal (India)

2011-08-15

We explore the pattern of frequency-dependent linear and second non-linear optical responses of repulsive impurity doped quantum dots harmonically confined in two dimensions. The dopant impurity potential chosen assumes a Gaussian form and it is doped into an on-center location. The quantum dot is subject to a periodically oscillating external electric field. For some fixed values of transverse magnetic field strength ({omega}{sub c}) and harmonic confinement potential ({omega}{sub 0}), the influence of impurity strength (V{sub 0}) and impurity domain ({xi}) on the diagonal components of the frequency-dependent linear ({alpha}{sub xx} and {alpha}{sub yy}) and second non-linear ({gamma}{sub xxxx} and {gamma}{sub yyyy}) responses of the dot are computed through a linear variational route. The investigations reveal that the optical responses undergo enhancement with increase in both V{sub 0} and {xi} values. However, in the limitingly small dopant strength regime one observes a drop in the optical responses with increase in V{sub 0}. A time-average rate of energy transfer to the system is often invoked to support the findings. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Boron, nitrogen, and nickel impurities in GeC nanoribbons: A first-principles investigation

Energy Technology Data Exchange (ETDEWEB)

Xu, Zhuo; Li, Yangping, E-mail: liyp@nwpu.edu.cn; Liu, Zhengtang

2017-07-01

Highlights: • The impurities preferentially substitutes the Ge atom at the ribbon edge. • The impurities could result in a reduction of the band gap of 7-AGeCNR. • The impurities turns the metallic behavior of 4-ZGeCNR into semiconductor. • The impurities could change the magnetic moment of 4-ZGeCNR. • The impurities could introduce magnetic moments into the non-magnetic 7-AGeCNR. - Abstract: Using first-principles calculations based on the density functional theory we investigated the structural, electronic and magnetic properties of substitutional boron, nitrogen, and nickel impurities in germanium carbide (GeC) nanoribbons. Hydrogen terminated GeC ribbons with armchair and zigzag edges are considered here. We observed that all three impurities preferentially substitutes the Ge atom at the ribbon edge. In addition, the electronic band structures of the doped systems indicate that (i) the impurities could introduce impurity bands in the band gap and resulting in a reduction of the band gap of 7-AGeCNR, (ii) the metallic behavior of 4-ZGeCNR turns into semiconductor because of the incorporation of the impurities, (iii) the impurities could change the magnetic moment of 4-ZGeCNR and even introduce magnetic moment into the non-magnetic 7-AGeCNR.

Identification and Structural Characterization of Unidentified Impurity in Bisoprolol Film-Coated Tablets

Directory of Open Access Journals (Sweden)

Ivana Mitrevska

2017-01-01

Full Text Available The aim of this study is the identification, structural characterization, and qualification of a degradation impurity of bisoprolol labeled as Impurity RRT 0.95. This degradation product is considered as a principal thermal degradation impurity identified in bisoprolol film-coated tablets. The impurity has been observed in the stress thermal degradation study of the drug product. Using HPLC/DAD/ESI-MS method, a tentative structure was assigned and afterwards confirmed by detailed structural characterization using NMR spectroscopy. The structure of the target Impurity RRT 0.95 was elucidated as phosphomonoester of bisoprolol, having relative molecular mass of 406 (positive ionization mode. The structural characterization was followed by qualification of Impurity RRT 0.95 using several different in silico methodologies. From the results obtained, it can be concluded that no new structural alerts have been generated for Impurity RRT 0.95 relative to the parent compound bisoprolol. The current study presents an in-depth analysis of the full characterization and qualification of an unidentified impurity in a drug product with the purpose of properly defining the quality specification of the product.

Characterization of intermittency of impurity turbulent transport in tokamak edge plasmas

International Nuclear Information System (INIS)

Futatani, S.; Benkadda, S.; Nakamura, Y.; Kondo, K.

2008-01-01

The statistical properties of impurity transport of a tokamak edge plasma embedded in a dissipative drift-wave turbulence are investigated using structure function analysis. The impurities are considered as a passive scalar advected by the plasma flow. Two cases of impurity advection are studied and compared: A decaying impurities case (given by a diffusion-advection equation) and a driven case (forced by a mean scalar gradient). The use of extended self-similarity enables us to show that the relative scaling exponent of structure functions of impurity density and vorticity exhibit similar multifractal scaling in the decaying case and follows the She-Leveque model. However, this property is invalidated for the impurity driven advection case. For both cases, potential fluctuations are self-similar and exhibit a monofractal scaling in agreement with Kolmogorov-Kraichnan theory for two-dimensional turbulence. These results obtained with a passive scalar model agree also with test-particle simulations.

Associations of children's independent mobility and active travel with physical activity, sedentary behaviour and weight status: a systematic review.

Science.gov (United States)

Schoeppe, Stephanie; Duncan, Mitch J; Badland, Hannah; Oliver, Melody; Curtis, Carey

2013-07-01

Health benefits from children's independent mobility and active travel beyond school travel are largely unexplored. This review synthesized the evidence for associations of independent mobility and active travel to various destinations with physical activity, sedentary behaviour and weight status. Systematic review. A systematic search in six databases (PubMed, Scopus, CINAHL, SportDiscus, PsychInfo, TRIS) for papers published between January 1990 and March 2012 was undertaken, focussing on children aged 3-18 years. Study inclusion and methodological quality were independently assessed by two reviewers. 52 studies were included. Most studies focussed solely on active travel to and/or from school, and showed significant positive associations with physical activity. The same relationship was detected for active travel to leisure-related places and independent mobility with physical activity. An inverse relationship between active travel to school and weight status was evident but findings were inconsistent. Few studies examined correlations between active travel to school and self-reported screen-time or objectively measured sedentary behaviour, and findings were unclear. Studies on independent mobility suggested that children who have the freedom to play outdoors and travel actively without adult supervision accumulate more physical activity than those who do not. Further investigation of children's active travel to leisure-related destinations, measurement of diverse sedentary behaviour beyond simply screen-based activities, and consistent thresholds for objectively measured sedentary behaviour in children will clarify the inconsistent evidence base on associations of active travel with sedentary behaviour and weight status. Copyright © 2012 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Negative compressibility observed in graphene containing resonant impurities

International Nuclear Information System (INIS)

Chen, X. L.; Wang, L.; Li, W.; Wang, Y.; He, Y. H.; Wu, Z. F.; Han, Y.; Zhang, M. W.; Xiong, W.; Wang, N.

2013-01-01

We observed negative compressibility in monolayer graphene containing resonant impurities under different magnetic fields. Hydrogenous impurities were introduced into graphene by electron beam (e-beam) irradiation. Resonant states located in the energy region of ±0.04 eV around the charge neutrality point were probed in e-beam-irradiated graphene capacitors. Theoretical results based on tight-binding and Lifshitz models agreed well with experimental observations of graphene containing a low concentration of resonant impurities. The interaction between resonant states and Landau levels was detected by varying the applied magnetic field. The interaction mechanisms and enhancement of the negative compressibility in disordered graphene are discussed.

Modeling of impurity transport in the core plasma

International Nuclear Information System (INIS)

Hulse, R.A.

1992-01-01

This paper presents a brief overview of computer modeling of impurity transport in the core region of controlled thermonuclear fusion plasmas. The atomic processes of importance in these high temperature plasmas and the numerical formulation of the model are described. Selected modeling examples are then used to highlight some features of the physics of impurity behavior in large tokamak fusion devices, with an emphasis on demonstrating the sensitivity of such modeling to uncertainties in the rate coefficients used for the atomic processes. This leads to a discussion of current requirements and opportunities for generating the improved sets of comprehensive atomic data needed to support present and future fusion impurity modeling studies

Electronic structure of deep impurity centers in silicon

International Nuclear Information System (INIS)

Oosten, A.B. van.

1989-01-01

This thesis reports an experimental study of deep level impurity centers in silicon, with much attention for theoretical interpretation of the data. A detailed picture of the electronic structure of several centers was obtained by magnetic resonance techniques, such as electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR) and field scanned ENDOR (FSE). The thesis consists of two parts. The first part deals with chalcogen (sulfur, selenium and tellurium) related impurities, which are mostly double donors. The second part is about late transition metal (nickel, palladium and platinum) impurities, which are single (Pd,Pt) or double (Ni) acceptor centers. (author). 155 refs.; 51 figs.; 23 tabs

An Implant-Passivated Blocked Impurity Band Germanium Detector for the Far Infrared, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — We propose to fabricate a germanium blocked-impurity-band (BIB) detector using a novel process which will enable us to: 1- fabricate a suitably-doped active layer...

Research in Hydrogen Passivation of Defects and Impurities in Silicon: Final Report, 2 May 2000-2 July 2003

International Nuclear Information System (INIS)

Ashok, S.

2004-01-01

This subcontract report describes hydrogenating Si samples by different methods such as low-energy implantation, electron cyclotron resonance (ECR) plasma, and thermal diffusion. The samples were provided through NREL. The experimental work, carried out at Penn State, involved the study of hydrogen interaction with defects, trapping, migration, and formation of complexes. The principal vehicle for the latter study was ion implantation, and the intent to understand mechanisms of defect passivation and activation by hydrogen. NREL implemented a study of hydrogen passivation of impurities and defects in silicon solar cells. The work included theoretical and experimental components performed at different universities. The theoretical studies consisted of the calculation of the structure and parameters related to hydrogen diffusion and interactions of hydrogen with transition-metal impurities in silicon. Experimental studies involved measurements of hydrogen and hydrogen-impurity complexes, and diffusion properties of various species of hydrogen in Si. The experimental work at Penn State included introduction of hydrogen in a variety of PV Si by ECR plasma, low-energy ion implantation, and thermal diffusion. The specific tasks were the evaluation of hydrogen interaction with defects engineered by ion implantation; defect passivation, activation, and migration in hydrogenated Si under thermal anneal; and electrical activity of hydrogen-impurity complexes. Electrical characterization entailed I-V and C-V measurements, spreading resistance, and deep-level transient spectroscopy (DLTS)

Tokamak impurity-control techniques

International Nuclear Information System (INIS)

Schmidt, J.A.

1980-01-01

A brief review is given of the impurity-control functions in tokamaks, their relative merits and disadvantages and some prominent edge-interaction-control techniques, and there is a discussion of a new proposal, the particle scraper, and its potential advantages. (author)

Atomic spectroscopy on fusion relevant ions and studies of light impurities in the JET tokamak

International Nuclear Information System (INIS)

Tunklev, M.

1999-03-01

The spectrum and energy levels of C IV and the 3l-4l system of the Mg-like ions in the iron group elements have been investigated. This has led to several hundred identified transitions, many of them previously unknown. Using the Charge Exchange Diagnostic system at JET, ion temperatures, rotation velocities and densities have been derived from visible spectroscopic measurements on fully ionised light impurities, such as He, C, N and Ne. The existence of plume contribution from beam produced hydrogen-like ions has been proven beyond any doubt to affect the deduction of the active charge exchange signal of He II. In the case of C VI the plume signal was estimated to be at least a factor of five lower than the active charge exchange signal. Line integrated passive charge exchange emission between neutral background atoms and fully stripped impurity ions has been investigated and modelled. When the synthetic spectrum is fitted into the experimentally detected spectra the neutral background density can be deduced. The importance of including background atoms (H, D and T) as charge exchange donors, not only in state 2s, but also in state 1s, has shown to be crucial in high temperature shots. Transport of light impurities has been studied with gas puff injections into steady state H-mode plasmas. The results suggest that light impurities are transported as described by the neo-classical Pfirsch-Schlueter regime at the edge, whilst in the centre, sawtoothing, preferably to Banana transport, is mixing the plasma and increases the measured values on the diffusion. For the peaking of impurities in a steady state plasma an anomalous treatment was more in agreement with the experimental data. Certain confinement information, previously predicted theoretically as a part of the peaking equation, has been experimentally verified

Sodium sampling and impurities determination

International Nuclear Information System (INIS)

Docekal, J.; Kovar, C.; Stuchlik, S.

1980-01-01

Samples may be obtained from tubes in-built in the sodium facility and further processed or they are taken into crucibles, stored and processed later. Another sampling method is a method involving vacuum distillation of sodium, thus concentrating impurities. Oxygen is determined by malgamation, distillation or vanadium balance methods. Hydrogen is determined by the metal diaphragm extraction, direct extraction or amalgamation methods. Carbon is determined using dry techniques involving burning a sodium sample at 1100 degC or using wet techniques by dissolving the sample with an acid. Trace amounts of metal impurities are determined after dissolving sodium in ethanol. The trace metals are concentrated and sodium excess is removed. (M.S.)

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.

Science.gov (United States)

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.

Influence of the impurity-defect and impurity-impurity interactions on the crystalline silicon solar cells conversion efficiency; Influence des interactions impurete-defaut et impurete-impurete sur le rendement de conversion des cellules photovoltaiques au silicium cristallin

Energy Technology Data Exchange (ETDEWEB)

Dubois, S

2007-05-15

This study aims at understanding the influence of the impurity - defect interaction on the silicon solar cell performances. We studied first the case of single-crystalline silicon. We combined numerical simulations and experimental data providing new knowledge concerning metal impurities in silicon, to quantify the evolution of the conversion efficiency with the impurity concentration. Mainly due to the gettering effects, iron appears to be quite well tolerated. It is not the case for gold, diffusing too slowly. Hydrogenation effects were limited. We transposed then this study toward multi-crystalline silicon. Iron seems rather well tolerated, due to the gettering effects but also due to the efficiency of the hydrogenation. When slow diffusers are present, multi crystalline silicon is sensitive to thermal degradation. n-type silicon could solve this problem, this material being less sensitive to metal impurities. (author)

Impurity states in two - and three-dimensional disordered systems

International Nuclear Information System (INIS)

Silva, A.F. da; Fabbri, M.

1984-01-01

We investigate the microscopic structure of the impurity states in two-and three-dimensional (2D and 3d) disordered systems. A cluster model is outlined for the donor impurity density of states (DIDS) of doped semiconductors. It is shown that the impurity states are very sensitive to a change in the dimensionality of the system, i.e from 3D to 2D system. It is found that all eigenstates become localized in 2D disordered system for a large range of concentration. (Author) [pt

Extraction process for removing metallic impurities from alkalide metals

Science.gov (United States)

Royer, Lamar T.

1988-01-01

A development is described for removing metallic impurities from alkali metals by employing an extraction process wherein the metallic impurities are extracted from a molten alkali metal into molten lithium metal due to the immiscibility of the alkali metals in lithium and the miscibility of the metallic contaminants or impurities in the lithium. The purified alkali metal may be readily separated from the contaminant-containing lithium metal by simple decanting due to the differences in densities and melting temperatures of the alkali metals as compared to lithium.

