Static Ion Research Articles

ZEST: A Fast Code for Simulating Zeeman-Stark Line-Shape Functions

We present the ZEST code, dedicated to the calculation of line shapes broadened by Zeeman and Stark effects. As concerns the Stark effect, the model is based on the Standard Lineshape Theory in which ions are treated in the quasi-static approximation, whereas the effects of electrons are represented by weak collisions in the framework of a binary collision relaxation theory. A static magnetic field may be taken into account in the radiator Hamiltonian in the dipole approximation, which leads to additional Zeeman splitting patterns. Ion dynamics effects are implemented using the fast Frequency-Fluctuation Model. For fast calculations, the static ion microfield distribution in the plasma is evaluated using analytic fits of Monte-Carlo simulations, which depend only on the ion-ion coupling parameter and the electron-ion screening factor.

Ion Exchange Resin on Treatment of Copper and Nickel Wastewater

On the conditions of static and dynamic ion exchange, the removal effect of Cu2+ and Ni2+ by D001 resin was investigated. Besides, the thermodynamic and kinetic characteristics in the process of adsorption were studied. The results showed that when the initial concentrations of Cu2+ and Ni2+ in the copper and nickel wastewater were 100mg/L, the temperature was 25°C and pH was 5, the removal rate at the state of equilibrium were 99.14% and 99.33% respectively. In the dynamic ion exchange experiment, when the influent flow rate was 10L/h, the exchange capacity of the resin was 13829.79mg/L for Cu2+ and 22656.70mg/L for Ni2+ at the time of breakthrough.

Quantitative Collision Cross-Sections from FTICR Linewidth Measurements: Improvements in Theory and Experiment.

Two corrections to the equation used in the cross-sectional areas by Fourier transform ion cyclotron resonance ("CRAFTI") technique are identified. In CRAFTI, ion collision cross-sections are obtained from the pressure-dependent ion linewidths in Fourier transform mass spectra. The effects of these corrections on the accuracy of the cross-sections obtained using the CRAFTI technique are evaluated experimentally using the 20 biogenic amino acids and several crown ether complexes with protonated alkyl monoamines. Good absolute agreement is obtained between the CRAFTI cross-sections and the corresponding cross-sections obtained using both static drift ion mobility spectrometry and computational simulations. These results indicate that the CRAFTI cross-sections obtained using the updated equation presented here are quantitatively descriptive of the size and shape of the gas-phase ions. Cross-sections that differ by less than 3% are measured for the isobaric isomers n-butylamine and tert-butylamine complexed with the crown ethers. This level of precision is similar to what has been achieved previously using traveling wave ion mobility devices. These results indicate that CRAFTI can be used to probe subtle structural differences between ions with approximately the same precision as that achieved in traveling wave ion mobility devices. Graphical Abstract ᅟ.

Research and development regarding the retaining mechanism of lead ions in industrial wastewaters using natural matter with remarkable properties

The paper shows the studying of the retaining mechanism of lead ions in industrial wastewaters through static and dynamic ion exchange mechanisms. In the experimental determinations of the lead metallic ion retention, metallurgical industry wastewaters have been used on samples of volcanic zeolite tuff (from Barsana, Maramures), samples that show a high concentration of lead ions and an acidic pH. The results showed that both the static and the dynamic ion exchanges ended with good results and they were consistent with other studies conducted on clinoptilolite zeolite tuff. Knowing that the industrial sector is an important source of environment pollution and degradation and being aware of what a serious threat the heavy metal pollution is, due to their high toxicity and stability, the experiment may find applicability in different aspects, both in the Maramures mining basing as well as in the worldwide controlling and directing of the polluting processes.

Collisional Cross-Sections with T-Wave Ion Mobility Spectrometry without Experimental Calibration.

