Source Of Impurities Research Articles

First results with 3-strap ICRF antennas in ASDEX Upgrade

The 3-strap antennas in ASDEX Upgrade allow ICRF operation with low tungsten (W) content in the confined plasma with W-coated antenna limiters. With the 3-strap antenna configuration, the local W impurity source at the antenna is drastically reduced and the core W concentration is similar to that of the boron coated 2-strap antenna at a given ICRF power. Operation of the 3-strap antennas with the power ratio between the central and the outer straps of and is adopted to minimize the ICRF-specific W release.

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

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

A Small-scale Model to Assess the Risk of Leachables from Single-use Bioprocess Containers through Protein Quality Characterization.

Leachables from single-use systems often exist in small quantities and are difficult to detect with existing analytical methods. The presence of relevant detrimental leachables from single-use bioprocess containers (BPCs) can be indirectly detected by studying the stability of monoclonal antibodies via changes by size exclusion chromatography, capillary electrophoresis sodium dodecyl sulfate, and visible/sub-visible particles using a small-scale stress model containing high surface area-to-volume ratio at elevated temperature alongside with an appropriate control (e.g., glass vials or stainless steel containers). These changes in protein quality attributes allowed the evaluation of potential risks associated with adopting single-use bioprocess containers for storage as well as bag quality and bag differences between earlier and later batches. These leachables appear to be generated during the bag sterilization process by gamma irradiation. Improvements in protein stability after storage in "preheated" bags indicated that these leachables may be thermally unstable or volatile. The effect of surfactant levels, storage temperatures, surface area-to-volume ratios, filtration, and buffer exchange on leachables and protein stability were also assessed.

‘From an Impure Source, All Is Impure’: The Rise and Fall of Andrija Štampar’s Public Health Eugenics in Yugoslavia

‘From an Impure Source, All Is Impure’: The Rise and Fall of Andrija Štampar’s Public Health Eugenics in Yugoslavia

EMC3-EIRENE modelling of edge impurity transport in the stochastic layer of the large helical device compared with extreme ultraviolet emission measurements

The transport properties and line emissions of carbon impurity in the stochastic layer of the Large Helical Device have been investigated with the 3D edge transport code EMC3-EIRENE. A parameter study has been performed to examine the sensitivity of the simulation results on each transport term in the impurity transport model and the impurity source characteristics, i.e. the source amount and the location. The modelling has revealed that in order to reproduce the experimental results of the emission distribution, the impurity perpendicular transport coefficient (Dimp) and the first wall source play important roles, while changes to the ion thermal and the friction forces are rather irrelevant. The detailed study of flux tube tracing and magnetic field structure in the edge stochastic layer, in relation to impurity transport, has shown that the deeper penetration of impurity into the higher plasma density region due to the enhanced Dimp and the first wall source is responsible for the change of emission pattern as well as the intensity. The analysis indicates that Dimp might be larger than that of background plasma by a few factors and also that there probably exists a substantial amount of first wall impurity source.

Electrochemical Deposition of CdTe Semiconductor Thin Films for Solar Cell Application Using Two-Electrode and Three-Electrode Configurations: A Comparative Study

Thin films of CdTe semiconductor were electrochemically deposited using two-electrode and three-electrode configurations in potentiostatic mode for comparison. Cadmium sulphate and tellurium dioxide were used as cadmium and tellurium sources, respectively. The layers obtained using both configurations exhibit similar structural, optical, and electrical properties with no specific dependence on any particular electrode configuration used. These results indicate that electrochemical deposition (electrodeposition) of CdTe and semiconductors in general can equally be carried out using two-electrode system as well as the conventional three-electrode system without compromising the essential qualities of the materials produced. The results also highlight the advantages of the two-electrode configuration in process simplification, cost reduction, and removal of a possible impurity source in the growth system, especially as the reference electrode ages.