Impurity states in two-and three-dimensional disordered systems

International Nuclear Information System (INIS)

Silva, A.F. da; Fabbri, M.

1984-04-01

The microscopic structure of the impurity states in two-and three-dimensional (2D and 3D) disordered systems is investigated. A cluster model is outlined for the donor impurity density of states (DIDS) of doped semiconductors. It is shown that the impurity states are very sensitive to a change in the dimensionality of the system, i.e., from 3D to 2D system. It is found that all eigenstates become localized in 2D disordered system for a large range of concentration. (Author) [pt

Effect of HEH[EHP] impurities on the ALSEP solvent extraction process

Energy Technology Data Exchange (ETDEWEB)

Holfeltz, Vanessa E. [Nuclear Chemistry and Engineering Group, Pacific Northwest National Laboratory, Richland, WA, USA; School of Nuclear Science and Engineering, Oregon State University, Corvallis, OR, USA; Campbell, Emily L. [Nuclear Chemistry and Engineering Group, Pacific Northwest National Laboratory, Richland, WA, USA; Peterman, Dean R. [Aqueous Separations and Radiochemistry Department, Idaho National Laboratory, Idaho Falls, ID, USA; Standaert, Robert F. [Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA; Department of Biochemistry & amp, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, USA; Biology & amp, Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA; Shull Wollan Center — a Joint Institute for Neutron Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA; Paulenova, Alena [School of Nuclear Science and Engineering, Oregon State University, Corvallis, OR, USA; Lumetta, Gregg J. [Nuclear Chemistry and Engineering Group, Pacific Northwest National Laboratory, Richland, WA, USA; Levitskaia, Tatiana G. [Nuclear Chemistry and Engineering Group, Pacific Northwest National Laboratory, Richland, WA, USA

2017-12-20

In solvent extraction processes, organic phase impurities can negatively impact separation factors, hydrolytic performance, and overall system robustness. This affects the process-level viability of a separation concept and necessitates knowledge of the behavior and mechanisms to control impurities in the solvent. The most widespread way through which impurities are introduced into a system is through impure extractants and/or diluents used to prepare the solvent, and often development of new purification schemes to achieve the desired level of purity is needed. In this work, the acidic extractant, 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP])—proposed for application in extractive processes aimed at separating trivalent minor actinides from lanthanides and other fission products—is characterized with respect to its common impurities and their impact on Am(III) stripping in the Actinide Lanthanide SEParation (ALSEP) system. To control impurities in HEH[EHP], existing purification technologies commonly applied for the acidic organophosphorus reagents are reviewed, and a new method specific to HEH[EHP] purification is presented.

Tight-Binding Description of Impurity States in Semiconductors

Science.gov (United States)

Dominguez-Adame, F.

2012-01-01

Introductory textbooks in solid state physics usually present the hydrogenic impurity model to calculate the energy of carriers bound to donors or acceptors in semiconductors. This model treats the pure semiconductor as a homogeneous medium and the impurity is represented as a fixed point charge. This approach is only valid for shallow impurities…

Gate-modulated conductance of few-layer WSe2 field-effect transistors in the subgap regime: Schottky barrier transistor and subgap impurity states

International Nuclear Information System (INIS)

Wang, Junjie; Feng, Simin; Rhodes, Daniel; Balicas, Luis; Nguyen, Minh An T.; Watanabe, K.; Taniguchi, T.; Mallouk, Thomas E.; Terrones, Mauricio; Zhu, J.

2015-01-01

Two key subjects stand out in the pursuit of semiconductor research: material quality and contact technology. The fledging field of atomically thin transition metal dichalcogenides (TMDCs) faces a number of challenges in both efforts. This work attempts to establish a connection between the two by examining the gate-dependent conductance of few-layer (1-5L) WSe 2 field effect devices. Measurements and modeling of the subgap regime reveal Schottky barrier transistor behavior. We show that transmission through the contact barrier is dominated by thermionic field emission (TFE) at room temperature, despite the lack of intentional doping. The TFE process arises due to a large number of subgap impurity states, the presence of which also leads to high mobility edge carrier densities. The density of states of such impurity states is self-consistently determined to be approximately 1–2 × 10 13 /cm 2 /eV in our devices. We demonstrate that substrate is unlikely to be a major source of the impurity states and suspect that lattice defects within the material itself are primarily responsible. Our experiments provide key information to advance the quality and understanding of TMDC materials and electrical devices

BWR water chemistry impurity studies

International Nuclear Information System (INIS)

Ljungberg, L.G.; Korhonen, S.; Renstroem, K.; Hofling, C.G.; Rebensdorff, B.

1990-03-01

Laboratory studies were made on the effect of water impurities on environmental cracking in simulated BWR water of stainless steel, low alloy steel and nickel-base alloys. Constant elongation rate tensile (CERT) tests were run in simulated normal water chemistry (NWC), hydrogen water chemistry (HWC), or start-up environment. Sulfate, chloride and copper with chloride added to the water at levels of a fraction of a ppM were found to be extremely deleterious to all kinds of materials except Type 316 NG. Other detrimental impurities were fluoride, silica and some organic acids, although acetic acid was beneficial. Nitrate and carbon dioxide were fairly inoccuous. Corrosion fatigue and constant load tests on compact tension specimens were run in simulated normal BWR water chemistry (NWC) or hydrogen water chemistry (HWC), without impurities or with added sulfate or carbon dioxide. For sensitized Type 304 SS in NWC, 0.1 ppM sulfate increased crack propagation rates in constant load tests by up to a factor of 100, and in fatigue tests up to a factor of 10. Also, cracking in Type 316 nuclear grade SS and Alloy 600 was enhanced, but to a smaller degree. Carbon dioxide was less detrimental than sulfate. 3 figs., 4 tabs

Human brain wave activity during exposure to radiofrequency field emissions from mobile phones

International Nuclear Information System (INIS)

D'Costa, H.; Cosic, I.

2003-01-01

The aim of this study was to determine whether there is an effect of mobile phone electromagnetic field emissions on the human electroencephalograph (EEG). EEG recordings from ten awake subjects were taken during exposure to radiofrequency (RF) emissions from a mobile phone positioned behind the head. Two experimental trials were conducted. In the first trial, RF exposures were generated by a GSM mobile phone with the speaker disabled and configured to transmit at full-radiated power. During the second trial, exposures were generated by a non-modified GSM mobile phone in active standby mode. For each trial, subjects were exposed in five minute intervals to a randomized, interrupted sequence of five active and five sham exposures. The experiment was conducted under single-blind conditions. The average EEG band power in active exposure recordings was compared to corresponding sham recordings. Statistical tests indicated significant difference in the full-power mode trial within the EEG alpha (8-13 Hz) and beta (13-32 Hz) bands. A subsequent statistical analysis of median spectral power in discrete EEG rhythms revealed significant differences in 7 of the 32 distinct frequencies overall. In conclusion, the results of this study lend support to EEG effects from mobile phones activated in talk-mode. Copyright (2003) Australasian College of Physical Scientists and Engineers in Medicine

STM tunneling through a quantum wire with a side-attached impurity

International Nuclear Information System (INIS)

Kwapinski, T.; Krawiec, M.; Jalochowski, M.

2008-01-01

The STM tunneling through a quantum wire (QW) with a side-attached impurity (atom, island) is investigated using a tight-binding model and the non-equilibrium Keldysh Green function method. The impurity can be coupled to one or more QW atoms. The presence of the impurity strongly modifies the local density of states of the wire atoms, thus influences the STM tunneling through all the wire atoms. The transport properties of the impurity itself are also investigated mainly as a function of the wire length and the way it is coupled to the wire. It is shown that the properties of the impurity itself and the way it is coupled to the wire strongly influence the STM tunneling, the density of states and differential conductance

Effects of impurities on crystal growth in fructose crystallization

Science.gov (United States)

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.

Spectroscopic Measurements of Impurity Spectra on the EAST Tokamak

International Nuclear Information System (INIS)

Fu Jia; Li Yingying; Shi Yuejiang; Wang Fudi; Zhang Wei; Lv Bo; Huang Juan; Wan Baonian; Zhou Qian

2012-01-01

Ultraviolet (UV) and visible impurity spectra (200∼750 nm) are commonly used to study plasma and wall interactions in magnetic fusion plasmas. Two optical multi-channel analysis (OMA) systems have been installed for the UV-visible spectrum measurement on EAST. These two OMA systems are both equipped with the Czerny-Turner (C-T) type spectrometer. The upper vacuum vessel and inner divertor baffle can be viewed simultaneously through two optical lenses. The OMA1 system is mainly used for multi-impurity lines radiation measurement. A 280 nm wavelength range can be covered by a 300 mm focal length spectrometer equipped with a 300 grooves/mm grating. The Dα/Hα line shapes can be resolved by the OMA2 system. The focal length is 750 mm. The spectral resolution can be up to 0.01 nm using a 1800 grooves/mm grating. The impurity behaviour and hydrogen ratio evolution after boroniztion, lithium coating, and siliconization are compared. Lithium coating has shown beneficial effects on the reduction of edge recycling and low Z impurity (C, O) influx. The impurity expelling effect of the divertor configuration is also briefly discussed through multi-channels observation of OMA1 system. (magnetically confined plasma)

Properties of magnetic impurities embedded into an anisotropic Heisenberg chain with spin gap

International Nuclear Information System (INIS)

Schlottmann, P.

2000-01-01

We consider a U(1)-invariant model consisting of the integrable anisotropic easy-axis Heisenberg chain of arbitrary spin S embedding an impurity of spin S'. The host chain has a spin gap for all values of S. The ground state properties and the elementary excitations of the host are studied as a function of the anisotropy and the magnetic field. The impurity is located on a link of the chain and interacts only with both neighboring sites. The coupling of the impurity to the lattice can be tuned by the impurity rapidity p 0 (usually playing the role of the Kondo coupling). The impurity model is then integrable as a function of two continuous parameters (the anisotropy and the impurity rapidity) and two discrete variables (the spins S and S'). The Bethe ansatz equations are derived and used to obtain the magnetization of the impurity. The impurity magnetization is non-universal as a function of p 0 . For small fields the impurity magnetization is determined by the spin gap and the van Hove singularity of the rapidity band. For an overcompensated impurity (S'< S) at intermediate fields there is a crossover to non-Fermi-liquid behavior remnant from the suppressed quantum critical point

Impurity production and transport at the JET belt limiter

International Nuclear Information System (INIS)

Pitcher, C.S.; McCracken, G.M.; Strangeby, P.C.; Toronto Univ., ON; Summers, D.D.R.

1989-01-01

Under certain operating conditions in JET the impurity content of the discharge can be high, thus reducing the fusion reaction rate through the dilution of the hydrogenic fuel. The dilution in most discharges is predominantly due to carbon impurities. In order to understand how carbon impurities are produced and transported into the plasma, detailed measurements with interference filters centered on intense spectral lines of the low ionization states of carbon (C I, C II, C III) as well as the fuel species (Dα) and helium (He I). (author) 6 refs., 4 figs

Hopping conductivity via deep impurity states in InP

International Nuclear Information System (INIS)

Kuznetsov, V.P.; Messerer, M.A.; Omel'yanovskij, Eh.M.

1984-01-01

Hopping (epsilon 3 ) and Mott conductivities via deep impurity compounds with localization radius below 10 A have been studied using as an example Mn in InP. It is shown, that the existing theory of hopping conductivity in low-alloyed semiconductors with Na 3 << 1 can be Used for the case of deep centres as successfully as for the case of insignificant hydrogen-like impurities. Fundamental parameters of the theory: localization radius of wave function of deep impurities, state density near the Fermi level, mean hop length, are determined

Behavior of arsenic impurity at antimony electric precipitation

International Nuclear Information System (INIS)

Kim, G.N.; Rakhmanov, A.

2001-01-01

In the paper the arsenic impurity electrochemical behavior and it purification from antimony by electric precipitation out of fluoride solutions was studied. For this the arsenic sample with mass 0.003-0.006 g has been irradiated at the WWR-SM nuclear reactor during 3-5 hour in the thermal neutron flux 10 13 n/cm 2 s, after 24 h keeping the sample has being dissolved in the concentrated nitric acid, and then it has been evaporated several times with distillation water addition up to wet precipitation state. It is shown, that arsenic impurity behavior character in the antimony electric precipitation out to fluoride electrolyte depends on the electrolyte content, electrolysis conditions, arsenic valency state in arsenic impurity existence in the five-valency state its joint electric reduction with antimony is practically not observing. In the case the arsenic being in three-valency state, it joint electric reduction with antimony is taking place. In this time the electrolytic antimony contents arsenic impurities less in dozen time than initial material

Quenching of overcompensated Kondo impurities via channel asymmetry

International Nuclear Information System (INIS)

Schlottmann, P.; Lee, K.

1996-01-01

We consider a spin-1/2 impurity interacting with conduction electrons in two different orbital channels via an isotropic spin exchange. The exchange is the same for both channels, but a crystalline field breaks the symmetry between the orbital channels. This corresponds to a splitting of the conduction electron Γ 8 into two doublets in the quadrupolar Kondo effect and to the application of an external magnetic field in the electron assisted tunneling of an atom in a double-well potential. We study the ground-state properties of the impurity as a function of the magnetic and crystalline fields. The crystalline field quenches the critical behavior of the overcompensated fixed point: The impurity ground state is a singlet. (orig.)

A one-dimensional plasma and impurity transport model for reversed field pinches

International Nuclear Information System (INIS)

Veerasingam, R.

1991-11-01

In this thesis a one-dimensional (1-D) plasma and impurity transport model is developed to address issues related to impurity behavior in Reversed Field Pinch (RFP) fusion plasmas. A coronal non-equilibrium model is used for impurities. The impurity model is incorporated into an existing one dimensional plasma transport model creating a multi-species plasma transport model which treats the plasma and impurity evolution self-consistently. Neutral deuterium particles are treated using a one-dimensional (slab) model of neutral transport. The resulting mode, RFPBI, is then applied to existing RFP devices such as ZT-40M and MST, and also to examine steady state behavior of ZTH based on the design parameters. A parallel algorithm for the impurity transport equations is implemented and tested to determine speedup and efficiency

Computers in the investigation of the impurity content of high-purity materials

International Nuclear Information System (INIS)

Makarov, Yu.B.; Yan'kov, S.V.