A method for relating traveling-wave ion mobility spectrometry (TWIMS) drift times with collisional cross-sections using computational simulations is presented. This method is developed using SIMION modeling of the TWIMS potential wave and equations that describe the velocity of ions in gases induced by electric fields. The accuracy of this method is assessed by comparing the collisional cross-sections of 70 different reference ions obtained using this method with those obtained from static drift tube ion mobility measurements. The cross-sections obtained here with low wave velocities are very similar to those obtained using static drift (average difference = 0.3%) for ions formed from both denaturing and buffered aqueous solutions. In contrast, the cross-sections obtained with high wave velocities are significantly greater, especially for ions formed from buffered aqueous solutions. These higher cross-sections at high wave velocities may result from high-order factors not accounted for in the model presented here or from the protein ions unfolding during TWIMS. Results from this study demonstrate that collisional cross-sections can be obtained from single TWIMS drift time measurements, but that low wave velocities and gentle instrument conditions should be used in order to minimize any uncertainties resulting from high-order effects not accounted for in the present model and from any protein unfolding that might occur. Thus, the method presented here eliminates the need to calibrate TWIMS drift times with collisional cross-sections measured using other ion mobility devices. Graphical Abstract ᅟ.

A chromatographic approach to distinguish Gram-positive from Gram-negative bacteria using exogenous volatile organic compound metabolites

This paper utilized L-alanine aminopeptidase activity as a useful approach to distinguish between Gram-negative and Gram-positive bacteria. This was done using two enzyme substrates, specifically 2-amino-N-phenylpropanamide and 2-amino-N-(4-methylphenyl)propanamide which liberated the volatile compounds aniline and p-toluidine, respectively. Two complementary analytical techniques have been used to identify and quantify the VOCs, specifically static headspace multicapillary column gas chromatography ion mobility spectrometry (SHS-MCC-GC-IMS) and headspace solid phase microextraction gas chromatography mass spectrometry (HS-SPME-GC–MS). Superior limits of detection were obtained using HS-SPME-GC–MS, typically by a factor of x6 such that the LOD for aniline was 0.02μg/mL and 0.01μg/mL for p-toluidine. In addition, it was also possible to determine indole interference-free by HS-SPME-GC–MS at an LOD of 0.01μg/mL. The approach was applied to a range of selected bacteria: 15 Gram-negative and 7 Gram-positive bacteria. Use of pattern recognition, in the form of Principal Component Analysis, confirmed that it is possible to differentiate between Gram-positive and Gram-negative bacteria using the enzyme generated VOCs, aniline and p-toluidine. The exception was Stenotrophomonas maltophilia which showed negligible VOC concentrations for both aniline and p-toluidine, irrespective of the analytical techniques used and hence was not characteristic of the other Gram-negative bacteria investigated. The developed methodology has the potential to be applied for clinical and food applications.

Total fluid pressure imbalance in the scrape-off layer of tokamak plasmas

Simulations using the fully kinetic neoclassical code XGCa (X-point included guiding- center axisymmetric) were undertaken to explore the impact of kinetic effects on scrape-off layer (SOL) physics in DIII-D H-mode plasmas. XGCa is a total-f, gyrokinetic code which self-consistently calculates the axisymmetric electrostatic potential and plasma dynamics, and includes modules for Monte Carlo neutral transport.Previously presented XGCa results showed several noteworthy features, including large variations of ion density and pressure along field lines in the SOL, experimentally relevant levels of SOL parallel ion flow (Mach number ∼ 0.5), skewed ion distributions near the sheath entrance leading to subsonic flow there, and elevated sheath potentials (Churchill 2016 Nucl. Mater. Energy 1–6).In this paper, we explore in detail the question of pressure balance in the SOL, as it was observed in the simulation that there was a large deviation from a simple total pressure balance (the sum of ion and electron static pressure plus ion inertia). It will be shown that both the contributions from the ion viscosity (driven by ion temperature anisotropy) and neutral source terms can be substantial, and should be retained in the parallel momentum equation in the SOL, but still falls short of accounting for the observed fluid pressure imbalance in the XGCa simulation results.

