Vapor phase treatment (VPT) was under investigation by the International Organization for Standardization/Technical Committee 201/Working Group 2 (ISO/TC201/WG2) to improve the detection limit of ...total reflection X-ray fluorescence spectroscopy (TXRF) for trace metal analysis of silicon wafers. Round robin test results have confirmed that TXRF intensity increased by VPT for intentional contamination with 5×109 and 5×1010atoms/cm2 Fe and Ni. The magnification of intensity enhancement varied greatly (1.2–4.7 in VPT factor) among the participating laboratories, though reproducible results could be obtained for average of mapping measurement. SEM observation results showed that various features, sizes, and surface densities of particles formed on the wafer after VPT. The particle morphology seems to have some impact on the VPT efficiency. High resolution SEM observation revealed that a certain number of dots with SiO2, silicate and/or carbon gathered to form a particle and heavy metals, Ni and Fe in this study were segregated on it. The amount and shape of the residue should be important to control VPT factor.
•This paper presents a summary of study results of VPT–TXRF using ISO/TC201/WG2.•Our goal is to analyze the trace metallic contamination on silicon wafer with concentrations below 1×1010 atoms/cm2.•The efficiency and mechanism of VPT are discussed under several round robin tests and systematic studies.
We report on instrumentation-related challenges of applying graphite furnace atomic absorption spectroscopy (GF-AAS) and inductively coupled plasma mass spectrometry (ICP-MS). We show that a ...significant amount of polyatomic species derived from silicon sample solution in the plasma, such as SiO, SiOH, SiOH
2·SiOH
3, SiO
2, SiO
2H, SiO
2H
2 and SiO
2H
3, can hamper the detection limits of many elements of interest. This paper describes a method for eliminating these polyatomic ions. We discuss the advantages and disadvantages of vapor phase decomposition method (VPD), drop etching method (DE) and drop sandwich-etching method (DSE) for the recovery of metal impurities from a silicon wafer surface. We report the application of the DSE method for the evaluation of near-surface metal impurities, used for gettering studies. We describe the direct acid bulk decomposition (DABD) and the room temperature acid vapor phase decomposition method (RT-AVPD) for the determination of metal impurities in bulk silicon. Finally, we report concentration of trace metal contamination in several chemical reagent solutions.
A method for the analysis of sub parts per trillion levels of rare-earth elements (REEs) and yttrium (Y) in seawater after preconcentration with solvent extraction and back-extraction has been ...developed. Almost perfect extraction and back-extraction of all REE and Y were achieved by single extraction, and most of the matrix elements were removed during the extraction procedure. Even after 200-fold preconcentration, matrix problems by ICP-MS measurement were negligible. Contamination from reagents and water used during the pretreatment was below 1% of the concentration of REE and Y in seawater. The standard deviation obtained for triplicate separation of 100- and 1,000-mL samples of the same seawater was better than 5% for all REE. The average precision of the measurement for all REE and Y after preconcentration of 1,000 mL of raw seawater to 5 mL of final measurement solution was calculated to be less than 2.5%. Since there is no standard seawater sample for REE and Y, in order to evaluate this novel technique, the analytical results obtained by this method were compared with those obtained by isotope dilution mass spectrometry coupled with Fe coprecipitation.
A method has been developed for the determination of the rare earth elements (REE) at concentrations down to 0.1 ppt (0.5 pmol kg-1) in aqueous samples using flow injection coupled to an inductively ...coupled plasma mass spectrometer. The method presented here is an extension of an existing technique to allow application to a wider range of ionic strengths. The method is sufficiently rapid to enable samples to be processed through the purification stage in less than 90 min. More than 99.5% of the Ba in the sample is removed during processing, ensuring that isobaric interference of BaO on the REE is <2% of the REE signal. The detection limits of the method described here show an improvement of up to 30 times better than the original method. This improvement was achieved by using flow injection techniques that allow the sample to be concentrated in a smaller volume for analysis. The new technique has been successfully employed for the determination of REE in Icelandic hydrothermal fluids.