1987-01-01

The efficiency of the concept of data banks for the accumulation and processing of information is now generally acknowledged. In scientific investigations not only bibliographic but also factual data banks are becoming more and more prevalent. In this article, the authors consider the possibilities of providing a data bank on high-purity materials for the study of impurity contents. Also in this paper, the authors distinguish the following groups of problems that arise in the study of impurity composition and presents examples of their proposed solutions to these problems: the analysis of error and the determination of the most probably value of impurity concentration; the estimation of average properties of impurity composition with respect to groups of impurities and samples, and the forecast of the complete impurity composition

Impurity binding energy for δ-doped quantum well structures

Indian Academy of Sciences (India)

Administrator

Calculations are made for the case of not so big impurity concentrations, when impurity bands are not .... Blom et al (2003), but our data correspond qualitatively to Bastard's .... 0113U000612 and by Ukrainian Ministry of Education and Science ...

Summary of IAEA technical committee meeting on impurity control

International Nuclear Information System (INIS)

Itoh, Kimitaka.

1989-03-01

Presentations given in the IAEA technical committee meeting on impurity control (held in JAERI from 13 to 15 February, 1989) are summarized, putting the emphasis on the physics modelling of the plasma related to the impurity production and confinement. (author)

Purification of simple substances by distillation with impurity hydrothermal oxidation

International Nuclear Information System (INIS)

Kalashnik, O.N.; Nisel'son, L.A.

1987-01-01

A possibility of applying distillation method in water vapours for purification of simple substances from impurities is studied. Based on thermodynamic analysis of interaction processes in E-H 2 O system, conducted using a computer, it is as certained that SS, Se, Te, As, Cd, Hg can be purified from the majority of the impurities analysed by distillation in a water vapour flow. Behaviour of Zn, C, Ge, Al, Sb characteristic impurities under cadmium, arsenic and tellurium distillation is studied. Experiments on cadmium, arsenic and tellurium purification have confirmed, that distillation with hydrothermal oxidation of Zn, C, Ge impurities sometimes appears to be a more effective method as compared to distillation in a hydrogen flow

The effect of impurities on the electronic properties of MgO

Energy Technology Data Exchange (ETDEWEB)

Jalili, Seifollah [Department of Chemistry, K.N. Toosi University of Technology, P.O. Box 16315-1618, Tehran (Iran, Islamic Republic of); Computational Physical Sciences Research Laboratory, Department of Nano-Science, Institute for Studies in Theoretical Physics and Mathematics (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)], E-mail: sjalili@nano.ipm.ac.ir; Majidi, Roya [Department of Physics, Shahid Beheshti University, Tehran (Iran, Islamic Republic of)

2008-10-01

The effect of impurities on the electronic properties of MgO is investigated using the full potential linearized augmented plane-wave plus local-orbitals method based on density functional theory. The electronic band structures and density of states of MgO in the presence of Ca, Li, and Na impurities were calculated. It is found that increasing the amount of Ca impurity decreases the energy band gap and increases the width of the upper part of the valence band. Some of the considered impurities (Li and Na) change the electronic properties of MgO extensively.

The effect of impurities on the electronic properties of MgO

International Nuclear Information System (INIS)

Jalili, Seifollah; Majidi, Roya

2008-01-01

The effect of impurities on the electronic properties of MgO is investigated using the full potential linearized augmented plane-wave plus local-orbitals method based on density functional theory. The electronic band structures and density of states of MgO in the presence of Ca, Li, and Na impurities were calculated. It is found that increasing the amount of Ca impurity decreases the energy band gap and increases the width of the upper part of the valence band. Some of the considered impurities (Li and Na) change the electronic properties of MgO extensively

Impurity sublattice localization in ZnO revealed by li marker diffusion

DEFF Research Database (Denmark)

Azarov, A.Yu.; Knutsen, K.E.; Neuvonen, P.T.

2013-01-01

Sublattice localization of impurities in compound semiconductors, e.g., ZnO, determines their electronic and optical action. Despite that the impurity position may be envisaged based on charge considerations, the actual localization is often unknown, limiting our understanding of the incorporation...... and possible doping mechanisms. In this study, we demonstrate that the preferential sublattice occupation for a number of impurities in ZnO can be revealed by monitoring Li diffusion. In particular, using ion implantation, the impurity incorporation into the Zn sublattice (holds for, B, Mg, P, Ag, Cd, and Sb...

Device for separating, purifying and recovering nuclear fuel material, impurities and materials from impurity-containing nuclear fuel materials or nuclear fuel containing material

International Nuclear Information System (INIS)

Sato, Ryuichi; Kamei, Yoshinobu; Watanabe, Tsuneo; Tanaka, Shigeru.

1988-01-01

Purpose: To separate, purify and recover nuclear fuel materials, impurities and materials with no formation of liquid wastes. Constitution: Oxidizing atmosphere gases are introduced from both ends of a heating furnace. Vessels containing impurity-containing nuclear fuel substances or nuclear fuel substance-containing material are continuously disposed movably from one end to the other of the heating furnace. Then, impurity oxides or material oxides selectively evaporated from the impurity-containing nuclear fuel substances or nuclear fuel substance-containing materials are entrained in the oxidizing atmosphere gas and the gases are led out externally from a discharge port opened at the intermediate portion of the heating furnace, filters are disposed to the exit to solidify and capture the nuclear fuel substances and traps are disposed behind the filters to solidify and capture the oxides by spontaneous air cooling or water cooling. (Sekiya, K.)

Helium impurities in a PNP-primary coolant circuit

International Nuclear Information System (INIS)

Reif, M.

1981-01-01

The concentration of impurities to be expected have been defined in consideration of recent findings concerning the rates of infiltration and formation and the reaction mechanisms of the impurity components in the circuit. The data obtained correspond with the requirements on the metallic high-temperature components as well as with the requirements of limited graphite corrosion. (DG) [de

Determining factors for the presence of impurities in selectively collected biowaste.

Science.gov (United States)

Puig-Ventosa, Ignasi; Freire-González, Jaume; Jofra-Sora, Marta

2013-05-01

The presence of impurities in biodegradable waste (biowaste) causes problems with the management of waste, among which are additional costs derived from the need to improve pre-treatment of biowaste, loss of treatment capacity and the difficulty selling treated biowaste as compost owing to its low quality. When treated biowaste is used for soil conditioning it can also cause soil pollution. Understanding the reasons why impurities are in biowaste and the factors affecting the percentage of impurities present can be used to determine ways to minimise these negative effects. This article attempts to identify the main causes for the presence of impurities in biowaste. In order to do so, it carries out an empirical analysis of the level of impurities in biowaste from municipal waste collection in two steps. First, a bivariate analysis focuses on significant correlations between the presence of impurities and several variables. Second, the construction of an explanatory model based on the significant relations obtained in the first step, and on literature research, are used to check the stated hypothesis. The estimates demonstrate that the collection system, the global levels of separate collection, the urban density of the municipality and the requirement to use compostable bags may be the main drivers of impurity levels in biowaste.

Evaluation methods for physical activity-promoting mobile technologies: an interdisciplinary scoping review

Directory of Open Access Journals (Sweden)

Claire McCallum

2015-10-01

Full Text Available There are many thousands of mobile apps, wearables and other technologies available to support and promote physical activity. However, the rapidly evolving nature of these technologies means that the methodologies traditionally used to evaluate the effectiveness of behaviour change interventions (such as the randomised controlled trial may not be appropriate to evaluate their effectiveness. A scoping review was conducted to identify the methods currently being used to evaluate physical activity-promoting mobile technologies across health and computing science disciplines. In addition to the range of methods used, the review explored their strengths and weaknesses. The results improve understandings of when and why to use existing methods from health and computing science. Opportunities for combining and hybridising methods across the two disciplines are also identified. The review will be used to inform the development and piloting of novel, ‘fit-for-purpose’ research designs that will allow rigorous evaluation of the effectiveness of rapidly-evolving physical activity-promoting mobile technologies and their ‘active ingredients’ to build an evidence base of what works, why and for whom.

First principles calculation of point defects and mobility degradation in bulk AlSb for radiation detection application

International Nuclear Information System (INIS)

Lordi, V; Aberg, D; Erhart, P; Wu, K J

2007-01-01

The development of high resolution, room temperature semiconductor radiation detectors requires the introduction of materials with increased carrier mobility-lifetime (μτ) product, while having a band gap in the 1.4-2.2 eV range. AlSb is a promising material for this application. However, systematic improvements in the material quality are necessary to achieve an adequate μτ product. We are using a combination of simulation and experiment to develop a fundamental understanding of the factors which affect detector material quality. First principles calculations are used to study the microscopic mechanisms of mobility degradation from point defects and to calculate the intrinsic limit of mobility from phonon scattering. We use density functional theory (DFT) to calculate the formation energies of native and impurity point defects, to determine their equilibrium concentrations as a function of temperature and charge state. Perturbation theory via the Born approximation is coupled with Boltzmann transport theory to calculate the contribution toward mobility degradation of each type of point defect, using DFT-computed carrier scattering rates. A comparison is made to measured carrier concentrations and mobilities from AlSb crystals grown in our lab. We find our predictions in good quantitative agreement with experiment, allowing optimized annealing conditions to be deduced. A major result is the determination of oxygen impurity as a severe mobility killer, despite the ability of oxygen to compensation dope AlSb and reduce the net carrier concentration. In this case, increased resistivity is not a good indicator of improved material performance, due to the concomitant sharp reduction in μτ

Trace impurities analysis of aluminum nanopowder and its air combustion product

Science.gov (United States)

Kabanov, Denis V.; Merkulov, Viktor G.; Mostovshchikov, Andrey V.; Ilyin, Alexander P.

2018-03-01

Neutron activation analysis (NAA) allows estimating micro-concentrations of chemicals and analyzes tens of elements at one measurement. In this paper we have used NAA to examine metal impurities in the electroexplosive aluminum nanopowder (ANP) and its air-combustion products produced by burning in crucibles in an electric and magnetic field and without application of fields. It has been revealed that in the air-combustion products impurities content is reduced. The presence of impurities in the ANP is associated with electric explosion technology (erosion of electrode and chamber materials) and with the previous development of various nanopowders in the composition of this electric explosive device. NAA is characterized by a high sensitivity and reproducibility to elements content and low metering error. According to the obtained results it has been concluded that NAA metering error does not exceed 10% in the wide concentration range, from 0.01 to 2100 ppm, particularly. Besides, there is high reproducibility of the method that has been proved on macro-elements of Ca (>1000 ppm), Fe (>2000 ppm), and micro-elements as Sm, U, Ce, Sb, Th, etc. (<0.9 ppm). It is recommended to use an individual unit for the production of pure metal powders for electric explosion and production of nanopowders, which is possible with mass production of nanopowders.

Parametric dependences of impurity transport in the Tore Supra tokamak

International Nuclear Information System (INIS)

Parisot, Th.

2007-09-01

During this Ph.D. work, a full setup of tools for an experimental investigation of impurity transport has been developed on the Tore Supra tokamak. It includes a laser blow-off system for metallic impurity injections and developments for ITC (Impurity Transport Code), a transport code which allows the extraction of the experimental impurity transport coefficients (diffusion and convection velocity). This tool has been used to perform and analyse several experiments, to evidence parametric dependences of impurity transport. In a first experiment, a confinement time law for nickel in Tore Supra has been obtained as a function of collisionality ν * and normalized Larmor radius ρ * . Then the impurity charge Z role has been investigated in various conditions: ohmic regime with or without sawteeth, and sawtooth less L-mode with LH power. No Z effect is observed, consistently with theoretical predictions, whether neoclassical (NCLASS) or for turbulent transport with both non linear gyro-fluid (TRB) and quasilinear gyrokinetic (QuaLiKiz) simulations. An exception is found for LH heated plasmas where the confinement time seems to decrease for the heaviest impurities. This is not explained by any model available. The observed transport is close to neoclassical between sawtooth relaxations, in the centre (r q-1 ) of ohmic plasmas, turbulent outside. Without sawteeth, it is turbulent in the whole plasma, for ohmic or L mode discharges. The profile shape of the diffusion coefficient is here qualitatively different, with a stronger and deeper transition between the low diffusion central region and a more turbulent peripheral region for LH heated plasmas. (author)

Organic impurity profiling of 3,4-methylenedioxymethamphetamine (MDMA) synthesised from catechol.

Science.gov (United States)

Heather, Erin; Shimmon, Ronald; McDonagh, Andrew M

2015-03-01

This work examines the organic impurity profile of 3,4-methylenedioxymethamphetamine (MDMA) that has been synthesised from catechol (1,2-dihydroxybenzene), a common chemical reagent available in industrial quantities. The synthesis of MDMA from catechol proceeded via the common MDMA precursor safrole. Methylenation of catechol yielded 1,3-benzodioxole, which was brominated and then reacted with magnesium allyl bromide to form safrole. Eight organic impurities were identified in the synthetic safrole. Safrole was then converted to 3,4-methylenedioxyphenyl-2-propanone (MDP2P) using two synthetic methods: Wacker oxidation (Route 1) and an isomerisation/peracid oxidation/acid dehydration method (Route 2). MDMA was then synthesised by reductive amination of MDP2P. Thirteen organic impurities were identified in MDMA synthesised via Route 1 and eleven organic impurities were identified in MDMA synthesised via Route 2. Overall, organic impurities in MDMA prepared from catechol indicated that synthetic safrole was used in the synthesis. The impurities also indicated which of the two synthetic routes was utilised. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

A Survey of Online Activity Recognition Using Mobile Phones

NARCIS (Netherlands)

Shoaib, M.; Bosch, S.; Durmaz, O.; Scholten, Johan; Havinga, Paul J.M.

2015-01-01

Physical activity recognition using embedded sensors has enabled many context-aware applications in different areas, such as healthcare. Initially, one or more dedicated wearable sensors were used for such applications. However, recently, many researchers started using mobile phones for this

Spectroscopic impurity survey in Wendelstein 7-X

Energy Technology Data Exchange (ETDEWEB)

Buttenschoen, Birger; Burhenn, Rainer; Thomsen, Henning [Max-Planck-Institut fuer Plasmaphysik, Greifswald (Germany); Biel, Wolfgang; Assmann, Jochen; Hollfeld, Klaus-Peter [Forschungszentrum Juelich GmbH, Juelich (Germany); Collaboration: the Wendelstein 7-X Team

2016-07-01

The High Efficiency eXtreme ultraviolet Overview Spectrometer (HEXOS) has been developed specifically for impurity identification and survey purposes on the Wendelstein 7-X stellarator. This spectrometer system, consisting of four individual spectrometers, covers the wavelength range between λ=2.5 nm and λ=160 nm, observing the intense resonance lines of relevant Mg-, Na-, Be- and Li-like impurity ions as well as the high-Z W/Ta quasi-continua. During the first operation phase of W7-X, commissioning of HEXOS was finished by providing an in-situ wavelength calibration. The permanently acquired spectra are evaluated to monitor the overall impurity content in the plasma, and serve as an indicator for unintended plasma-wall contact possibly leading to machine damage. HEXOS results from the first operation phase of W7-X are presented and discussed with respect to future scientific exploitation of the available data.

