Abstract
A comparative study of nitrogen versus neon has been carried out to analyze the impact of the two radiative species on power dissipation, SOL impurity distribution, divertor and pedestal ...characteristics. The experimental results show that N remains compressed in the divertor, thereby providing high radiative losses without affecting the pedestal profiles and displacing carbon as dominant radiator. Neon, instead, radiates more upstream than N thus reducing the power flux through the separatrix leading to a reduced ELM frequency and compression in the divertor. A significant amount of neon is measured in the plasma core leading to a steeper density gradient. The different behavior between the two impurities is confirmed by SOLPS-ITER modeling which for the first time at DIII-D includes multiple impurity species and a treatment of full drifts, currents and neutral–neutral collisions. The impurity transport in the SOL is studied in terms of the parallel momentum balance showing that N is mostly retained in the divertor whereas Ne leaks out consistent with its higher ionization potential and longer mean free path. This is also in agreement with the enrichment factor calculations which indicate lower divertor enrichment for neon. The strong ionization source characterizing the SAS divertor causes a reversal of the main ions and impurity flows. The flow reversal together with plasma drifts and the effect of the thermal force contribute significantly in the shift of the impurity stagnation point affecting impurity leakage. This work provides a demonstration of the impurity leakage mechanism in a closed divertor structure and the consequent impact on pedestal. Since carbon is an intrinsic radiator at DIII-D, in this paper we have also demonstrated the different role of carbon in the N vs Ne seeded cases both in the experiments and in the numerical modeling. Carbon contributes more when neon seeding is injected compared to when nitrogen is used. Finally, the results highlight the importance of accompanying experimental studies with numerical modeling of plasma flows, drifts and ionization profile to determine the details of the SOL impurity transport as the latter may vary with changes in divertor regime and geometry. In the cases presented here, plasma drifts and flow reversal caused by high level of closure in the slot upper divertor at DIII-D play an important role in the underlined mechanism.
This paper investigates an analytical and numerical study on impurity–impurity and impurity–breather interactions associated with energy localization in a quantum 1D Klein–Gordon chain. The nonlinear ...Schrödinger equation (NLSE) is obtained with the use of Glauber’s coherent states in addition to a multiple time scale method. The resonant structures are found via the frequency spectrum around the critical impurity mass. The condition of existence of breather and impure localized mode are acquired. The dynamics of the impurity mode can be significantly controlled by the impurity mass. The accuracy of the analytical approach is validated by an excellent agreement with the finding of numerical simulation. When the breather interacts with two impure modes, several behaviors such as trapping, chaotic trapping, well, excitation in addition to total and partial reflection are found. From the modulational instability (MI) probed, we have found from the direct numerical simulations that long-term evolution of modulated wave exhibits chaotic behavior. Finally, energy localization through MI is conducted and a good agreement between the theoretical analysis and the numerical simulations is observed.
•Analytical and numerical study on impurity–impurity and impurity–breather interactions in a quantum 1D Klein Gordon chain.•The dynamics of the impurity mode can be significantly controlled by the impurity mass.•When the breather interacts with two impure modes, several behaviors such as trapping, chaotic trapping, well, excitation are found.•Energy localization through MI is conducted and an agreement between the theoretical analysis and the numerical simulations is observed.
Bisoprolol is a beta blocker used for the treatment of high blood pressure. During the synthesis and scale up of Bisoprolol, several related compounds will be generated. In this article we have ...disclosed a facile preparative access to the chemical synthesis of five related compounds of Bisoprolol, namely, 3,3′-((methylenebis(4,1-phenylene))bis(oxy))bis(1-(isopropylamino) propan-2-ol) (2),(Bisoprolol Ph.Eur impurity-C), 3,3′-(((oxybis(methylene))bis(4,1-phenylene)) bis(oxy))bis(1-(isopropyl amino)propan-2-ol) (3), (Bisoprolol Ph.Eur impurity-D), (±) 2-(4-((2-isopropoxyethoxy)methyl)phenoxy)-3-(isopropylamino)propan-1-ol (4), (Bisoprolol Ph.Eur impurity-F), (±) 4-((3-isopropyl-2-oxooxazolidin-5-yl)methoxy)benzaldehyde (17) (Bisoprolol Ph.Eur impurity-T), (±) 5-((4-(hydroxymethyl)phenoxy)methyl)-3-isopropyloxazolidin-2-one (18) (Bisoprolol Ph.Eur impurity-U). These related compounds were listed in Pharmacopoeias and hence these impurities were synthesized and their structure was well established by modern analytical techniques like
1
H-NMR,
13
C-NMR, HRMS. These synthetic methodologies will be useful in the future for the synthesis of other related compounds and analogues of the Bisoprolol.
