Light-absorbing impurities on Keqikaer Glacier in western Tien Shan: concentrations and potential impact on albedo reduction

Light-absorbing impurities on glaciers are important factors that influence glacial surface albedo and accelerate glacier melt. In this study, the quantity of light-absorbing impurities on Keqikaer Glacier in western Tien Shan, Central Asia, was measured. We found that the average concentrations of black carbon was 2,180 ng/g, with a range from 250 ng/g to more than 10,000 ng/g. The average concentrations of organic carbon and mineral dust were 1,738 ng/g and 194 μg/g, respectively. Based on simulations performed with the Snow Ice Aerosol Radiative model simulations, black carbon and dust are responsible for approximately 64% and 9%, respectively, of the albedo reduction, and are associated with instantaneous radiative forcing of 323.18 W/m2(ranging from 142.16 to 619.25 W/m2) and 24.05 W/m2(ranging from 0.15 to69.77 W/m2), respectively. For different scenarios, the albedo and radiative forcing effect of black carbon is considerably greater than that of dust. The estimated radiative forcing at Keqikaer Glacier is higher than most similar values estimated by previous studies on the Tibetan Plateau, perhaps as a result of black carbon enrichment by melt scavenging. Light-absorbing impurities deposited on Keqikaer Glacier appear to mainly originate from central Asia, Siberia, western China(including the Taklimakan Desert) and parts of South Asia in summer, and from the Middle East and Central Asia in winter.A footprint analysis indicates that a large fraction(>60%) of the black carbon contributions on Keqikaer Glacier comes from anthropogenic sources. These results provide a scientific basis for regional mitigation efforts to reduce black carbon.

Quantification of Structurally Alert Mutagenic Impurities in Meropenem Trihydrate Drug Substance by Liquid Chromatography with High Resolution Mass Spectrometer (LC-HRMS)

Potential mutagenic impurities in Active Pharmaceutical Ingredient, Meropenem Trihydrate were assessed and a novel analytical method for their quantification was developed and validated. This Liquid Chromatographic method using High Resolution Mass Spectrometer (LC-HRMS) technique is proved to be suitable for simultaneous quantification of all ten identified impurities with required specificity, sensitivity, resolution, precision, accuracy, and other method characteristics as per ICH Guidelines. The acceptable limit of less than 2.9 μg/g was considered for evaluations, based on drug substance dosage and duration of treatment. The method stands most sensitive with a Limit of Detection of 0.35 μg/g, considering the challenge full acceptance criteria as per current regulatory standards.

Solriamfetol impurities:Synthesis,characterization,and analytical method(UPLC-UV)validation

Given that impurities may affect the quality and safety of drug products,impurity identification and profiling is an integral part of drug quality control and is particularly important for newly developed medications such as solriamfetol,which is used to treat excessive daytime sleepiness.Although the highperformance liquid chromatography analysis of commercial solriamfetol has revealed the presence of several impurities,their synthesis,structure elucidation,and chromatographic determination have not been reported yet.To bridge this gap,we herein identified,synthesized,and isolated eight processrelated solriamfetol impurities,characterized them using spectroscopic and chromatographic techniques,and proposed plausible mechanisms of their formation.Moreover,we developed and validated a prompt impurity analysis method based on ultrahigh-performance liquid chromatography with UV detection,revealing that its selectivity,linearity,accuracy,precision,and quantitation limit meet the acceptance criteria of method validation stipulated by the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use.Thus,the developed method was concluded to be suitable for the routine analysis of solriamfetol substances.