Magnetic impurity coupled to interacting conduction electrons

International Nuclear Information System (INIS)

Schork, T.

1996-01-01

We consider a magnetic impurity which interacts by hybridization with a system of weakly correlated electrons and determine the energy of the ground state by means of a 1/N f expansion. The correlations among the conduction electrons are described by a Hubbard Hamiltonian and are treated to the lowest order in the interaction strength. We find that their effect on the Kondo temperature, T K , in the Kondo limit is twofold: first, the position of the impurity level is shifted due to the reduction of charge fluctuations, which reduces T K . Secondly, the bare Kondo exchange coupling is enhanced as spin fluctuations are enlarged. In total, T K increases. Both corrections require intermediate states beyond the standard Varma-Yafet ansatz. This shows that the Hubbard interaction does not just provide quasiparticles, which hybridize with the impurity, but also renormalizes the Kondo coupling. copyright 1996 The American Physical Society

Influence of impurities on the surface morphology of the TIBr crystal semiconductor

International Nuclear Information System (INIS)

Santos, Robinson A. dos; Silva, Julio B. Rodrigues da; Martins, Joao F.T.; Ferraz, Caue de M.; Costa, Fabio E. da; Mesquita, Carlos H. de; Hamada, Margarida M.; Gennari, Roseli F.

2013-01-01

The impurity effect in the surface morphology quality of TlBr crystals was evaluated, aiming a future application of these crystals as room temperature radiation semiconductor detectors. The crystals were purified and grown by the Repeated Bridgman technique. Systematic measurements were carried out for determining the stoichiometry, structure orientation, surface morphology and impurity of the crystal. A significant difference in the crystals impurity concentration was observed for almost all impurities, compared to those found in the raw material. The crystals wafer grown twice showed a surface roughness and grains which may be due to the presence of impurities on the surface, while those obtained with crystals grown three times presented a more uniform surface: even though, a smaller roughness was still observed. It was demonstrated that the impurities affect strongly the surface morphology quality of crystals. (author)

Stacking change in MoS2 bilayers induced by interstitial Mo impurities.

Science.gov (United States)

Cortés, Natalia; Rosales, Luis; Orellana, Pedro A; Ayuela, Andrés; González, Jhon W

2018-02-01

We use a theoretical approach to reveal the electronic and structural properties of molybdenum impurities between MoS 2 bilayers. We find that interstitial Mo impurities are able to reverse the well-known stability order of the pristine bilayer, because the most stable form of stacking changes from AA' (undoped) into AB' (doped). The occurrence of Mo impurities in different positions shows their split electronic levels in the energy gap, following octahedral and tetrahedral crystal fields. The energy stability is related to the accommodation of Mo impurities compacted in hollow sites between layers. Other less stable configurations for Mo dopants have larger interlayer distances and band gaps than those for the most stable stacking. Our findings suggest possible applications such as exciton trapping in layers around impurities, and the control of bilayer stacking by Mo impurities in the growth process.

Phase transition in one Josephson junction with a side-coupled magnetic impurity

Science.gov (United States)

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 impact of utilizing mobile phones to promote physical activity among post-secondary students: a scoping review.

Science.gov (United States)

Ly, Hieu

2016-01-01

A commitment to regular physical activity may reduce the risks of chronic diseases for young adults. Internationally, the majority of post-secondary students are insufficiently active for health benefits. Novel health strategies and interventions utilizing mobiles phones could increase post-secondary students' physical activity levels. However, there is contradictory evidence to support the use of mobile phones to promote physical activity, and a scoping review could provide further insights into this topic. The purpose of this study was to conduct a scoping review to explore the existing literature and investigate what is currently known about the use of mobile phones to enhance physical activity levels among post-secondary students. A total of 84 articles were identified from the literature search, and six studies were selected for data analysis. Two major themes were supported by the evidence, which included: (I) the relationship between mobile phones and physical activity levels; and (II) students' perceptions of mobile phones. Goal setting principles combined with text message interventions were reported to have significant influences on students' physical activity levels. Students expressed mixed feelings about coaching elements of apps and posting personal results on social networking websites. No studies reported the use of objective physical activity measurements. In conclusion, mobile phone technologies such as text message reminders could be included in health interventions to enhance post-secondary students' physical activity levels. There is limited evidence available on this topic and additional research is warranted to establish a clearer understanding of the relationship between mobile phones and post-secondary students' physical activity.

Application of the remote microphone method to active noise control in a mobile phone.

Science.gov (United States)

Cheer, Jordan; Elliott, Stephen J; Oh, Eunmi; Jeong, Jonghoon

2018-04-01

Mobile phones are used in a variety of situations where environmental noise may interfere with the ability of the near-end user to communicate with the far-end user. To overcome this problem, it might be possible to use active noise control technology to reduce the noise experienced by the near-end user. This paper initially demonstrates that when an active noise control system is used in a practical mobile phone configuration to minimise the noise measured by an error microphone mounted on the mobile phone, the attenuation achieved at the user's ear depends strongly on the position of the source generating the acoustic interference. To help overcome this problem, a remote microphone processing strategy is investigated that estimates the pressure at the user's ear from the pressure measured by the microphone on the mobile phone. Through an experimental implementation, it is demonstrated that this arrangement achieves a significant improvement in the attenuation measured at the ear of the user, compared to the standard active control strategy. The robustness of the active control system to changes in both the interfering sound field and the position of the mobile device relative to the ear of the user is also investigated experimentally.

Gate-modulated conductance of few-layer WSe{sub 2} field-effect transistors in the subgap regime: Schottky barrier transistor and subgap impurity states

Energy Technology Data Exchange (ETDEWEB)

Wang, Junjie; Feng, Simin [Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Rhodes, Daniel; Balicas, Luis [National High Magnetic Field Lab, Florida State University, Tallahassee, Florida 32310 (United States); Nguyen, Minh An T. [Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Watanabe, K.; Taniguchi, T. [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan); Mallouk, Thomas E. [Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Terrones, Mauricio [Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Zhu, J., E-mail: jzhu@phys.psu.edu [Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

2015-04-13

Two key subjects stand out in the pursuit of semiconductor research: material quality and contact technology. The fledging field of atomically thin transition metal dichalcogenides (TMDCs) faces a number of challenges in both efforts. This work attempts to establish a connection between the two by examining the gate-dependent conductance of few-layer (1-5L) WSe{sub 2} field effect devices. Measurements and modeling of the subgap regime reveal Schottky barrier transistor behavior. We show that transmission through the contact barrier is dominated by thermionic field emission (TFE) at room temperature, despite the lack of intentional doping. The TFE process arises due to a large number of subgap impurity states, the presence of which also leads to high mobility edge carrier densities. The density of states of such impurity states is self-consistently determined to be approximately 1–2 × 10{sup 13}/cm{sup 2}/eV in our devices. We demonstrate that substrate is unlikely to be a major source of the impurity states and suspect that lattice defects within the material itself are primarily responsible. Our experiments provide key information to advance the quality and understanding of TMDC materials and electrical devices.

The influence of optical parameters on impurity determinations by IR spectroscopy

International Nuclear Information System (INIS)

Lombard, O.J.

1985-01-01

The important role of impurities in semiconductor materials is the subject of continuous research. The concentration of interstitial oxygen impurities in silicon are determined with the aid of infrared spectroscopy. The maximum absorption coefficient of the oxygen absorption peak, centered at 9,06 μm, is determined and the impurity concentration is then calculated using a calibration factor. This procedure was evaluated, paying particular attention to those optical parameters which may influence these impurity determinations. A thorough discussion of the theoretical and experimental aspects of infrared spectroscopy in general is followed by an overview of previous experimental work. This lead to some theoretical analysis regarding the influence of the index of refraction, the index of absorption and multiple reflections in the silicon wafer on impurity determinations. This lead to specific experimental investigations. The influence of the surface morphology of samples on impurity determinations was studied by determining the reflectance of silicon surfaces. It was established that the surface reflectance plays a role and that it must be taken into consideration for accurate impurity concentration determinations. The most accurate values for the absorption coefficient due to oxygen in silicon are calculated. This requires that the surface of the silicon wafers must be highly polished for the formula to be valid. Acceptable values for the absorption coefficient of damaged surfaces are obtained if the uncorrected formula is used. Experimental results may deviate as much as 32% from the real impurity concentration if the wrong formula is used to calculate the absorption coefficient of oxygen in silicon at 9,06 μm

On the radiative effects of light-absorbing impurities on snowpack evolution

Science.gov (United States)

Dumont, M.; Tuzet, F.; Lafaysse, M.; Arnaud, L.; Picard, G.; Lejeune, Y.; Lamare, M.; Morin, S.; Voisin, D.; Di Mauro, B.

2017-12-01

The presence of light absorbing impurities in snow strongly decreases snow reflectance leading to an increase in the amount of solar energy absorbed by the snowpack. This effect is also known as impurities direct radiative effect. The change in the amount of energy absorbed by the snowpack modifies the temperature profile inside the snowpack and in turn snow metamorphism (impurities indirect radiative effects). In this work, we used the detailed snowpack model SURFEX/ISBA-Crocus with an explicit representation of snow light-absorbing impurities content (Tuzet et al., 2017) fed by medium-resolution ALADIN-Climate atmospheric model to represent dust and black carbon atmospheric deposition fluxes. The model is used at two sites: Col de Porte (medium elevation site in the French Alps) and Torgnon (high elevation site in the Italian Alps). The simulations are compared to in-situ observations and used to quantify the effects of light-absorbing impurities on snow melt rate and timing. The respective parts of the direct and indirect radiative effects of light-absorbing impurities in snow are also computed for the two sites, emphasizing the need to account for the interactions between snow metamorphism and LAI radiative properties, to accurately predict the effects of light-absorbing impurities in snow. Moreover, we describe how automated hyperspectral reflectance can be used to estimate effective impurities surface content in snow. Finally we demonstrate how these reflectances measurements either from in situ or satellite data can be used via an assimilation scheme to constrain snowpack ensemble simulations and better predict the snowpack state and evolution.

Identification of impurities in sodium and its purification

International Nuclear Information System (INIS)

Subbotin, B.I.; Voltchkov, L.G.; Kozlov, F.A.; Zagorulko, Yu.I.; Kuznetsov, E.K.

1976-01-01

The paper presents some investigation results on sodium technology. In particular, a description is given of a calculation method for evaluation of sodium-cover gas-impurities equilibrium compositions as well as experimental results on development of methods for sodium sampling, equipment for non-metallic impurities (oxygen, hydrogen, carbon) constant control in sodium. The investigation results on sodium purification with cold traps are presented

Spectroscopical studies of impurities in the belt pinch HECTOR

International Nuclear Information System (INIS)

Singethan, J.

1981-04-01

In this paper UV-line-intensity measurements of impurities are presented, which have been performed in the belt-pinch HECTOR. From the line-intensities impurity concentrations and information on the radiation losses is be obtained. At temperatures below 100 eV, the energy loss due to line emission of oxygen and carbon impurities is one of the most important electron energy loss mechanisms. Thus the measurement and calculation of the radiation losses is of particular relevance. Furthermore the electron temperature time dependence can be obtained by comparing the line intensity time dependence with the solution of the respective rate equations. (orig./HT) [de

Prevention of serious impurity penetration into water-steam circuits

International Nuclear Information System (INIS)

Burgmann, F.; Bursik, A.; Flunkert, F.; Nieder, R.

1977-01-01

In consequence of reports from several power Plants concerning heavy damages due to penetrations of impurities into the water-steam circuit, the VGB Sub-Committee 'Water Chemistry in Thermal Power Plants' has established a working group to check-up how serious impurity penetration can be avoided. The lecture describes possible danger points. Suitable technical arrangements for the avoidance of penetrations, and possibilities for monitoring will be discussed. Penetration of impurities cannot be avoided with absolute reliability, even when the recommended arrangements and usual monitoring are realized. Additional measures for the protection of water steam circuits will be suggested. (orig.) [de

Impurity effects on the magnetic ordering in chromium

International Nuclear Information System (INIS)

Fishman, R.S.

1992-05-01

It is well-known that impurities profoundly alter the magnetic properties of chromium. While vanadium impurities suppress the Neel temperature T N , manganese impurities enhanced T N substantially. As evidenced by neutron scattering experiments, doping with as little as 0.2% vanadium changes the transition from weakly first order to second order. Young and Sokoloff explained that the first-order transition in pure chromium is caused by a charge-density wave which is the second harmonic of the spin-density wave. By examining the subtle balance between the spin-density and charge- density wave terms in the mean-field free energy, we find that the first-order transition is destroyed when the vanadium concentration exceeds about 0.15%, in agreement with experiments

Impurity Effects in Electroplated-Copper Solder Joints

Directory of Open Access Journals (Sweden)

Hsuan Lee

2018-05-01

Full Text Available Copper (Cu electroplating is a mature technology, and has been extensively applied in microelectronic industry. With the development of advanced microelectronic packaging, Cu electroplating encounters new challenges for atomic deposition on a non-planar substrate and to deliver good throwing power and uniform deposit properties in a high-aspect-ratio trench. The use of organic additives plays an important role in modulating the atomic deposition to achieve successful metallic coverage and filling, which strongly relies on the adsorptive and chemical interactions among additives on the surface of growing film. However, the adsorptive characteristic of organic additives inevitably results in an incorporation of additive-derived impurities in the electroplated Cu film. The incorporation of high-level impurities originating from the use of polyethylene glycol (PEG and chlorine ions significantly affects the microstructural evolution of the electroplated Cu film, and the electroplated-Cu solder joints, leading to the formation of undesired voids at the joint interface. However, the addition of bis(3-sulfopropyl disulfide (SPS with a critical concentration suppresses the impurity incorporation and the void formation. In this article, relevant studies were reviewed, and the focus was placed on the effects of additive formula and plating parameters on the impurity incorporation in the electroplated Cu film, and the void formation in the solder joints.

Two-dimensional impurity transport calculations for a high recycling divertor

International Nuclear Information System (INIS)

Brooks, J.N.