Ultrahigh mobility in polyolefin-supported graphene

A high carrier mobility is an important parameter for graphene-based electronics. While the recent reports have shown impressive results for individual micro-scale devices, scalable production of high mobility graphene has been challenging. We here show that centimeter-scale graphene devices with room temperature carrier mobilities in excess of 10 000 cm(2) V(-1) s(-1) can be achieved on polyolefinic substrates. Measurements on Parafilm-supported graphene devices show, on average, a fivefold-enhancement in mobility over traditional devices. We find that a decreased charged-impurity scattering is the origin of this behavior. Spectroscopic characterization reveals oxygen-containing polymer residue as the main source of such charged impurities. A comparison of different polyolefins highlights the positive impact of oxygen-free polymers as support materials for high mobility graphene devices. Finally, moldable and wearable graphene devices for biosensors were shown to be enabled by polyolefinic substrates.

Understanding metastable phase transformation during crystallization of RDX, HMX and CL-20: experimental and DFT studies.

Multiphase growth during crystallization severely affects deliverable output of explosive materials. Appearance and incomplete transformation of metastable phases are a major source of polymorphic impurities. This article presents a methodical and molecular level understanding of the metastable phase transformation mechanism during crystallization of cyclic nitramine explosives, viz. RDX, HMX and CL-20. Instantaneous reverse precipitation yielded metastable γ-HMX and β-CL-20 which undergo solution mediated transformation to the respective thermodynamic forms, β-HMX and ε-CL-20, following 'Ostwald's rule of stages'. However, no metastable phase, anticipated as β-RDX, was evidenced during precipitation of RDX, which rather directly yielded the thermodynamically stable α-phase. The γ→β-HMX and β→ε-CL-20 transformations took 20 and 60 minutes respectively, whereas formation of α-RDX was instantaneous. Density functional calculations were employed to identify the possible transition state conformations and to obtain activation barriers for transformations at wB97XD/6-311++G(d,p)(IEFPCM)//B3LYP/6-311G(d,p) level of theory. The computed activation barriers and lattice energies responsible for transformation of RDX, HMX and CL-20 metastable phases to thermodynamic ones conspicuously supported the experimentally observed order of phase stability. This precise result facilitated an understanding of the occurrence of a relatively more sensitive and less dense β-CL-20 phase in TNT based melt-cast explosive compositions, a persistent and critical problem unanswered in the literature. The crystalline material recovered from such compositions revealed a mixture of β- and ε-CL-20. However, similar compositions of RDX and HMX never showed any metastable phase. The relatively long stability with the highest activation barrier is believed to restrict complete β→ε-CL-20 transformation during processing. Therefore a method is suggested to overcome this issue.

Ball-milled sulfur-doped graphene materials contain metallic impurities originating from ball-milling apparatus: their influence on the catalytic properties.

Graphene materials have found applications in a wide range of devices over the past decade. In order to meet the demand for graphene materials, various synthesis methods are constantly being improved or invented. Ball-milling of graphite to obtain graphene materials is one of the many versatile methods to easily obtain bulk quantities. In this work, we show that the graphene materials produced by ball-milling are spontaneously contaminated with metallic impurities originating from the grinding bowls and balls. Ball-milled sulfur-doped graphene materials obtained from two types of ball-milling apparatus, specifically made up of stainless steel and zirconium dioxide, were investigated. Zirconium dioxide-based ball-milled sulfur-doped graphene materials contain a drastically lower amount of metallic impurities than stainless steel-based ball-milled sulfur-doped graphene materials. The presence of metallic impurities is demonstrated by their catalytic effects toward the electrochemical catalysis of hydrazine and cumene hydroperoxide. The general impression toward ball-milling of graphite as a versatile method for the bulk production of 'metal-free' graphene materials without the need for post-processing and the selection of ball-milling tools should be cautioned. These findings would have wide-reaching implications for graphene research.

Highly integrated CO2capture and conversion: direct synthesis of cyclic carbonates from industrial flue gas

The ability of early transition metal halides to capture and convert CO2from diluted gas flows has been exploited in the cycloaddition of CO2to epoxides using industrial flue gas as an impure source of CO2.