Prediction of impurity spectrum function by deep learning algorithm

By using the numerical renormalization group(NRG)method,we construct a large dataset with about one million spectral functions of the Anderson quantum impurity model.The dataset contains the density of states(DOS)of the host material,the strength of Coulomb interaction between on-site electrons(U),and the hybridization between the host material and the impurity site(Γ).The continued DOS and spectral functions are stored with Chebyshev coefficients and wavelet functions,respectively.From this dataset,we build seven different machine learning networks to predict the spectral function from the input data,DOS,U,andΓ.Three different evaluation indexes,mean absolute error(MAE),relative error(RE)and root mean square error(RMSE),are used to analyze the prediction abilities of different network models.Detailed analysis shows that,for the two kinds of widely used recurrent neural networks(RNNs),gate recurrent unit(GRU)has better performance than the long short term memory(LSTM)network.A combination of bidirectional GRU(BiGRU)and GRU has the best performance among GRU,BiGRU,LSTM,and BiLSTM.The MAE peak of BiGRU+GRU reaches 0.00037.We have also tested a one-dimensional convolutional neural network(1DCNN)with 20 hidden layers and a residual neural network(ResNet),we find that the 1DCNN has almost the same performance of the BiGRU+GRU network for the original dataset,while the robustness testing seems to be a little weak than BiGRU+GRU when we test all these models on two other independent datasets.The ResNet has the worst performance among all the seven network models.The datasets presented in this paper,including the large data set of the spectral function of Anderson quantum impurity model,are openly available at https://doi.org/10.57760/sciencedb.j00113.00192.

Gyro-Landau-fluid simulations of impurity effects on ion temperature gradient driven turbulence transport

The effects of impurities on ion temperature gradient(ITG)driven turbulence transport in tokamak core plasmas are investigated numerically via global simulations of microturbulence with carbon impurities and adiabatic electrons.The simulations use an extended fluid code(ExFC)based on a four-field gyro-Landau-fluid(GLF)model.The multispecies form of the normalized GLF equations is presented,which guarantees the self-consistent evolution of both bulk ions and impurities.With parametric profiles of the cyclone base case,well-benchmarked ExFC is employed to perform simulations focusing on different impurity density profiles.For a fixed temperature profile,it is found that the turbulent heat diffusivity of bulk ions in a quasi-steady state is usually lower than that without impurities,which is contrary to the linear and quasilinear predictions.The evolutions of the temperature gradient and heat diffusivity exhibit a fast relaxation process,indicating that the destabilization of the outwardly peaked impurity profile is a transient state response.Furthermore,the impurity effects from different profiles can obviously influence the nonlinear critical temperature gradient,which is likely to be dominated by linear effects.These results suggest that the improvement in plasma confinement could be attributed to the impurities,most likely through adjusting both heat diffusivity and the critical temperature gradient.

EFFECT OF INTERSTITIAL IMPURITIES ON THE PHASETRANSFORMATION OF Ti-Al ALLOYS

应用固体与分子经验电子理论的平均晶胞和平均原子模型分析计算了间隙杂质对Ti-Al合金价电子结构和相变的影响。同时根据该理论的键能公式计算了间隙杂质影响下的键能、熔点和液相线的变化。据此解释了Ti-Al合金相变目前尚有争议的主要实验结果。表明，间隙杂质提高了合金元素的原子杂阶，引起键结构呈严重的各向异性，阻碍了β→α相转变，导致中间成分相变的复杂性。间隙杂质也降低了熔点及高温液相线，采用近似处理由该理论可较好地计算其平均降低程度。

Role of trivalent antimony in the removal of As, Sb, and Bi impurities from copper electrolytes

The role of trivalent antimony was investigated in removing As, Sb, and Bi impurities from a copper electrolyte. Puri- fication experiments were carried out by adding a various concentrations of Sb（III） ions in a synthetic electrolyte containing 185 g/L sulfuric acid, 45 g/L Cu2＋, 10 g/L As, and 0.5 g/L Bi under stirring at 65℃ for 2 h. The electrolyte was filtered, and the structure, morphology and composition of the precipitate were analyzed by means of chemical analysis, scanning electron mi- croscopy （SEM）, X-ray diffraction （XRD）, transmission electron microscopy （TEM）, and IR spectroscopy. The precipitate is composed of irregular lumps which are agglomerated by fine dendritic and floccus particles, and it mainly consists of As, Sb, Bi, and O elements. Characteristic bands in the IR spectra of the precipitate are As-OX （X=As, Sb, Bi）, Sb-OY （Y=Sb, Bi）, O-As-O1 As-OH, Sb-OH, and O-H. The precipitate is a mixture of microcrystalline SbAsQ, （Sb,As）203, and amorphous phases. As, Sb, and Bi impurities are effectively removed from the copper electrolyte by Sb（III） ions attributing to these pre- cipitates.