Graphical abstract
Boric acid (BA) has been used as a transparent glass matrix for optical materials for over 100 years. However, recently, apparent room‐temperature phosphorescence (RTP) from BA (crystalline and ...powder states) was reported (Zheng et al., Angew. Chem. Int. Ed. 2021, 60, 9500) when irradiated at 280 nm under ambient conditions. We suspected that RTP from their BA sample was induced by an unidentified impurity. Our experimental results show that pure BA synthesized from B(OMe)3 does not luminesce in the solid state when irradiated at 250–400 nm, while commercial BA indeed (faintly) luminesces. Our theoretical calculations show that neither individual BA molecules nor aggregates would absorb light at >175 nm, and we observe no absorption of solid pure BA experimentally at >200 nm. Therefore, it is not possible for pure BA to be excited at >250 nm even in the solid state. Thus, pure BA does not display RTP, whereas trace impurities can induce RTP.
For over 100 years, boric acid (BA) has been known to serve as an excellent glass matrix for luminescent chromophores. However, in contrast to a recent report, pure BA does NOT display RTP when excited at 280 nm, and it is demonstrated experimentally that it does not absorb at λ>200 nm. Theoretical studies further reveal that pure BA cannot absorb at λ>175 nm. Thus, an impurity must be responsible for the apparent RTP in the previous report.
Edge codes such as SOLPS-ITER find distributions of impurity ions, e.g. of C, N, Ne and Ar, in the divertor and SOL which are quite non-uniform spatially, both poloidally and radially. Poloidally, ...impurity ion density distributions often have strong peaks near the targets as well as a peak on/near the separatrix in the main SOL near the outside midplane. A high density of low-Z impurities near the targets is quite desirable since cold, dense divertor plasma conditions there result in very efficient radiative dissipation of power. By contrast, impurity concentration near the outside midplane separatrix is often quite undesirable since the impurity density there is essentially the boundary value for impurity levels in the confined plasma. In order to better understand the poloidal distribution of impurities in the edge plasma, a simple analytic 1D impurity fluid model, 1DImpFM, has been developed for the transport along open field lines of impurity ions in a specified fuel-plasma background. Often, the strongest parallel forces acting on impurity ions in the edge plasma are (i) FiG, the (fuel) ion temperature parallel-gradient force ('thermal force'), and (ii) FF, the friction force between fuel and impurity ions ('friction force'). Recently, Senichenkov et al (2019 Plasma Phys. Control. Fusion 61 045013) reported the extremely useful and informative result that the impurity ion parallel velocity calculated by the SOLPS-ITER code can be remarkably well reproduced by assuming the simple force balance FF + FiG = 0. In the present paper the basis for, and a number of basic predictions of, the 1DImpFM are reported including an assessment of the circumstances under which FF + FiG = 0 can be expected to be a good approximation. The 1DImpFM is used to elucidate the competing roles of thermal and friction forces, as they control three key features of edge impurity behavior: (a) leakage of impurity ions from the divertor, (b) the peaking of impurity density near the targets, and (c) impurity ion accumulation near the midplane separatrix; the model provides simple analytic expressions for estimating the divertor leakage rate (ions/m2/s) and impurity density peaking/accumulation (ions/m3). A subsequent paper will report comparisons of results from the 1DImpFM and from SOLPS-ITER modeling of some ITER cases with neon impurities.
Three industrial case studies are presented from the pharmaceutical companies Boehringer-Ingelheim and Merck & Co., Inc. (Rahway, NJ) demonstrating how solid-state miscible impurities can ...coprecipitate during scale-up of crystallizations resulting in significant purity challenges. This second part contribution outlines how the underlying impurity retention mechanism was identified via the Solubility-Limited Impurity Purge (SLIP) test, which allowed the project teams to establish appropriate mechanism-based root-causes. The workflow and thermodynamic model introduced in part 1 of this paper series were used to guide the teams toward finding thermodynamically robust solutions for this previously unreported impurity retention mechanism. Different approaches were employed based on the prevailing solid-state miscibility, solid form landscapes, and solvent solubilities. In the first case study, an impurity present at 6% could be purged in a single crystallization by switching the crystal form. In case studies 2 and 3, solvent switches enabled the teams to reject precipitating impurities originally present at 14% and 3.5%, respectively. The presented examples showcase how mechanistic understanding of impurity retention in crystallization can be used to arrive at thermodynamically robust solutions while saving time and resources.