1986-04-01

Two dimensional analysis of impurity transport in a high recycling divertor shows asymmetric particle fluxes to the divertor plate, low helium pumping efficiency, and high scrapeoff zone shielding for sputtered impurities

Usability of Mobile Phones in Physical Activity-Rrelated Research: A Systematic Review

Science.gov (United States)

Monroe, Courtney M.; Thompson, Dixie L.; Bassett, David R., Jr.; Fitzhugh, Eugene C.; Raynor, Hollie A.

2015-01-01

Background: The use of mobile phones for physical activity (PA) promotion and assessment represents an attractive research area because this technology is characterized by a widespread reach and dynamic features. Purpose: The purpose of this study was to conduct a systematic review of mobile phone-based approaches for encouraging and assessing PA.…

Mobility disability and the pattern of accelerometer-derived sedentary and physical activity behaviors in people with multiple sclerosis

Science.gov (United States)

Ezeugwu, Victor; Klaren, Rachel E.; A. Hubbard, Elizabeth; Manns, Patricia (Trish); Motl, Robert W.

2015-01-01

Objective Low physical activity and high sedentary behavior levels are major concerns in persons with multiple sclerosis (MS) and these differ depending on the level of mobility disability. However, the manner in which daily activity is accumulated is currently unknown in this population. Methods A secondary analysis was performed on a combined data set of persons with MS from two previous investigations of physical activity and symptomatic or quality of life outcomes in the United States over a two year period (2007–2009). Mobility disability status was determined using the Patient Determined Disease Steps (PDDS) while activity behavior was objectively monitored using an ActiGraph accelerometer for 7 days. Results Persons with MS who have mobility disability were involved in sedentary behavior, light and moderate intensity activity for 65%, 34% and 1% of the day, respectively compared to 60%, 37%, and 3%, respectively in those without mobility disability (p mobility disability status. Compared to those without mobility disability, the average number of sedentary bouts longer than 30 min was greater in those with mobility disability (p = 0.016). Conclusion Persons with MS with mobility disability are less active, engage in more sedentary behavior and accumulate prolonged sedentary bouts. PMID:26844077

The electronic structure of impurities in semiconductors

CERN Multimedia

Nylandsted larsen, A; Svane, A

2002-01-01

The electronic structure of isolated substitutional or interstitial impurities in group IV, IV-IV, and III-V compound semiconductors will be studied. Mössbauer spectroscopy will be used to investigate the incorporation of the implanted isotopes on the proper lattice sites. The data can be directly compared to theoretical calculations using the LMTO scheme. Deep level transient spectroscopy will be used to identify the band gap levels introduced by metallic impurities, mainly in Si~and~Si$ _{x}$Ge$_{1-x}$. \\\\ \\\\

40 CFR 159.179 - Metabolites, degradates, contaminants, and impurities.

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Metabolites, degradates, contaminants.../Benefit Information § 159.179 Metabolites, degradates, contaminants, and impurities. (a) Metabolites and... degradation of less than 10 percent in a 30-day period. (b) Contaminants and impurities. The presence in any...

Effects of electronically neutral impurities on muonium in germanium

International Nuclear Information System (INIS)

Clawson, C.W.; Crowe, K.M.; Haller, E.E.; Rosenblum, S.S.; Brewer, J.H.

1983-04-01

Low-temperature measurements of muonium parameters in various germanium crystals have been performed. We have measured crystals with different levels of neutral impurities, with and without dislocations, and with different annealing histories. The most striking result is the apparent trapping of Mu by silicon impurities in germanium

Study of radioactive impurities in neutron transmutation doped germanium

Energy Technology Data Exchange (ETDEWEB)

Mathimalar, S.; Dokania, N.; Singh, V. [India-based Neutrino Observatory, Tata Institute of Fundamental Research, Mumbai 400 005 (India); Homi Bhabha National Institute, Anushaktinagar, Mumbai 400 094 (India); Nanal, V., E-mail: nanal@tifr.res.in [Department of Nuclear and Atomic Physics, Tata Institute of Fundamental Research, Mumbai 400 005 (India); Pillay, R.G. [Department of Nuclear and Atomic Physics, Tata Institute of Fundamental Research, Mumbai 400 005 (India); Shrivastava, A. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Jagadeesan, K.C.; Thakare, S.V. [Isotope Production and Applications Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

2015-02-21

A program to develop low temperature (mK) sensors with neutron transmutation doped Ge for rare event studies with a cryogenic bolometer has been initiated. For this purpose, semiconductor grade Ge wafers are irradiated with thermal neutron flux from Dhruva reactor at Bhabha Atomic Research Centre (BARC), Mumbai. Spectroscopic studies of irradiated samples have revealed that the environment of the capsule used for irradiating the sample leads to significant levels of {sup 65}Zn, {sup 110m}Ag and {sup 182}Ta impurities, which can be reduced by chemical etching of approximately ∼50μm thick surface layer. From measurements of the etched samples in the low background counting setup, activity due to trace impurities of {sup 123}Sb in bulk Ge is estimated to be ∼1Bq/g after irradiation. These estimates indicate that in order to use the NTD Ge sensors for rare event studies, a cooldown period of ∼2 years would be necessary to reduce the radioactive background to ≤1mBq/g.

Can impurities from soil-contaminated coffees reach the cup?

International Nuclear Information System (INIS)

Tagliaferro, F.S.; De Nadai Fernandes, E.A.; Bacchi, M.A.; Joacir De Franca, E.; Bode, P.

2007-01-01

Depending on the harvest conditions, coffee beans can be contaminated by soil when dropped to the ground. It is well known that agricultural soils act as sinks for agrochemicals applied to the crops. While coffee is brewed, substances present in the roasted and ground coffee beans are extracted by hot water, emphasizing the need to assess the possible transfer of impurities from the soil to the beverage. Soil-contaminated samples of roasted coffee beans were split into 2 groups according to the treatments: (a) washed and ground and (b) only ground. Brewing was performed in a household espresso machine for both coffees. The resulting beverage was freeze-dried and the elemental composition determined by instrumental neutron activation analysis (INAA). The mass fractions of the terrigenous elements Fe, La, Sc, Sm and Th in the freeze-dried non-washed coffee beverages were, at least, 2 times higher than in the washed samples. These elements are tracers of the soil, indicating that the impurities from the soil reached the beverage. (author)

Report on intercomparison exercise SR-54. Determination of impurities in U3O8

International Nuclear Information System (INIS)

Doubek, N.; Bagliano, G.; Deron, S.

1984-04-01

The report presents results of a laboratory intercomparison of impurities in U 3 O 8 sample organized by the IAEA's Analytical Quality Control Service. Twelve laboratories in 11 countries sent their results. The framework of the intercomparison was therefore conceived mainly as a ''mean'' to laboratories dealing with analysis of impurities in uranium samples to check the reliability of their results. The evaluation was based on 97 laboratory means obtained with emission spectroscopy, atomic absorption techniques and neutron activation analysis. The concentration of three elements could be certified as a result of this intercomparison; informational values could be established for an additional six elements

High-frequency EPR of surface impurities on nanodiamond

Science.gov (United States)

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).

Self-consistent gyrokinetic modeling of neoclassical and turbulent impurity transport

Science.gov (United States)

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.

Impurities block the alpha to omega martensitic transformation in titanium.

Science.gov (United States)

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.

The mPED randomized controlled clinical trial: applying mobile persuasive technologies to increase physical activity in sedentary women protocol

Directory of Open Access Journals (Sweden)

Fukuoka Yoshimi

2011-12-01

Full Text Available Abstract Background Despite the significant health benefits of regular physical activity, approximately half of American adults, particularly women and minorities, do not meet the current physical activity recommendations. Mobile phone technologies are readily available, easily accessible and may provide a potentially powerful tool for delivering physical activity interventions. However, we need to understand how to effectively apply these mobile technologies to increase and maintain physical activity in physically inactive women. The purpose of this paper is to describe the study design and protocol of the mPED (mobile phone based physical activity education randomized controlled clinical trial that examines the efficacy of a 3-month mobile phone and pedometer based physical activity intervention and compares two different 6-month maintenance interventions. Methods A randomized controlled trial (RCT with three arms; 1 PLUS (3-month mobile phone and pedometer based physical activity intervention and 6-month mobile phone diary maintenance intervention, 2 REGULAR (3-month mobile phone and pedometer based physical activity intervention and 6-month pedometer maintenance intervention, and 3 CONTROL (pedometer only, but no intervention will be conducted. A total of 192 physically inactive women who meet all inclusion criteria and successfully complete a 3-week run-in will be randomized into one of the three groups. The mobile phone serves as a means of delivering the physical activity intervention, setting individualized weekly physical activity goals, and providing self-monitoring (activity diary, immediate feedback and social support. The mobile phone also functions as a tool for communication and real-time data capture. The primary outcome is objectively measured physical activity. Discussion If efficacy of the intervention with a mobile phone is demonstrated, the results of this RCT will be able to provide new insights for current behavioral

The mPED randomized controlled clinical trial: applying mobile persuasive technologies to increase physical activity in sedentary women protocol.

Science.gov (United States)

Fukuoka, Yoshimi; Komatsu, Judith; Suarez, Larry; Vittinghoff, Eric; Haskell, William; Noorishad, Tina; Pham, Kristin

2011-12-14

Despite the significant health benefits of regular physical activity, approximately half of American adults, particularly women and minorities, do not meet the current physical activity recommendations. Mobile phone technologies are readily available, easily accessible and may provide a potentially powerful tool for delivering physical activity interventions. However, we need to understand how to effectively apply these mobile technologies to increase and maintain physical activity in physically inactive women. The purpose of this paper is to describe the study design and protocol of the mPED (mobile phone based physical activity education) randomized controlled clinical trial that examines the efficacy of a 3-month mobile phone and pedometer based physical activity intervention and compares two different 6-month maintenance interventions. A randomized controlled trial (RCT) with three arms; 1) PLUS (3-month mobile phone and pedometer based physical activity intervention and 6-month mobile phone diary maintenance intervention), 2) REGULAR (3-month mobile phone and pedometer based physical activity intervention and 6-month pedometer maintenance intervention), and 3) CONTROL (pedometer only, but no intervention will be conducted). A total of 192 physically inactive women who meet all inclusion criteria and successfully complete a 3-week run-in will be randomized into one of the three groups. The mobile phone serves as a means of delivering the physical activity intervention, setting individualized weekly physical activity goals, and providing self-monitoring (activity diary), immediate feedback and social support. The mobile phone also functions as a tool for communication and real-time data capture. The primary outcome is objectively measured physical activity. If efficacy of the intervention with a mobile phone is demonstrated, the results of this RCT will be able to provide new insights for current behavioral sciences and mHealth. ClinicalTrials.gov#:NCTO1280812.

Determination of sulphur-35 impurity in solutions of phosphorus-32

International Nuclear Information System (INIS)

Rodriguez Pasques, R.H.; Iglicki, F.A; Cittadini, P.E.

1982-01-01

A method has been developed in order to evaluate the activity of sulphur-35 impurity in solutions of phosphorus-32. The procedure is based on the precipitation on benzidine sulphate in acid solution and further purification by dissolving and reprecipitating under appropriate conditions. 35 S beta radiation is measured with and end-window gas counter. A correction for any remaining 32 P is determined by differential absorption through aluminum. (author) [es

Influence of impurities on silicide contact formation

International Nuclear Information System (INIS)

Kazdaev, Kh.R.; Meermanov, G.B.; Kazdaev, R.Kh.

2002-01-01

Research objectives of this work are to investigate the influence of light impurities implantation on peculiarities of the silicides formation in molybdenum monocrystal implanted by silicon, and in molybdenum films sputtered on silicon substrate at subsequent annealing. Implantation of the molybdenum samples was performed with silicon ions (90 keV, 5x10 17 cm -2 ). Phase identification was performed by X ray analysis with photographic method of registration. Analysis of the results has shown the formation of the molybdenum silicide Mo 3 Si at 900 deg. C. To find out the influence of impurities present in the atmosphere (C,N,O) on investigated processes we have applied combined implantation. At first, molybdenum was implanted with ions of the basic component (silicon) and then -- with impurities ions. Acceleration energies (40keV for C, 45 keV for N and 50 keV for O) were chosen to obtain the same distribution profiles for basic and impurities ions. Ion doses were 5x10 17 cm -2 for Si-ions and 5x10 16 cm -2 - for impurities. The most important results are reported here. The first, for all three kinds of impurities the decreased formation temperatures of the phase Mo 3 Si were observed; in the case of C and N it was ∼100 deg. and in the case of nitrogen - ∼200 deg. Further, simultaneously with the Mo 3 Si phase, the appearance of the rich-metal phase Mo 5 Si 3 was registered (not observed in the samples without additional implantation). In case of Mo/Si-structure, the implantation of the impurities (N,O) was performed to create the peak concentration (∼4at/%) located in the middle of the molybdenum film (∼ 150nm) deposited on silicon substrate. Investigation carried out on unimplanted samples showed the formation of the silicide molybdenum MoSi 2 , observed after annealing at temperatures 900/1000 deg. C, higher than values 500-600 deg. C reported in other works. It is discovered that electrical conductivity of Mo 5 Si 3 -films synthesized after impurities

Defect-impurity interactions in irradiated germanium

International Nuclear Information System (INIS)

Cleland, J.W.; James, F.J.; Westbrook, R.D.

1975-07-01

Results of experiments are used to formulate a better model for the structures of lattice defects and defect-impurity complexes in irradiated n-type Ge. Single crystals were grown by the Czochralski process from P, As, or Sb-doped melts, and less than or equal to 10 15 to greater than or equal to 10 17 oxygen cm -3 was added to the furnace chamber after approximately 1 / 3 of the crystal had been solidified. Hall coefficient and resistivity measurements (at 77 0 K) were used to determine the initial donor concentration due to the dopant and clustered oxygen, and infrared absorption measurements (at 11.7 μ) were used to determine the dissociated oxygen concentration. Certain impurity and defect-impurity interactions were then investigated that occurred as a consequence of selected annealing, quenching, Li diffusion, and irradiation experiments at approximately 300 0 K with 60 Co photons, 1.5 to 2.0 MeV electrons, or thermal energy neutrons. Particular attention was given to determining the electrical role of the irradiation produced interstitial and vacancy, and to look for any evidence from electrical and optical measurements of vacancy--oxygen, lithium--oxygen, and lithium--vacancy interactions. (U.S.)