Nanoparticle Ligands and Pyrolized Graphitic Carbon in CZTSSe Photovoltaic Devices

Thin-film photovoltaic (PV) devices can be fabricated using a solution-based synthesis procedure in which metal-chalcogenide nanocrystals with aliphatic coordinating ligands are suspended in a solvent to produce a printable ink (NC-ink). However, the aliphatic ligands that are used to solubilize and stabilize the nanocrystals operate as a significant source of carbon impurities that are incorporated into the final device absorber layer. Despite the ubiquity of this technique and the fact that carbon defects have been reported to be found across a spectrum of devices, the structure, properties, and influence of the carbon on PV device performance remain relatively unexplored. Our findings indicate that these organic ligands undergo a pyrolysis reaction during annealing, producing an electrically conductive, graphitic carbon that also reacts with chalcogens (S or Se) to produce heterocyclic moieties. In this work, we used oleylamine (OLA) and dodecylamine (DDA) to fabricate Cu2ZnSn(SxSe1–x)4 (CZTSSe) photov...

Modelling of the influence of entrained and dissolved air on the performance of an oil-hydraulic capacity

Fluids used in fluid power systems to transmit power and energy seldom consist of pure oil due to a large number of impurity sources. Especially impurities in form of air bubbles highly change the system behaviour with respect to stiffness and efficiency. The aim of this paper is to provide a mathematical model to simulate the effect of air on the pressure build-up and release in an oil-hydraulic capacity. Therefore, first a model to calculate the mass transfer between dissolved and entrained air is presented. In the end, the new developed model is validated with measurements.

Mechanical intermixing of elements and self-organization of (FeNi) and (CoFeNi) nanostructured composite layers on a Ti sheet under ball collisions

A Ti sheet was subjected to intense plastic deformation through ball collisions initiated in a mechanically vibrated vial. The Ti was cut into a disk shape and fixed on one side of the vial with either Ni or Co disks fixed on the opposite side. The objective here was to intentionally use the Ni and Co disks as a source of Ni and Co impurities, while steel balls were to serve as a source for Fe impurities. During processing, ball collisions continuously introduced impurities from the grinding media onto the Ti surface, caused strong material flow, and induced mechanical intermixing of the elements, resulting in self-organization of the polycrystalline nanocomposite structure with an average grain size of about 8 nm. The phase composition of the alloyed layers was dependent on the material transferred into the system. When both Ti and Ni disks were subjected to ball collisions, the alloyed layer was composed of fcc (Fe,Ni) and Ti grains. However, when the Ni disk was subsequently replaced with Co, the layer consisted of bcc and fcc CoFeNi along with Ti grains. The fcc (Fe,Ni) phase was formed on the basis of the fcc Ni crystal structure, while the bcc Fe structure served as the basis for the bcc CoFeNi phase. The as-fabricated nanocomposite layers were extremely hard (∼900 HV on the average), and a nearly three-fold increase was observed in the surface hardness of the Ti sheet after processing. The as-fabricated layers exhibited magnetic properties representative of soft-magnetic materials.

Study of carbon transport in the scrape-off layer of HL-2A with impurity sources located at limiter, dome, and divertor