•Study the role of surface roughness potential (SRP) on scattering rate of double layer graphene structure (DLGS) in presence of different dielectric environment, interlayer distance and ...temperature.•Temperature dependent screening effect is incorporated using the random phase approximation (RPA) model to calculate scattering rate.•Role of low and high temperature on scattering rate in presence of surface roughness potential (SRP) and coulomb impurity (CI) of DLGS system.•Comparative study of scattering rate due to coulomb impurity (CI) and surface roughness potential (SRP) on graphene layer versus interlayer distance d (nm) of DLGS system.•The role of height & width of surface roughness (Ripples) on scattering rate by varying interlayer distance d (nm) of DLGS system.
In this work we have reported the role of surface roughness potential (SRP) on scattering rate of double layer graphene structure (DLGS) in presence of different dielectric environment, interlayer distance and temperature. We have also compared it with the scattering contribution from charged impurity (CI). In our scattering rate calculation, temperature dependent screening effect is incorporated using the random phase approximation (RPA) model. The scattering due to SRP depends on height of ripples and therefore eventually, the impurity concentration and temperature. The temperature also plays an important role in screening of the SRP. The SRP has proved to be an important factor in the low Coulomb impurity regime, while in high impurity samples SRP can be neglected. We found that above room temperature, the scattering due to SRP decreases gradually. Dielectric constant and thickness of spacer material contribute decisively to total scattering rate of DLGS.
Heavily Doped Semiconductor Nanocrystal Quantum Dots Mocatta, David; Cohen, Guy; Schattner, Jonathan ...
Science (American Association for the Advancement of Science),
04/2011, Letnik:
332, Številka:
6025
Journal Article
Recenzirano
Odprti dostop
Doping of semiconductors by impurity atoms enabled their widespread technological application in microelectronics and optoelectronics. However, doping has proven elusive for strongly confined ...colloidal semiconductor nanocrystals because of the synthetic challenge of how to introduce single impurities, as well as a lack of fundamental understanding of this heavily doped limit under strong quantum confinement. We developed a method to dope semiconductor nanocrystals with metal impurities, enabling control of the band gap and Fermi energy. A combination of optical measurements, scanning tunneling spectroscopy, and theory revealed the emergence of a confined impurity band and band-tailing. Our method yields n- and p-doped semiconductor nanocrystals, which have potential applications in solar cells, thin-film transistors, and optoelectronic devices.
•The addition of N2 to CO2 is effective for recovery of CH4 in gas hydrate.•The penetration capability of the replacement phase is sensitive to the ratio of N2 to CO2.•The function of N2 is not only ...replacement but also decomposition of CH4 hydrate.
Replacement of methane (CH4) in CH4 hydrate by carbon dioxide (CO2) can enable recovery of CH4, which is a potential future energy resource, while sequestering CO2 to mitigate the effects of global warming. However, little work has been done to address the effects of impurities on CO2 replacement, and the detailed mechanisms. Here, microsecond molecular dynamics simulations were performed to understand the influence of nitrogen (N2) gas on the process of replacing CH4 in CH4 hydrate with CO2 at 280 K and 6 MPa. The results show that CO2 molecules can penetrate more deeply into CH4 hydrate phase when it is mixed with N2. This is mainly because N2 can favor the decomposition of CH4 hydrate and expand the replacement area of CH4 by guest molecules. We confirm that the replacement of CH4 by CO2 and N2 preferably occurs in large and small cages, respectively. In most cases, a mixture hydrate reforms at the outmost layer of the hydrate surface. The CO2/N2 mixture shows an overall higher replacement efficiency than pure CO2 case. Our work demonstrates that CH4 recovery by CO2 injection in CH4 hydrate can be facilitated by N2. The penetration depth of replacement is sensitive to the ratio of N2 to CO2. The knowledge obtained in this study will be helpful for the effective utilization of CO2/N2 mixtures to maximize the recovery percentage of CH4 from hydrate.
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