Surface Characterization of Impurities in Superconducting Niobium for Radio Frequency (RF) Cavities used in Particle Accelerators

Science.gov (United States)

Maheshwari, Prateek

Niobium (Nb) is the material of choice for Superconducting Radio Frequency (SRF) Cavities used in particle accelerators owing to its high critical temperature (Tc = 9.2 K) and critical magnetic field (≈ 200mT). However, niobium tends to harbor interstitial impurities such as H, C, O and N, which are detrimental to cavity performance. Since the magnetic field penetration depth (lambda) of niobium is 40nm, it is important to characterize these impurities using surface characterization techniques. Also, it is known that certain heat treatments improve cavity efficiency via interstitial impurity removal from the surface of niobium. Thus, a systematic study on the effect of these heat treatments on the surface impurity levels is needed. In this work, surface analysis of both heat treated and non heat treated (120°C-1400°C) large grain (single crystal) bulk niobium samples was performed using secondary ion mass spectrometry (SIMS) and Transmission Electron Microscopy (TEM). Impurity levels were compared on the surface using SIMS after various types of heat treatments expected to improve cavity performance, and the effect of these heat treatments on the surface impurities were examined. SIMS characterization of ion implanted standards of C, N, O, D showed that quantification of C, N and O impurities in Nb is achievable and indicated that H is very mobile in Nb. It was hence determined that quantification of H in Nb is not possible using SIMS due to its high diffusivity in Nb. However, a comparative study of the high temperature heat treated (600°C-1400°C) and non heat treated (control) samples revealed that hydrogen levels decreased by upto a factor of 100. This is attributed to the dissociation of the niobium surface oxide layer, which acts as a passivating film on the surface, and subsequent desorption of hydrogen. Reformation of this oxide layer on cool down disallows any re-absorption of hydrogen, indicating that the oxide acts as a surface barrier for

Significance of impurities in the safety evaluation of crop protection products - (IUPAC technical report)

NARCIS (Netherlands)

Ambrus, A.; Hamilton, D.J.; Kuiper, H.A.; Racke, K.D.

2003-01-01

There may be substantial differences in the chemical composition of technical-grade products of the same active ingredient manufactured under different conditions, from different raw materials, or by different routes of synthesis. Resulting differences in impurity content may significantly affect

Spectroscopic and electron-ion collision data for plasma impurities

International Nuclear Information System (INIS)

Faenov, A.; Marchand, R.; Tawara, H.; Vainshtein, L.; Wiese, W.

1992-01-01

This Working Group Report briefly reviews and summarizes the available spectroscopic and electron-ion collision data for plasma impurities. Included are lithium, neon, and argon, which, although they are not plasma impurities per se, are introduced into the plasma through the application of diagnostic techniques. 32 refs, 2 tabs

Plasma impurity-control studies in CTX

International Nuclear Information System (INIS)

Barnes, C.W.; Henins, I.; Hoida, H.W.; Jarboe, T.R.; Linford, R.K.; Marshall, J.; Sherwood, A.R.; Tuszewski, M.

1981-01-01

In the past, magnetized coaxial gun generated Compact Toroids (CTs) have exhibited magnetic field and density lifetimes of about 250 to 350 μs and electron temperatures of about 10 eV. In recent experiments, after hydrogen discharge cleaning the gun and flux conserver surfaces, the lifetimes have been extended to 550 μs. This improvement in lifetime, together with spectroscopic and bolometric measurements, are consistent with the interpretation that the CT plasma losses are impurity dominated and that discharge cleaning is reducing the impurities. Details of these measurements are described as well as successful experiments which led to a more open flux conserver

Plasma impurity-control studies in CTX

Energy Technology Data Exchange (ETDEWEB)

Barnes, C.W.; Henins, I.; Hoida, H.W.; Jarboe, T.R.; Linford, R.K.; Marshall, J.; Sherwood, A.R.; Tuszewski, M.

1981-01-01

In the past, magnetized coaxial gun generated Compact Toroids (CTs) have exhibited magnetic field and density lifetimes of about 250 to 350 ..mu..s and electron temperatures of about 10 eV. In recent experiments, after hydrogen discharge cleaning the gun and flux conserver surfaces, the lifetimes have been extended to 550 ..mu..s. This improvement in lifetime, together with spectroscopic and bolometric measurements, are consistent with the interpretation that the CT plasma losses are impurity dominated and that discharge cleaning is reducing the impurities. Details of these measurements are described as well as successful experiments which led to a more open flux conserver.

Room-temperature mobility above 2200 cm{sup 2}/V·s of two-dimensional electron gas in a sharp-interface AlGaN/GaN heterostructure

Energy Technology Data Exchange (ETDEWEB)

Chen, Jr-Tai, E-mail: jrche@ifm.liu.se; Persson, Ingemar; Nilsson, Daniel; Hsu, Chih-Wei; Palisaitis, Justinas; Forsberg, Urban; Persson, Per O. Å.; Janzén, Erik [Department of Physics, Chemistry, and Biology, Linköping University, SE 581 83 Linköping (Sweden)

2015-06-22

A high mobility of 2250 cm{sup 2}/V·s of a two-dimensional electron gas (2DEG) in a metalorganic chemical vapor deposition-grown AlGaN/GaN heterostructure was demonstrated. The mobility enhancement was a result of better electron confinement due to a sharp AlGaN/GaN interface, as confirmed by scanning transmission electron microscopy analysis, not owing to the formation of a traditional thin AlN exclusion layer. Moreover, we found that the electron mobility in the sharp-interface heterostructures can sustain above 2000 cm{sup 2}/V·s for a wide range of 2DEG densities. Finally, it is promising that the sharp-interface AlGaN/GaN heterostructure would enable low contact resistance fabrication, less impurity-related scattering, and trapping than the AlGaN/AlN/GaN heterostructure, as the high-impurity-contained AlN is removed.

Impurity penetration and transport during VH-mode on DIII-D

International Nuclear Information System (INIS)

Lippmann, S.I.; Evans, T.E.; Jackson, G.L.; West, W.P.

1992-05-01

A new modeling effort is made in order to understand the observed relatively low levels of impurity contamination during the VH-mode phase on DIII-D, as compared to those observed during the H-mode phase of selected discharges. The key element is the inclusion of the real 2-D flux surface geometry in the prediction of impurity penetration of sputtered atoms through the scrape-off layer into the core plasma. Of the elements which determine the impurity content in the plasma: sputtering yield, penetration, and core transport, the penetration through the scrape-off layer is found to be the most determinative factor. The low impurity content in VH-mode is attributed to the development of a scrape-off layer with higher density and temperature properties than those normally obtained in H-mode

Human movement activity classification approaches that use wearable sensors and mobile devices

Science.gov (United States)

Kaghyan, Sahak; Sarukhanyan, Hakob; Akopian, David

2013-03-01

Cell phones and other mobile devices become part of human culture and change activity and lifestyle patterns. Mobile phone technology continuously evolves and incorporates more and more sensors for enabling advanced applications. Latest generations of smart phones incorporate GPS and WLAN location finding modules, vision cameras, microphones, accelerometers, temperature sensors etc. The availability of these sensors in mass-market communication devices creates exciting new opportunities for data mining applications. Particularly healthcare applications exploiting build-in sensors are very promising. This paper reviews different approaches of human activity recognition.

Studies of impurity recycling by the collector probe technique

International Nuclear Information System (INIS)

Hildebrandt, D.; Grote, H.; Herrmann, A.; Laux, M.; Pech, P.; Reiner, H.D.; Wolff, H.

1987-01-01

In order to study recycling effects of the nonintrinsic impurity Li discharges with and without LiD-pellet injection were investigated. The observed maximum impurity level of Li in the SOL plasma of discharges without injection reaches less than 10% of that observed in discharges with injection. The measurements offer the possibility to distinguish between influxes from the wall and those which reach the collector probe via the core plasma. The time evolution, orientation and radial dependence of the impurity fluxes are characteristic features of their origin. The consideration of all these features facilitates a better understanding of collector probe measurements in the SOL-plasma. (orig.)

Patterns induced by magnetic impurities in d-wave superconductors

International Nuclear Information System (INIS)

Zuo Xianjun; Gong Changde; Zhou Yuan

2010-01-01

We investigate the modulated patterns induced by magnetic impurities in d-wave superconductors (DSCs) near optimal doping based on the t-t ' -U-V model. Modulated checkerboard patterns with periodicity of eight or four lattice constants (8a or 4a) in the spin-, charge- and DSC orders are observed. Moreover, the checkerboard modulation in the spin order appear to be robust against parameter changes, which is consistent with neutron-scattering experiments. For the two-impurity case, a modulated stripe-like spin order with periodicity 8a is induced, which coexists with the DSC order. Further experiments of magnetic impurity substitution in DSCs are expected to check these results.

Patterns induced by magnetic impurities in d-wave superconductors

Science.gov (United States)

Zuo, Xian-Jun; Gong, Chang-De; Zhou, Yuan

2010-07-01

We investigate the modulated patterns induced by magnetic impurities in d-wave superconductors (DSCs) near optimal doping based on the t-t-U-V model. Modulated checkerboard patterns with periodicity of eight or four lattice constants (8 a or 4 a) in the spin-, charge- and DSC orders are observed. Moreover, the checkerboard modulation in the spin order appear to be robust against parameter changes, which is consistent with neutron-scattering experiments. For the two-impurity case, a modulated stripe-like spin order with periodicity 8 a is induced, which coexists with the DSC order. Further experiments of magnetic impurity substitution in DSCs are expected to check these results.

Nonlinear excitations in two-dimensional molecular structures with impurities

DEFF Research Database (Denmark)

Gaididei, Yuri Borisovich; Rasmussen, Kim; Christiansen, Peter Leth

1995-01-01

We study the nonlinear dynamics of electronic excitations interacting with acoustic phonons in two-dimensional molecular structures with impurities. We show that the problem is reduced to the nonlinear Schrodinger equation with a varying coefficient. The latter represents the influence...... of the impurity. Transforming the equation to the noninertial frame of reference coupled with the center of mass we investigate the soliton behavior in the close vicinity of the impurity. With the help of the lens transformation we show that the soliton width is governed by an Ermakov-Pinney equation. We also...... excitations. Analytical results are in good agreement with numerical simulations of the nonlinear Schrodinger equation....

Finite-temperature behavior of an impurity in the spin-1/2 XXZ chain

International Nuclear Information System (INIS)

Yahagi, Ryoko; Deguchi, Tetsuo; Sato, Jun

2014-01-01

We study the zero- and the finite-temperature behavior of the integrable spin-1/2 XXZ periodic chain with an impurity by the algebraic and thermal Bethe ansatz methods. We evaluate the local magnetization on the impurity site at zero temperature analytically and derive the impurity susceptibility exactly from it. In the graphs of the impurity specific heat versus temperature, we show how the impurity spin becomes more liberated from the bulk many-body effect as the exchange coupling between the impurity spin and other spins decreases and that at low temperature it couples strongly to them such as in the Kondo effect. Thus, we observe not only the crossover behavior from the high- to the low-temperature regime, but another from the N-site chain to the (N − 1)-site chain with a free impurity spin. We also show that the estimate of the Wilson ratio at a given low temperature is independent of the impurity parameter if its absolute value is small enough with respect to the temperature and the universality class is described by the XXZ anisotropy in terms of the dressed charge. (paper)

Analysis of two commercially available bortezomib products: differences in assay of active agent and impurity profile.

Science.gov (United States)

Byrn, Stephen R; Tishmack, Patrick A; Milton, Mark J; van de Velde, Helgi

2011-06-01

The analytical properties of two commercially available bortezomib products (VELCADE(®) and Bortenat) were compared using nuclear magnetic resonance, mass spectrometry, high-performance liquid chromatography, and gas chromatography. The data showed differences between the two products. Based on these data, Bortenat samples contained more active ingredients than indicated by the label (mean, 116.5% and 117.9% of label, in 2-mg and 3.5-mg vials, respectively). In comparison, VELCADE samples contained a mean of 99.3% of active ingredient, which was consistent with the approved specification range (US, 90-110%; EU, 95-105%). Clinical data demonstrate that patients exposed to higher than recommended doses of bortezomib on the standard twice-weekly dosing schedule are likely to have an increased risk of major toxicities. Bortenat 2-mg vials contained an isovaleraldehyde impurity; the origin of this is unknown. Additionally, the ratio of boronic acid to boronic ester differed between Bortenat 2 mg (0.27:1) and 3.5 mg (0.13:1) and VELCADE (0.10:1) samples reconstituted in saline indicating that the Bortenat product is not equivalent to the VELCADE product.

Nonlinearity and disorder: Classification and stability of nonlinear impurity modes

DEFF Research Database (Denmark)

Sukhorukov, Andrey A.; Kivshar, Yuri S.; Bang, Ole

2001-01-01

We study the effects produced by competition of two physical mechanisms of energy localization in inhomogeneous nonlinear systems. As an example, we analyze spatially localized modes supported by a nonlinear impurity in the generalized nonlinear Schrödinger equation and describe three types of no...... the case of a power-law nonlinearity in detail. We discuss several scenarios of the instability-induced dynamics of the nonlinear impurity modes, including the mode decay or switching to a new stable state, and collapse at the impurity site....

Pfirsch–Schlüter neoclassical heavy impurity transport in a rotating plasma

International Nuclear Information System (INIS)

Belli, E A; Candy, J; Angioni, C

2014-01-01

In this work, we extend previous analytic theories for the neoclassical transport of a trace heavy impurity in a rotating plasma in the Pfirsch–Schlüter regime. The complete diffusive and convective components of the ambipolar particle flux are derived. The solution is valid for arbitrary impurity charge and impurity Mach number and for general geometry. Inclusion of finite main-ion temperature gradient effects is shown in the small ion Mach number limit. A simple interpolation formula is derived for the case of high impurity charge and circular geometry. While an enhancement of the diffusion coefficient is found for order one impurity Mach number, a reduction due to the rotation-driven poloidal asymmetry in the density occurs for very large Mach number. (paper)

Impurities in Tc-99m radiopharmaceutical solution obtained from Mo-100 in cyclotron.