Impurity transport in the scrape-off layer (SOL) has been studied in ohmically heated discharges of the HL-2A tokamak based on space-resolved vacuum ultraviolet spectroscopy. The vertical profile (from the plasma center to the lower X-point) of carbon emissions of CIII (977 Å: 2s2 1S0-2s2p ) and CIV (1548 Å: 2s 2S-2p 2P) as well as the ratio of CIV to CIII were measured to investigate the edge impurity transport with relation to impurity source locations and sputtering characteristics. The experimental result shows that the impurity profile in the SOL has been clearly changed against different source locations. The emission of CIII and CIV from the mid-plane is stronger than that from the X-point when the impurity source is located at the divertor plate. The profile becomes flat as a result. When the impurity source changes to the dome source, the profile clearly changes to a slightly peaked one, indicating the edge carbon emission at the X-point is stronger than the mid-plane. The change to the limiter source makes the profile further peaked by increasing the carbon emission at the X-point. In the case of the dome impurity source, the intensity of CIII/ne and CIV/ne, normalized to line-averaged electron density, ne, decreases with ne at low ne (ne ⩽ 2.6 × 1019 m−3) and becomes saturated at high ne (ne > 2.6 × 1019 m−3). In contrast, the ratio of CIV to CIII increases with ne at low ne and starts to decrease at high ne. A numerical simulation with 3D edge plasma transport code, EMC3-EIRENE, suggests that a poloidal asymmetry in the impurity flow profile and an enhanced physical sputtering play an important role in the edge impurity distribution, particularly in the screening efficiency of C2+ and C3+ ions in the SOL region of the HL-2A tokamak.

Co-ion fluxes of simple inorganic ions in electrodialysis metathesis and conventional electrodialysis

The main functionality of ion-exchange membranes is to selectively permeate either cations or anions. However, co-ions may permeate as well to some extent through these membranes. For the production of chemicals with electrodialysis metathesis and conventional electrodialysis, these co-ion fluxes are a major source of impurities in the produced chemicals. The present paper studies the co-ion fluxes and the influence of operating parameters. The results clearly indicate that co-ion fluxes are predominately determined by the difference in ion concentration across the membrane. A more than linear increase in co-ion flux with respect to the ion concentration was observed. The current density has no significant influence on the co-ion fluxes. Therefore, a high current density leads to a smaller transport number of co-ions and improves the product purity in electrodialysis metathesis. Moreover, the co-ion flux can be decreased by the use of bulky counter-ions. In a conventional electrodialysis configuration, cation impurities are mainly caused by a diffusional flux. This flux is approximately three times larger than the co-ion flux. In contrast, the anion impurities are predominantly initiated by a co-ion flux and in magnitude smaller than the cation impurities.

Transport in indium-decorated graphene

The electronic transport properties of single layer graphene having a dilute coating of indium adatoms has been investigated. Our studies establish that isolated indium atoms donate electrons to graphene and become a source of charged impurity scattering, affecting the conductivity as well as magnetotransport properties of the pristine graphene. Notably, a positive magnetoresistance is observed over a wide density range after In doping. The low field magnetoresistance carries signatures of quantum interference effects which are significantly altered by the adatoms.

Graded-Bandgap Solar Cells Using All-Electrodeposited ZnS, CdS and CdTe Thin-Films

A 3-layer graded-bandgap solar cell with glass/FTO/ZnS/CdS/CdTe/Au structure has been fabricated using all-electrodeposited ZnS, CdS and CdTe thin layers. The three semiconductor layers were electrodeposited using a two-electrode system for process simplification. The incorporation of a wide bandgap amorphous ZnS as a buffer/window layer to form glass/FTO/ZnS/CdS/CdTe/Au solar cell resulted in the formation of this 3-layer graded-bandgap device structure. This has yielded corresponding improvement in all the solar cell parameters resulting in a conversion efficiency >10% under AM1.5 illumination conditions at room temperature, compared to the 8.0% efficiency of a 2-layer glass/FTO/CdS/CdTe/Au reference solar cell structure. These results demonstrate the advantages of the multi-layer graded-bandgap device architecture over the conventional 2-layer structure. In addition, they demonstrate the effective application of the two-electrode system as a simplification to the conventional three-electrode system in the electrodeposition of semiconductors with the elimination of the reference electrode as a possible impurity source.