Impurities evaporation from metallurgical-grade silicon in electron beam melting process

The purification of metallurgical-grade silicon （MG-Si） has been investigated during electron beam melting （EBM） process. The results show that the phosphorus, calcium and aluminum contents decrease significantly after melting, and magnesium is partially removed. However, no significant change in content for boron and iron has been found. Langmuir＇s equation and Henry law were used to derive the removal effi-ciency for each impurity element. The free surface temperature was estimated by the Hertz-Knudsen-Langmuir equation and silicon＇s vapor pressure equation. Good agreement was found between measured and calculated impurities＇ removal efficiency for phosphorus, calcium and aluminum, magnesium, boron and iron. The deviation between the two results was also analyzed in depth.

Electronic Theoretical Study of the Interaction between Rare Earth Elements and Impurities at Grain Boundaries in Steel

The model of dislocations was used to construct the model of grain boundary (GB) with pure rare earths, and rare earth elements and impurities. The influence of the interaction between rare earth elements and impurities on the cohesive properties of 5.3° low angle GB of Fe was investigated by the recursion method. The calculated results of environment sensitive embeding energy( E ESE ) show that the preferential segregation of rare earth elements towards GBs exists. Calculations of bond order integrals (BOI) show that rare earth elements increase the cohesive strength of low angle GB, and impurities such as S, P weaken the intergranular cohesion of the GB. So rare earth element of proper quantity added in steel not only cleanses other harmful impurities off the GBs, but also enhances the intergranular cohesion. This elucidates the action mechanism of rare earth elements in steel from electronic level and offers theoretical evidence for applications of rare earth elements in steels.

Influence of nitrogen impurities on the characteristics of a patterned helium dielectric barrier discharge at atmospheric pressure

In this paper, a two-dimensional axisymmetric fluid model was established to investigate the influence of nitrogen impurity content on the discharge pattern and the relevant discharge characteristics in an atmosphere pressure helium dielectric barrier discharge(DBD). The results indicated that when the nitrogen content was increased from 1 to 100 ppm, the discharge pattern evolved from a concentric-ring pattern into a uniform pattern, and then returned to the concentricring pattern. In this process, the discharge mode at the current peak moment transformed from glow mode into Townsend mode, and then returned to glow mode. Further analyses revealed that with the increase of impurity level, the rate of Penning ionization at the pre-ionization stage increased at first and decreased afterwards, resulting in a similar evolution pattern of seed electron level. This evolution trend was believed to be resulted from the competition between the N2 partial pressure and the consumption rate of metastable species. Moreover, the discharge uniformity was found positively correlated with the spatial uniformity of seed electron density as well as the seed electron level. The reason for this correlation was explained by the reduction of radial electric field strength and the promotion of seed electron uniformity as pre-ionization level increases. The results obtained in this work may help better understand the pattern formation mechanism of atmospheric helium DBD under the variation of N2 impurity level, thereby providing a possible means of regulating the discharge performance in practical application scenarios.

Quantification of trace amounts of impurities in high purity cobalt by high resolution inductively coupled plasma mass spectrometry

A An analytical method using high resolution inductively coupled plasma mass spectrometry （HR-ICP-MS） for rapid simultaneous determination of 24 elements （Be, Mg, A1, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga, Ge, As, Se, Mo, Ag, Cd, Sn Sb, Ba, Pt, Au, and Pb） in high purity cobalt was described. Sample digestions were performed in closed microwave vessels using HNO3 and HCI. The matrix effects because of the presence of excess HCI and Co were evaluated. The usefulness of high mass resolution for overcoming some spectral interference was demonstrated. The optimum conditions for the determination were tested and discussed. The standard addition method was employed for quantitative analysis. The detection limits were 0.016-1.50 ].tg·g^-1, the recovery ratios were 92.2%-111.2%, and the RSD was less than 3.6%. The method was accurate, quick, and convenient. It was applied to the determination of trace impurities in high purity cobalt with satisfactory results.