Science.gov (United States)

Tymiński, Zbigniew; Saganowski, Paweł; Kołakowska, Ewa; Listkowska, Anna; Ziemek, Tomasz; Cacko, Daniel; Dziel, Tomasz

2018-04-01

The gamma emitting impurities in 99m Tc solution obtained from enriched molybdenum 100 Mo metallic target after its irradiation in a cyclotron were measured using a high-purity germanium (HPGe) detector. The radioactivity range of tested samples of 99m Tc was rather low, in the range from 0.34 to 2.39 MBq, thus creating a challenge to investigate the standard measurement HPGe system for impurity detection and quantification. In the process of 99m Tc separation from irradiated target the AnaLig® Tc-02 resin, Dionex H + and Alumina A columns were used. Fractions of eluates from various steps of separation process were taken and measured for radionuclidic purity. The overall measurement sensitivity of gamma emitters in terms of minimum detectable activity (MDA) was found at the level of 14-70Bq with emission lines in range of 36 - 1836keV resulting in impurity content range of 6.7 × 10 -4 to 3.4 × 10 -3 % for 93 Tc, 93m Tc, 94 Tc, 94m Tc, 95 Tc, 95m Tc, 96 Tc 96 Nb, 97 Nb, 99 Mo contaminants and 9.4 × 10 -3 % for 97m Tc. The usefulness of the chosen measurement conditions and the method applied to testing the potential contaminators was proved by reaching satisfactory results of MDAs less than the criteria of impurity concentration of all nuclides specified in the European Pharmacopoeia. Copyright © 2017 Elsevier Ltd. All rights reserved.

Extended numerical modeling of impurity neoclassical transport in tokamak edge plasmas

International Nuclear Information System (INIS)

Inoue, H.; Yamoto, S.; Hatayama, A.; Homma, Y.

2016-01-01

Understanding of impurity transport in tokamaks is an important issue in order to reduce the impurity contamination in fusion core plasmas. Recently, a new kinetic numerical scheme of impurity classical/neoclassical transport has been developed. This numerical scheme makes it possible to include classical self-diffusion (CL SD), classical inward pinch (CL IWP), and classical temperature screening effect (CL TSE) of impurity ions. However, impurity neoclassical transport has been modeled only in the case where background plasmas are in the Pfirsch-Schluter (PS) regime. The purpose of this study is to extend our previous model to wider range of collisionality regimes, i.e., not only the PS regime, but also the plateau regime. As in the previous study, a kinetic model with Binary Collision Monte-Carlo Model (BMC) has been adopted. We focus on the modeling of the neoclassical self-diffusion (NC SD) and the neoclassical inward pinch (NC IWP). In order to simulate the neoclassical transport with the BCM, velocity distribution of background plasma ions has been modeled as a deformed Maxwell distribution which includes plasma density gradient. Some test simulations have been done. As for NC SD of impurity ions, our scheme reproduces the dependence on the collisionality parameter in wide range of collisionality regime. As for NC IWP, in cases where test impurity ions and background ions are in the PS and plateau regimes, parameter dependences have been reproduced. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Extended numerical modeling of impurity neoclassical transport in tokamak edge plasmas

Energy Technology Data Exchange (ETDEWEB)

Inoue, H.; Yamoto, S.; Hatayama, A. [Graduate School of Science and Technology, Keio University, Hiyoshi, Yokohama (Japan); Homma, Y. [Graduate School of Science and Technology, Keio University, Hiyoshi, Yokohama (Japan); Research Fellow of Japan Society for the Promotion of Science, Tokyo (Japan)

2016-08-15

Understanding of impurity transport in tokamaks is an important issue in order to reduce the impurity contamination in fusion core plasmas. Recently, a new kinetic numerical scheme of impurity classical/neoclassical transport has been developed. This numerical scheme makes it possible to include classical self-diffusion (CL SD), classical inward pinch (CL IWP), and classical temperature screening effect (CL TSE) of impurity ions. However, impurity neoclassical transport has been modeled only in the case where background plasmas are in the Pfirsch-Schluter (PS) regime. The purpose of this study is to extend our previous model to wider range of collisionality regimes, i.e., not only the PS regime, but also the plateau regime. As in the previous study, a kinetic model with Binary Collision Monte-Carlo Model (BMC) has been adopted. We focus on the modeling of the neoclassical self-diffusion (NC SD) and the neoclassical inward pinch (NC IWP). In order to simulate the neoclassical transport with the BCM, velocity distribution of background plasma ions has been modeled as a deformed Maxwell distribution which includes plasma density gradient. Some test simulations have been done. As for NC SD of impurity ions, our scheme reproduces the dependence on the collisionality parameter in wide range of collisionality regime. As for NC IWP, in cases where test impurity ions and background ions are in the PS and plateau regimes, parameter dependences have been reproduced. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Electromagnetic effects on trace impurity transport in tokamak plasmas

Science.gov (United States)

Hein, T.; Angioni, C.

2010-01-01

The impact of electromagnetic effects on the transport of light and heavy impurities in tokamak plasmas is investigated by means of an extensive set of linear gyrokinetic numerical calculations with the code GYRO [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] and of analytical derivations with a fluid model. The impurity transport is studied by appropriately separating diffusive and convective contributions, and conditions of background microturbulence dominated by both ion temperature gradient (ITG) and trapped electron modes (TEMs) are analyzed. The dominant contribution from magnetic flutter transport turns out to be of pure convective type. However it remains small, below 10% with respect to the E ×B transport. A significant impact on the impurity transport due to an increase in the plasma normalized pressure parameter β is observed in the case of ITG modes, while for TEM the overall effect remains weak. In realistic conditions of high β plasmas in the high confinement (H-) mode with dominant ITG turbulence, the impurity diffusivity is found to decrease with increasing β in qualitative agreement with recent observations in tokamaks. In contrast, in these conditions, the ratio of the total off-diagonal convective velocity to the diagonal diffusivity is not strongly affected by an increase in β, particularly at low impurity charge, due to a compensation between the different off-diagonal contributions.

Nuclear relaxation in semiconductors doped with magnetic impurities

International Nuclear Information System (INIS)

Mel'nichuk, S.V.; Tovstyuk, N.K.

1984-01-01

The temperature and concentration dependences are investigated of the nuclear spin-lattice relaxation time with account of spin diffusion for degenerated and non-degenerated semicon- ductors doped with magnetic impurities. In case of the non-degenerated semiconductor the time is shown to grow with temperature, while in case of degenerated semiconductor it is practically independent of temperature. The impurity concentration growth results in decreasing the spin-lattice relaxation time

Impurity band Mott insulators: a new route to high Tc superconductivity

Directory of Open Access Journals (Sweden)

Ganapathy Baskaran

2008-01-01

Full Text Available Last century witnessed the birth of semiconductor electronics and nanotechnology. The physics behind these revolutionary developments is certain quantum mechanical behaviour of 'impurity state electrons' in crystalline 'band insulators', such as Si, Ge, GaAs and GaN, arising from intentionally added (doped impurities. The present article proposes that certain collective quantum behaviour of these impurity state electrons, arising from Coulomb repulsions, could lead to superconductivity in a parent band insulator, in a way not suspected before. Impurity band resonating valence bond theory of superconductivity in boron doped diamond, recently proposed by us, suggests possibility of superconductivity emerging from impurity band Mott insulators. We use certain key ideas and insights from the field of high-temperature superconductivity in cuprates and organics. Our suggestion also offers new possibilities in the field of semiconductor electronics and nanotechnology. The current level of sophistication in solid state technology and combinatorial materials science is very well capable of realizing our proposal and discover new superconductors.

Impurity incorporation in R.A.D. polysilicon layers and consequences on their electrical properties

International Nuclear Information System (INIS)

Revel, G.; Deschamps, N.; Deville, J.P.; Texier-Hervo, C.; Belouet, C.

1982-01-01

The growth of polysilicon layers by direct freezing of a film on a carbon ribbon by the RAD process goes along with a contamination of the silicon melt by carbon and its compositional impurities. This paper reports on this contamination effect studied mainly by means of neutron activation analyses (NAA) and its consequences on the electrical properties of the layers. The purification of the carbon ribbons in chlorine at high temperatures results in low contamination levels of the melt; NAA evidenced a significant segregation at the growth front, the effective partition coefficients determined being in the 10 - 1 to 10 - 3 range. Even though impurities are shown to impair the device performances, it is concluded that they are not necessarily incorporated in an electrically active form. Finally, AM 1 conversion efficiencies of 12% are reported for RAD cells 4 cm 2 in size. (Auth.)

Edge and Core Impurity Transport Study with Spectroscopic Instruments in LHD

International Nuclear Information System (INIS)

Morita, Shigeru; Goto, Motoshi; Kobayashi, Masahiro; Muto, Sadatsugu; Chowdhuri, Malay Bikas; Chunfeng, Dong; Hangyu, Zhou; Zhengying, Cui; Fujii, Keisuke; Hasuo, Masahiro; Iwamae, Atsushi; Furuzawa, Akihiro; Sakurai, Ikuya; Tawara, Yuzuru; Yinxian, Jie; Baonian, Wan; Zhenwei, Wu; Koubiti, Mohammed; Yamaguchi, Naohiro

2009-01-01

Impurity transport was investigated at both edge and core regions in large helical device (LHD) with developed spectroscopic instruments which can measure one- and two-dimensional distributions of impurities. The edge impurity behavior was studied recently using four carbon resonant transitions in different ionization stages of CIII (977A), CIV (1548A), CV (40.3A) and CVI (33.7A). When the line-averaged electron density, n e , is increased from 1 to 6 x 10 13 cm -3 , the ratio of (CIII+CIV)/n e increases while the ratio of (CV+CVI)/n e decreases. Here, CIII+CIV (CV+CVI) expresses the sum of CIII (CV) and CIV (CVI) intensities. The CIII+CIV indicates the carbon influx and the CV+CVI indicates the emissions through the transport in the ergodic layer. The result thus gives experimental evidence on the impurity screening by the ergodic layer in LHD, which is also supported by a three-dimensional edge particle simulation. The core impurity behavior is also studied in high-density discharges (n e ≤ 1x 10 15 cm -3 ) with multi H 2 -pellets injection. It is found that the ratio of V/D (V: convection velocity, D: diffusion coefficient) decreases after pellet injection and Z eff profile shows a flat one at values of 1.1-1.2. These results confirm no impurity accumulation occurs in high-density discharges. As a result, the iron density, n Fe , is analyzed to be 6 x 10 -7 ( = n Fe /n e ) of which the amount can be negligible as radiation source even in such high-density discharges. One- and two-dimensional impurity distributions from space-resolved VUV and EUV spectrometers newly developed for further impurity transport study are also presented with their preliminary results. (magnetically confined plasma)

Modeling impurity-assisted chain creation in noble-metal break junctions

International Nuclear Information System (INIS)

Di Napoli, S; Thiess, A; Blügel, S; Mokrousov, Y

2012-01-01

In this work we present the generalization of the model for chain formation in break junctions, introduced by Thiess et al (2008 Nano Lett. 8 2144), to zigzag transition-metal chains with s and p impurities. We apply this extended model to study the producibility trends for noble-metal chains with impurities, often present in break junction experiments, namely, Cu, Ag and Au chains with H, C, O and N adatoms. Providing the material-specific parameters for our model from systematic full-potential linearized augmented plane-wave first-principles calculations, we find that the presence of such impurities crucially affects the binding properties of the noble-metal chains. We reveal that both the impurity-induced bond strengthening and the formation of zigzag bonds can lead to a significantly enhanced probability for chain formation in break junctions. (paper)

Corrosion behavior of pyroclore-rich titanate ceramics for plutonium disposition; impurity effects

International Nuclear Information System (INIS)

Bakel, A. J.

1999-01-01

The baseline ceramic contains Ti, U, Ca, Hf, Gd, and Ce, and is made up of only four phases, pyrochlore, zirconolite, rutile, and brannerite. The impurities present in the three other ceramics represent impurities expected in the feed, and result in different phase distributions. The results from 3 day, 90 C MCC-1 tests with impurity ceramics were significantly different than the results from tests with the baseline ceramic. Overall, the addition of impurities to these titanate ceramics alters the phase distributions, which in turn, affects the corrosion behavior

Impurity monitoring by laser-induced fluorescence techniques

International Nuclear Information System (INIS)

Gelbwachs, J.A.

1984-01-01

Laser-induced fluorescence spectroscopy can provide a highly sensitive and selective means of detecting atomic and ionic impurities. Because the photodetector can be physically isolated from the laser-excited region, these techniques can be applied to monitoring in hostile environments. The basic concepts behind fluorescence detection are reviewed. Saturated optical excitation is shown to maximize impurity atom emission yield while mitigating effects of laser intensity fluctuations upon absolute density calibration. Monitoring in high- and low-pressure monitoring environments is compared. Methods to improve detection sensitivity by luminescence background suppression are presented

Classical impurity ion confinement in a toroidal magnetized fusion plasma.

Science.gov (United States)

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.

Mobile Probes in Mobile Learning

DEFF Research Database (Denmark)

Ørngreen, Rikke; Blomhøj, Ulla; Duvaa, Uffe

In this paper experiences from using mobile probes in educational design of a mobile learning application is presented. The probing process stems from the cultural probe method, and was influenced by qualitative interview and inquiry approaches. In the project, the mobile phone was not only acting...... as an agent for acquiring empirical data (as the situation in hitherto mobile probe settings) but was also the technological medium for which data should say something about (mobile learning). Consequently, not only the content of the data but also the ways in which data was delivered and handled, provided...... a valuable dimension for investigating mobile use. The data was collected at the same time as design activities took place and the collective data was analysed based on user experience goals and cognitive processes from interaction design and mobile learning. The mobile probe increased the knowledge base...

First-principles thermodynamic calculations of diffusion characteristics of impurities in γ-iron

International Nuclear Information System (INIS)

Tsuru, T.; Kaji, Y.

2013-01-01

Because solute impurities have an effect on embrittlement through segregation under irradiation, solute stability and the influence of irradiation on the diffusion characteristics of impurities become prominent due to several acceleration effects of high irradiance circumstances in irradiated materials. In this study, the diffusion characteristics of several impurities in non-magnetic fcc iron are investigated using first-principles density functional theory (DFT) calculations. In accordance with classical diffusion and transition state theories, we nonempirically evaluated the contribution to properties of the binding energy between vacancy and each impurity and the migration enthalpy. The migration energy was calculated using the nudged elastic band method with DFT. The vacancy formation energy, including the entropic contributions to free energies in γ-iron, was evaluated by considering vibrational phonon frequencies based on frozen phonons employing the harmonic approximation for the lattice dynamics. Consequently, we confirmed that the binding energy between large-radius impurities and vacancies is larger than that with an equivalent size of the solvent element, and that the migration enthalpies of these impurities are quite small compared with self diffusion. This finding may indicate that the electronic binding states at the saddle point have a large influence on the migration of impurities

Strongly correlated impurity band superconductivity in diamond: X-ray spectroscopic evidence

Directory of Open Access Journals (Sweden)

G. Baskaran

2006-01-01

Full Text Available In a recent X-ray absorption study in boron doped diamond, Nakamura et al. have seen a well isolated narrow boron impurity band in non-superconducting samples and an additional narrow band at the chemical potential in a superconducting sample. We interpret the beautiful spectra as evidence for upper Hubbard band of a Mott insulating impurity band and an additional metallic 'mid-gap band' of a conducting 'self-doped' Mott insulator. This supports the basic framework of a recent theory of the present author of strongly correlated impurity band superconductivity (impurity band resonating valence bond, IBRVB theory in a template of a wide-gap insulator, with no direct involvement of valence band states.