Beryllium migration in JET ITER-like wall plasmas

JET is used as a test bed for ITER, to investigate beryllium migration which connects the lifetime of first-wall components under erosion with tokamak safety, in relation to long-term fuel retention. The (i) limiter and the (ii) divertor configurations have been studied in JET-ILW (JET with a Be first wall and W divertor), and compared with those for the former JET-C (JET with carbon-based plasma-facing components (PFCs)). (i) For the limiter configuration, the Be gross erosion at the contact point was determined in situ by spectroscopy as between 4% (Ein = 35 eV) and more than 100%, caused by Be self-sputtering (Ein = 200 eV). Chemically assisted physical sputtering via BeD release has been identified to contribute to the effective Be sputtering yield, i.e. at Ein = 75 eV, erosion was enhanced by about 1/3 with respect to the bare physical sputtering case. An effective gross yield of 10% is on average representative for limiter plasma conditions, whereas a factor of 2 difference between the gross erosion and net erosion, determined by post-mortem analysis, was found. The primary impurity source in the limiter configuration in JET-ILW is only 25% higher (in weight) than that for the JET-C case. The main fraction of eroded Be stays within the main chamber. (ii) For the divertor configuration, neutral Be and BeD from physically and chemically assisted physical sputtering by charge exchange neutrals and residual ion flux at the recessed wall enter the plasma, ionize and are transported by scrape-off layer flows towards the inner divertor where significant net deposition takes place. The amount of Be eroded at the first wall (21 g) and the Be amount deposited in the inner divertor (28 g) are in fair agreement, though the balancing is as yet incomplete due to the limited analysis of PFCs. The primary impurity source in the JET-ILW is a factor of 5.3 less in comparison with that for JET-C, resulting in lower divertor material deposition, by more than one order of magnitude. Within the divertor, Be performs far fewer re-erosion and transport steps than C due to an energetic threshold for Be sputtering, and inhibits as a result of this the transport to the divertor floor and the pump duct entrance. The target plates in the JET-ILW inner divertor represent at the strike line a permanent net erosion zone, in contrast to the net deposition zone in JET-C with thick carbon deposits on the CFC (carbon-fibre composite) plates. The Be migration identified is consistent with the observed low long-term fuel retention and dust production with the JET-ILW.

Fabrication of ultrathin impurity source to minimize radiation-induced losses in photosensitive films of CdS

The formation of a lead arachidate film was studied at interfaces of an aqueous solution of lead nitrate with the air and with a solid hydrophilic substrate. The efficiency of lead transfer onto a semiconductor substrate by the horizontal lift method was estimated. Optimal conditions of the fabrication of lead arachidate monolayers with minimum oxygen content were found in order to use these layers as an impurity source for CdS. It was shown that an optimal relationship between the photosensitivity of CdS films and losses induced by accelerated electrons is attained due to the formation of PbS precipitates with the radius of at least 3 nm in a topmost layer with the thickness of about the depth of maximal energy dissipation of the ionizing radiation.

Poloidal asymmetries in edge transport barriers

Measurements of impurities in Alcator C-Mod indicate that in the pedestal region, significant poloidal asymmetries can exist in the impurity density, ion temperature, and main ion density. In light of the observation that ion temperature and electrostatic potential are not constant on a flux surface [Theiler et al., Nucl. Fusion 54, 083017 (2014)], a technique based on total pressure conservation to align profiles measured at separate poloidal locations is presented and applied. Gyrokinetic neoclassical simulations with XGCa support the observed large poloidal variations in ion temperature and density, and that the total pressure is approximately constant on a flux surface. With the updated alignment technique, the observed in-out asymmetry in impurity density is reduced from previous publishing [Churchill et al., Nucl. Fusion 53, 122002 (2013)], but remains substantial (nz,H/nz,L∼6). Candidate asymmetry drivers are explored, showing that neither non-uniform impurity sources nor localized fluctuation-driven transport are able to explain satisfactorily the impurity density asymmetry. Since impurity density asymmetries are only present in plasmas with strong electron density gradients, and radial transport timescales become comparable to parallel transport timescales in the pedestal region, it is suggested that global transport effects relating to the strong electron density gradients in the pedestal are the main driver for the pedestal in-out impurity density asymmetry.