The impacts of gas impurities on the minimum miscibility pressure of injected CO_2-rich gas–crude oil systems and enhanced oil recovery potential

An effective parameter in the miscible-CO_2 enhanced oil recovery procedure is the minimum miscibility pressure(MMP)defined as the lowest pressure that the oil in place and the injected gas into reservoir achieve miscibility at a given temperature. Flue gases released from power plants can provide an available source of CO_2,which would otherwise be emitted to the atmosphere, for injection into a reservoir. However, the costs related to gas extraction from flue gases is potentially high. Hence, greater understanding the role of impurities in miscibility characteristics between CO_2 and reservoir fluids helps to establish which impurities are tolerable and which are not. In this study, we simulate the effects of the impurities nitrogen(N_2), methane(C_1), ethane(C_2) and propane(C_3) on CO_2 MMP. The simulation results reveal that,as an impurity, nitrogen increases CO_2–oil MMP more so than methane. On the other hand, increasing the propane(C_3)content can lead to a significant decrease in CO_2 MMP, whereas varying the concentrations of ethane(C_2) does not have a significant effect on the minimum miscibility pressure of reservoir crude oil and CO_2 gas. The novel relationships established are particularly valuable in circumstances where MMP experimental data are not available.

Solid-state characterization and impurities determination of fluconazol generic products marketed in Morocco

In this paper, we report the results of quality control based in pbysicochemical characteriza- tion and impurities determination of three samples of fluconazole drug substances marketed in Morocco. These samples were supplied by different pharmaceuticals companies. The sample A, as the discovered product, was supplied by Pfizer, while samples B and C （generics）, were manufactured by two different Indian industries. Solid-state characterization of the three samples was realized with different physicochemical methods as： X-ray powder diffraction, Fourier-transformation infrared spectroscopy, differential scanning calorimetry. High performance liquid chromatography was used to quantify the impurities in the different samples. The results from the physicochemical methods cited above, showed difference in polymorph structure of the three drug substances. Sample A consisted in pure polymorph II1, sample B consisted in pure polymorph I1, sample C consisted in a mixture of fluconazole Form Ili, form II and the monohydrate. This result was confirmed by differential scanning calorimetry. Also it was demonstrated that solvents used during the re-crystallization step were among the origins of these differences in the structure form. On the other hand, the result of the stability study under humidity and temperature showed that fluconazole polymorphic transformation could be owed to the no compliance with the conditions of storage. The HPLC analysis of these compounds showed the presence of specific

A review of electrolyte additives and impurities in vanadium redox flow batteries

As one of the most important components of the vanadium redox flow battery （VRFB）, the electrolyte can impose a significant impact on cell properties, performance and capital cost. In particular, the electrolyte composition will influence energy density, operating temperature range and the practical applications of the VRFB. Various approaches to increase the energy density and operating temperature range have been proposed. The presence of electrolyte impurities, or the addition of a small amount of other chemical species into the vanadium solution can alter the stability of the electrolyte and influence cell perfor- mance, operating temperature range, energy density, electrochemical kinetics and cost effectiveness. This review provides a detailed overview of research on electrolyte additives including stabilizing agents, im- mobilizing agents, kinetic enhancers, as well as electrolyte impurities and chemical reductants that can be used for different purposes in the VRFBs.

A developed HPLC method for the determination of Alogliptin Benzoate and its potential impurities in bulk drug and tablets

Alogliptin(AGLT),active ingredient of Alogliptin Benzoate(AGLT-BZ),is a new dipeptidyl peptidase-4(DPP-4)inhibitor for the treatment of type 2 diabetes.This study aimed to build a suitable method to determine the potential related substances in AGLT-BZ bulk drug and tablets.Seven related substances in Alogliptin Benzoate substances were synthetized and identified by ^(1)H-NMR and ESI-MS.In addition,the impurities were detected by a gradient reverse-phase high performance liquid chromatography(RP-HPLC)with UV detection.The chromatographic system consisted of an Angilent Zobax SB-CN column(250×4.6 mm;5 μm).The mobile phase consisted of water/acetonitrile/trifluoroacetic acid 1900:100:1 v/v/v(solution A)and acetonitrile/water/trifluoroacetic acid 1900:100:1 v/v/v(solution B)using a gradient program at a flow rate of 1.0 ml/min with 278 nm detection and an injection volume of 20 ml.Additionally,selectivity,the limit of quantitation(LOQ)and limit of detection(LOD),linearity,accuracy,precision and robustness were determined.Linearity was good over the concentration range 50-1000 ng/ml and the coefficient of determination(R^(2))were 0.9991-0.9998.RSD% of the determination of precision were <2%(n=6).The method of RP-HPLC for the determination of impurities in AGLT-BZ was proved to be precise,accurate,robust and reliable.Three batches of self-made bulk drug and three dosages of commercial tablets were detected with this method.