The effects of naturally occurring impurities in rock salt

Indian Academy of Sciences (India)

In this paper we investigate the effect that naturally occurring impurities in salt mines have both on effective permittivity of the medium and on radio wave propagation at ∼200 MHz. The effective permittivity is determined based on the dielectric properties of salt and the characteristics of the main impurities. We conclude that ...

The effect of iron and copper impurities on the wettability of sphalerite (110) surface.

Science.gov (United States)

Simpson, Darren J; Bredow, Thomas; Chandra, Anand P; Cavallaro, Giuseppe P; Gerson, Andrea R

2011-07-15

The effect of impurities in the zinc sulfide mineral sphalerite on surface wettability has been investigated theoretically to shed light on previously reported conflicting results on sphalerite flotation. The effect of iron and copper impurities on the sphalerite (110) surface energy and on the water adsorption energy was calculated with the semi-empirical method modified symmetrically orthogonalized intermediate neglect of differential overlap (MSINDO) using the cyclic cluster model. The effect of impurities or dopants on surface energies is small but significant. The surface energy increases with increasing surface iron concentration while the opposite effect is reported for increasing copper concentration. The effect on adsorption energies is much more pronounced with water clearly preferring to adsorb on an iron site followed by a zinc site, and copper site least favorable. The theoretical results indicate that a sphalerite (110) surface containing iron is more hydrophilic than the undoped zinc sulfide surface. In agreement with the literature, the surface containing copper (either naturally or by activation) is more hydrophobic than the undoped surface. Copyright © 2011 Wiley Periodicals, Inc.

Size, Shape and Impurity Effects on Superconducting critical temperature.

Science.gov (United States)

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.

Effect of impurities on kinetic transport processes in fusion plasmas

Energy Technology Data Exchange (ETDEWEB)

Braun, Stefanie

2010-12-10

Within the framework of this thesis, different problems arising in connection with impurities have been investigated. Collisional damping of zonal flows in tokamaks: Since the Coulomb collision frequency increases with increasing ion charge, heavy, highly charged impurities play an important role in this process. The effect of such impurities on the linear response of the plasma to an external potential perturbation, as caused by zonal flows, is calculated with analytical methods. In comparison with a pure plasma, the damping of the flows occurs, as expected, considerably faster; for experimentally relevant parameters, the enhancement exceeds the effective charge Z{sub eff} of the plasma. Impurity transport driven by microturbulence in tokamaks: With regard to impurities, it is especially important whether the resulting flows are directed inwards or outwards, since they are deleterious for core energy confinement on the one hand, but on the other hand help protecting plasma-facing components from too high energy fluxes in the edge region. A semi-analytical model is presented describing the resulting impurity fluxes and the stability boundary of the underlying mode. The main goal is to bridge the gap between, on the one hand, costly numerical simulations, which are applicable to a broad range of problems but yield scarcely traceable results, and, on the other hand, analytical theory, which might ease the interpretation of the results but is so far rather rudimentary. The model is based on analytical formulae whenever possible but resorts to a numerical treatment when the approximations necessary for an analytical solution would lead to a substantial distortion of the results. Both the direction of the impurity flux and the stability boundary are found to depend sensitively on the plasma parameters such as the impurity density and the temperature gradient. Pfirsch-Schlueter transport in stellarators: Due to geometry effects, collisional transport plays a much more

Soliton scatterings by impurities in a short-length sine-Gordon chain

International Nuclear Information System (INIS)

Dikande, A.M.; Kofane, T.C.

1995-07-01

The scattering of soliton by impurities at the frontiers of a finite-length region of an infinite sine-Gordon chain is analyzed. The impurities consist of two isotopic inhomogeneities installed at the boundaries of the finite-length region. The soliton solution in the region is found in term of snoidal sine-Gordon soliton which properly takes into account the effects of the boundaries. By contrast, the soliton solutions in the neighboring sides of the region are obtained in terms of the so-called large-amplitude, localized kinks with limiting spatial extensions at x → ± ∞, which is equal ±π. Using the continuity of these soliton solutions at the frontiers as well as appropriate boundary conditions, it is shown that the soliton may be either i) reflected by the incident impurity; ii) trapped (with oscillating motions) between the two impurities (i.e. inside the infinite region); or iii) transmitted by the second impurity into the third, infinitely extended region. The threshold velocities for the reflection and transmission into different regions are found and shown to vary exponentially as a function of the length of the bounded region. The frequency of soliton oscillations between the impurities has also been calculated in some acceptable limit. (author). 28 refs, 1 fig

Models for impurity production and transport in tokamaks

International Nuclear Information System (INIS)

Hogan, J.T.

1976-01-01

Models for the edge conditions which are commonly used in tokamak transport codes have been kept simple partly because of a lack of data. A report is presented on an improved model for the particle and energy balance of e - , H 1 + , H 1 0 , H 2 + , H 2 0 , O 0 , O/sup (1 yields 8) + / in the plasma scrape-off region. Experiments should yield the needed data in the near future, and allow one to test the model. The diffusion of impurities has been studied with a neoclassical model. The role of 'anomalous spreading' of the impurity distribution has been studied for the case of Fe. A model is presented for the expulsion of low-Z (oxygen) impurities for cases where q(0) greater than 1, but in which a large shear-free region is produced in the plasma core

Impurity sources in TEXTOR

Energy Technology Data Exchange (ETDEWEB)

Pospieszczyk, A; Bay, H L; Bogen, P; Hartwig, H; Hintz, E; Koenen, L; Ross, G G; Rusbueldt, D; Samm, U; Schweer, B

1987-02-01

The deuterium, oxygen and carbon fluxes from the main limiter and the deuterium fluxes from the wall are measured in TEXTOR for an 'all carbon' surrounding as a function of central density n/sub e/, of applied ICRH-power and of different wall conditions (carbonization). For this purpose, emission spectroscopy both with filter systems and spectrometers has been used. It is found that a major release mechanism for light impurities is via the formation of molecules. Oxygen seems to enter the discharge from the liner via O-D containing molecules, whereas the limiter acts as the main carbon source by the release of hydro-carbons as indicated by the observed CD-band spectra. Both oxygen and carbon fluxes are reduced by about a factor of two after a fresh carbonization. Above a certain critical density the plasma detaches from the limiter and forms a stable discharge with a radiation cooled boundary layer and with a major fraction of particles now reaching the wall instead of the limiter. The critical density rises with decreasing impurity fluxes or with increasing heating powers.

Impurity sources in TEXTOR

International Nuclear Information System (INIS)

Pospieszczyk, A.; Bay, H.L.; Bogen, P.; Hartwig, H.; Hintz, E.; Koenen, L.; Ross, G.G.; Rusbueldt, D.; Samm, U.; Schweer, B.

1987-01-01

The deuterium, oxygen and carbon fluxes from the main limiter and the deuterium fluxes from the wall are measured in TEXTOR for an 'all carbon' surrounding as a function of central density n e , of applied ICRH-power and of different wall conditions (carbonization). For this purpose, emission spectroscopy both with filter systems and spectrometers has been used. It is found that a major release mechanism for light impurities is via the formation of molecules. Oxygen seems to enter the discharge from the liner via O-D containing molecules, whereas the limiter acts as the main carbon source by the release of hydro-carbons as indicated by the observed CD-band spectra. Both oxygen and carbon fluxes are reduced by about a factor of two after a fresh carbonization. Above a certain critical density the plasma detaches from the limiter and forms a stable discharge with a radiation cooled boundary layer and with a major fraction of particles now reaching the wall instead of the limiter. The critical density rises with decreasing impurity fluxes or with increasing heating powers. (orig.)

A crystalline cluster method for deep impurities in insulators

International Nuclear Information System (INIS)

Guimaraes, P.S.

1983-01-01

An 'ab initio' self-consistent-field crystalline-cluster approach to the study of deep impurity states in insulators is proposed. It is shown that, in spite of being a cluster calculation, the interaction of the impurity with the crystal environment is fully taken into account. It is also shown that the present representation of the impurity states is, at least, as precise as the crystalline cluster representation of the pure crystal electronic structure. The procedure has been tested by performing the calculation of the electronic structure of the U center in a sodium chloride crystal, and it has been observed that the calculated GAMMA 1 - GAMMA 15 absorption energy is in good agreement with experiment. (Author) [pt

A crystalline cluster method for deep impurities in insulators

International Nuclear Information System (INIS)

Guimaraes, P.S.

1983-01-01

An ''ab initio'' self-consistent-field crysttalline-cluster approach to the study of deep impurity states in insulators is proposed. It is shown that, in spite of being a cluster calculation, the interaction of the impurity with the crystal environment is fully taken into account. It is also shown that the present representation of the impurity states is, at least, as precise as the crystalline cluster representation of the pure crystal electronic structure. The procedure has been tested by performing the calculation of the electronic structure of the U center in a sodium chloride crystal, and it has been observed that the calculated γ 1 - γ 15 absorption energy is in good agreement with experiment. (author) [pt

Experimental and gyrokinetic investigation of core impurity transport in Alcator C-mod

Science.gov (United States)

Howard, N.; Greenwald, M.; Podpaly, Y.; Reinke, M. L.; Rice, J. E.; White, A. E.; Mikkelsen, D. R.; Puetterich, T.

2010-11-01

A new multiple pulse laser blow-off system coupled with an upgraded high resolution x-ray spectrometer with spatial resolution allow for the most detailed studies of impurity transport on Alcator C-mod to date. Trace impurity injections created by the laser blow-off technique were introduced into plasmas with a wide range of parameters and time evolving profiles of He-like calcium were measured. The unique measurement of a single charge state profile and line integrated emission measurements from spectroscopic diagnostics were compared with the simulated emission from the impurity transport code STRAHL. A nonlinear least squares fitting routine was coupled with STRAHL, allowing for core impurity transport coefficients with errors to be determined. With this method, experimental data from trace calcium injections were analyzed and radially dependent, core values (< r/a ˜.6) of the diffusive and convective components of the impurity flux were obtained. The STRAHL results are compared with linear and global, nonlinear simulations from the gyrokinetic code GYRO. Results of this comparison and an investigation of the underlying physics associated with turbulent impurity transport will be presented.

Engineering and material aspects of impurity control systems

International Nuclear Information System (INIS)

Koski, J.A.

1985-01-01

The design of impurity control devices for fusion energy devices is discussed from the engineering and materials viewpoint. First, examples of impurity control devices are presented, and the plasma edge environment for which they are designed is briefly described. Materials concerns related to the design of the components are discussed and some currently proposed designs presented. Engineering tools available to the designer are listed, and some commonly encountered engineering analysis problems described

Method of plasma impurity control without magnetic divertor

International Nuclear Information System (INIS)

Schivell, J.F.

1977-06-01

A method is proposed for controlling impurity generation in a tokomak by skimming and pumping the scrape-off. This method avoids many of the complications of a magnetic divertor, such as specially configured magnetic fields, toroidal symmetry, and inefficient use of toroidal field volume. Estimates are given for operating parameters. Impurity reductions of as much as a factor of 10 should be achievable. The necessary high-capacity pump would employ either titanium gettering or cryocondensation

Analysis of impurities at trace levels in metallic niobium by instrumental neutron activation analysis

International Nuclear Information System (INIS)

Favaro, D.I.T.; Vasconcellos, M.B.A.; Santos, C.

1989-10-01

The interest in obtaining niobium of high purity has increased due to the recent applications of this material in both vacuum and high temperature technologies and to its potential uses in the aeronautic and aerospacial industries and in the nuclear energy field. In the present work, a procedure of analysis of impurities in the parts per million level, in eletrolitic and non-eletrolitic niobium samples has been established. The method of neutron activation analysis followed by high resolution gamma ray spectrometry has been used. The elements Al, Na, Mn, Cl and In, in ppm level and Y, in the percentage level, were determined after irradiation from 1 to 20 minutes, under a thermal neutron flux of 10 11 n.cm -2 .s -1 at the IEA-Rl reactor of the IPEN-CNEN/SP. The γ-rays from the radioactive products were measured with a Ge(Li) detector coupled to a 4096 channel analyzer. The elements Ta, Cr and W, in the parts per million level, were determined with irradiation of 8 hours under a thermal neutron flux of 10 12 n.cm -2 .s -1 . (autor) [pt

Stability-Indicating RP-UPLC Method for the Simultaneous Determination of Potential Degradation and Process Impurities of Amlodipine Basylate and Benazepril HCl in Pharmaceutical Dosage Form

Directory of Open Access Journals (Sweden)

Gajanan B. Kasawar

2014-10-01

Full Text Available A stability-indicating RP-UPLC method was developed for the quantification of related impurities of amlodipine basylate (AB and Benazepril hydrochloride (BH in solid pharmaceutical dosages form. The chromatographic separation employs a C18 column using a gradient elution, being solvent-A (1.36 g of potassium dihydrogen phosphate dissolved in one liter of water, adjusted to pH 3.0 with orthophosphoric acid and solvent-B (acetonitrile delivered at a flow rate of 0.3 mL min-1. The analytes were detected and quantified at 217 nm and 240 nm using photo diode-array detector. The method was validated demonstrating to be accurate and precise within the corresponding linear range of all components. The stability of the method was investigated under different stress conditions including hydrolytic, oxidative, exposed to photolytic, humidity and thermal as recommended by ICH guidelines. Relevant degradation was found under hydrolytic and oxidative conditions. Robustness against small modification in mobile phase pH, column oven temperature, flow rate and percentage of the mobile phase composition was ascertained. Lower limit of quantification and detection was also determined. The peak purity indices (purity angle < purity threshold obtained with the aid of PDA detector and satisfactory resolution between related impurities established the specificity of the determination.

On the photo-ionization of impurity centres in semiconductors

International Nuclear Information System (INIS)

Tomak, M.

1982-10-01

The dependence of the photo-ionization cross-section on photon energy is calculated. The impurity potential is assumed to be of the Hulthen potential type and bound state wave function is calculated variationally. The results show that, at least in some cases, the Hulthen potential may describe the impurity better than the hydrogen or delta function potentials. (author)