In the present research, a novel process was proposed and assessed using an equilibrium thermochemical modelling study to evaluate the performance of a combined disruptive technology of thermal ...plasma and thermochemical looping to utilise hydrogen for iron reduction processing. The study was aimed at conducting a high-level power performance assessment of the process by integrating a built-in power block with a focus on a novel equilibrium thermal plasma technology for reducing iron scrap particles. The effect of thermal plasma operating parameters such as temperature (1000 °C < T < 1800 °C) and hydrogen-to-iron ratio in the feed stream to the thermal plasma reactor (0 < H2/metal < 20) on the performance of the system was numerically investigated using Aspen coupled with Matlab. Also, the self-sustaining factor was evaluated coupled with a quantitative analysis of the sustainability and lifecycle of the process aiming at better understanding the impact of the proposed system on the environment. Results showed that the system is crucially sensitive to the ratio of H2/metal such that the overall power demand of the reactor can change in a way that the dominant regime of the plasma can change from endothermic (partial reduction of iron) to exothermic (complete reduction, combustion of iron) once the hydrogen to metal ratio exceeds ∼ 2.5. It was also identified that an increase in the temperature of the combustor decreased the power demand for the thermal plasma reactor. Similarly, with increasing the temperature, a ramp-up in the self-sustaining factor was observed reaching 0.8 showing that 80 % of the energy of the auxiliaries can be maintained using the built-in heat recovery and power block. The thermal efficiency of the system was also a strong function of the H2/metal ratio reaching ∼ 0.4 at the H2/metal ratio of ∼ 2.5 reflecting the fact that the proposed process efficiency is within the state-of-the-art power production systems. The sustainability assessments showed that the process offers a high circular economy capability of the process with above-the-average lifetime and Material Circularity Indicator values.
Over-expression of K+ channels has been reported in human cancers and is associated with the poor prognosis of several malignancies. EAG1, a particular potassium ion channel, is widely expressed in ...the brain but poorly expressed in other normal tissues. Kunitz proteins are dominant in metazoan including the dog tapeworm, Echinococcus granulosus. Using computational analyses on one A-type potassium channel, EAG1, and in vitro cellular methods, including major cancer cell biomarkers expression, immunocytochemistry and whole-cell patch clamp, we demonstrated the anti-tumor activity of three synthetic small peptides derived from E. granulosus Kunitz4 protease inhibitors. Experiments showed induced significant apoptosis and inhibition of proliferation in both cancer cell lines via disruption in cell-cycle transition from the G0/G1 to S phase. Western blotting showed that the levels of cell cycle-related proteins including P27 and P53 were altered upon kunitz4-a and kunitz4-c treatment. Patch clamp analysis demonstrated a significant increase in spontaneous firing frequency in Purkinje neurons, and exposure to kunitz4-c was associated with an increase in the number of rebound action potentials after hyperpolarized current. This noteworthy component in nature could act as an ion channel blocker and is a potential candidate for cancer chemotherapy based on potassium channel blockage.
In cancer treatments, smart gene delivery via nanoparticles (NPs) can be targeted for cancer cells, while concurrently minimizing damage to healthy cells. This study assessed the efficiency of poly ...lactic-co-glycolic acid (PLGA)-miR 143/206 transfection on apoptosis in mouse leukemia cancer cells (El4) and spermatogonial stem cells (SSCs).
In this experimental study, neonatal mouse spermatogonia cells and EL4 cancer cell lines were used. MicroRNA-PLGA NPs were prepared, characterized, and targeted with folate. Several doses were evaluated to obtain a suitable miR dose that can induce appropriate apoptosis in EL4 cells, while not harming SSCs. Cells were treated separately at 3 doses of each miR (for miR 143, doses of 25, 50 and 75 nmol and for miR 206, doses of 50, 100 and 150 nmol). The experiments were performed at 24, 48 and 72 hours. Viability and apoptosis were investigated by MTT and Annexin Kits.
Based on MTT assay results, the optimal dose of miR 143 was 75 nmol (59.87 ± 2.85 % SSC and 35.3 ± 0.78 % EL4) (P≤0.05), and for miR 206, the optimal dose was 150 nmol (54.82 ± 6.7 % SSC and 33.92 ± 3.01% EL4) (P≤0.05). The optimal time was 48 hours. At these doses, the survival rate of the EL4 cells was below the half maximal inhibitory concentration (IC
) and SSC survival was above 50%. Annexin V staining also confirmed the selected doses (for miR 143 total apoptosis was 6.62% ± 1.8 SSC and 37.4% ± 4.2 EL4 (P≤0.05), and miR 206 was (10.98% ± 1.5 SSC and 36.4% ± 3.7 EL4, P≤0.05).
Using intelligent transfection by NPs, we were able to induce apoptosis on EL4 cells and maintain acceptable SSC survival rates.
Four parabolic functions were derived separately for the first, the second, the third and the fourth tetrads of lanthanides in samples of leuco-granitic gneiss from Korea, and seawater from off the ...coasts of Shimane and Kochi prefectures, Japan. We conclude that relative lanthanide abundances in each of those samples are mathematically expressed by a set of four parabolic functions. The parabolic functions are applicable to the abundance ratio values as well as the values of aberration from the cusp-spanning lines. Both parabolic function systems are significant in different senses, but a set of four parabolas for “aberration” is convenient in visualizing the characteristics of lanthanide tetrad phenomenon observed for the sample. Difference in those characteristics can be interpreted to reflect uniquely the state of lanthanides present and/or the condition of genesis of the sample.
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