Effect of Impurities and Ce on the Anisotropic Behavior of 8090 Alloy Sheet

The tests were carried out to investigate the effect of the impurities and rare earth element on the anisotropic behavior of 8090 alloy sheet. The results show that the impurites such as Fe and Si reduce the ductility, fracture toughness in all orientations, and reduce the strength in transverse orientation, but enhance the strength in 45 degrees orientation. The strength, ductility and fracture toughness are greatly reduced when the alloy has a higher concentration of alkali metal impurities, and even the anisotropy may be weakened by the impurities. An improvement over the ductility, fracture toughness and anisotropic behavior except the strength for the alloy sheet containing more Fe and Si impurities can be made by adding 0.28% Ce element. As a result, its ductility and fracture toughness have been above those of the high-purity alloy sheet.

Quantification of Trace Amounts of Impurities in High Purity Cobalt by High Resolution Inductively Coupled Plasma Mass Spectrometry

An analytical method using high resolution inductively coupled plasma mass spectrometry （HR-ICP-MS） for rapid simultaneous determination of Be, Mg, Al, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga, Ge, As, Se, Mo, Ag, Cd, Sn, Sb, Ba, Pt, Au and Pb in high purity cobalt was described. Sample digestions were performed in closed microwave vessels using HNO3 and HCl. The matrix effects due to the presence of excess HCl and Co were evaluated. The usefulness of high mass resolution for overcoming some spectral interference was demonstrated. The optimum conditions for the determination was tested and discussed. Correction for matrix effects, Sc, Rh and Bi were used as internal standards. The detection limits is 0.003-0.57 μg/g, the recovery ratio is 92.2%-111.2%, and the RSD is less than 3.6%. The method is accurate, quick and convenient. It has been applied to the determination of trace impurities in high purity cobalt with satisfactory results.

Risk evaluation of impurities in topical excipients:The acetol case

Pharmaceutical excipients for topical use may contain impurities, which are often neglected from a toxicity qualification viewpoint. The possible impurities in the most frequently used topical excipients were evaluated in-silico for their toxicity hazard. Acetol, an impurity likely present in different topical pharmaceutical excipients such as propylene glycol and glycerol, was withheld for the evaluation of its health risk after dermal exposure. 〈br〉 An ex-vivo in-vitro permeation study using human skin in a Franz Diffusion Cell set-up and GC as quantification methodology showed a significant skin penetration with an overall Kp value of 1.82 ？ 10 ？ 3 cm/h. Using these data, limit specifications after application of a dermal pharmaceutical product were estimated. Based on the TTC approach of Cramer class I substances, i.e. 1800 mg/（day？person）, the toxicity-qualified specification limits of acetol in topical excipients were calculated to be 90 mg/mL and 180 mg/mL for propylene glycol and glycerol, respectively.

Disruption mitigation using laser ablation of high-Z impurities in HL-1M tokamak

A preliminary experiment triggering a plasma current quench by laser ablation of high-Z impurities has been performed in the HL-1M tokamak. The injection of impurities with higher electric charges into tokamak plasmas can increase the radiation cooling of the plasma. Resistive, highly radiating plasma formed prior to the thermal quench can dissipate both the thermal and magnetic energies, which is possibly a simple and potential approach to reducing significantly the plasma thermal energy and magnetic energy before a disruption thereby a safe plasma termination is obtained.

Direct Determination of Trace Impurities in High Purity Zinc Oxide by High Resolution Inductively Coupled Plasma Mass Spectrometry

The determination of trace impurities in high purity zinc oxide by high resolution inductively coupled plasma mass spectrometry （ HR-ICP-MS ） was investigated. To overcome some poteutially problematic spectral iuterference, measurements were acquired in both middle and high resolution modes. The matrix effects due to the presence of excess HCl and zinc were evaluated. The optimum conditions for the determination were tested and discussed. The standard addition method was employed for quantitative analysis. The detection limits ranged from 0.02μg/ g to 6 μg/ g depending on the elements. The experimental resalts for the determination of Na, Mg, Ca, Cr, Mn, Fe, Co, Ni, Cu, Mo, Cd, Sb and Pb in several high purity zinc oxide powders were presented.