A Static Low Energy Ion Source for Local Surface Modification

Journal Article A Static Low Energy Ion Source for Local Surface Modification Get access Johannes J L Mulders, Johannes J L Mulders FEI Company, Achtseweg Noord 5, 5600KA Eindhoven, The Netherlands Search for other works by this author on: Oxford Academic Google Scholar Petrus HF Trompenaars Petrus HF Trompenaars FEI Company, Achtseweg Noord 5, 5600KA Eindhoven, The Netherlands Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 22, Issue S3, 1 July 2016, Pages 630–631, https://doi.org/10.1017/S1431927616004001 Published: 25 July 2016

Generalized model screening potentials for Fermi-Dirac plasmas

In this paper, some properties of relativistically degenerate quantum plasmas, such as static ion screening, structure factor, and Thomson scattering cross-section, are studied in the framework of linearized quantum hydrodynamic theory with the newly proposed kinetic γ-correction to Bohm term in low frequency limit. It is found that the correction has a significant effect on the properties of quantum plasmas in all density regimes, ranging from solid-density up to that of white dwarf stars. It is also found that Shukla-Eliasson attractive force exists up to a few times the density of metals, and the ionic correlations are seemingly apparent in the radial distribution function signature. Simplified statically screened attractive and repulsive potentials are presented for zero-temperature Fermi-Dirac plasmas, valid for a wide range of quantum plasma number-density and atomic number values. Moreover, it is observed that crystallization of white dwarfs beyond a critical core number-density persists with this new kinetic correction, but it is shifted to a much higher number-density value of n0 ≃ 1.94 × 1037 cm−3 (1.77 × 1010 gr cm−3), which is nearly four orders of magnitude less than the nuclear density. It is found that the maximal Thomson scattering with the γ-corrected structure factor is a remarkable property of white dwarf stars. However, with the new γ-correction, the maximal scattering shifts to the spectrum region between hard X-ray and low-energy gamma-rays. White dwarfs composed of higher atomic-number ions are observed to maximally Thomson-scatter at slightly higher wavelengths, i.e., they maximally scatter slightly low-energy photons in the presence of correction.

Choline salicylate ionic liquid by X-ray scattering, vibrational spectroscopy and molecular dynamics

We report here a combined experimental and theoretical study on the bio-compatible salicylate choline ionic liquid. The liquid structure has been investigated by X-ray diffraction and vibrational (IR and Raman) spectroscopy. Local structure has been obtained from ab initio calculations on static ion pairs and from dynamic simulations of a small portion of the liquid. The theoretical models indicate that salicylate is connected by hydrogen bonding to choline mainly through the carboxylate group and forms stable ion pairs. A strong intramolecular interaction hinders internal rotations of the OH group of salicylate and competes with the hydrogen bonding with choline. When the liquid has been simulated by classical force fields we found a good agreement with the X-ray experimental features, comparable to that obtained from AIMD simulations. Important insights on hydrogen bonding between carboxylate and choline have been also derived from the analysis of the CO stretching modes of carboxylate measured in the Raman and IR spectra and calculated from VDOS-Wannier centers procedures.

Regularities of Sorption of Cations of Zinc and Copper by Natural Sorbent

Basic laws of static ion exchange of copper cation (II) zinc from aqueous caustic by natural mineral kaolinite were investigated. Quantitative characteristics of sorption process of copper ions and zinc were obtained. The sorption capacity of kaolinite was studied at temperatures of 298, 318, and 333K (mmol/g): for copper ions of 0.55 (at 298K) 0.60 (318K), 0.70 (333K), and for zinc ions of 0.38 (298K), 0.45 (318K), 0.53 (333K). The nature of interaction between the sorbate and sorbent is established. Balance of copper and zinc ions exchange on kaolinite by method of isotherms creation was investigated. It is established that isotherms belong to Lengmuir isotherms and according to BET classification they have the I type at copper ions sorption, and the IV type at zinc ions sorption. It is shown that the sorption parameter of interaction (K) characterizes the energy of interaction of copper ions with the sorbent.

Structural studies on choline-carboxylate bio-ionic liquids by x-ray scattering and molecular dynamics.

We report a X-ray diffraction and molecular dynamics study on three choline-based bio-ionic liquids, choline formate, [Ch] [For], choline propanoate, [Ch][Pro], and choline butanoate, [Ch][But]. For the first time, this class of ionic liquids has been investigated by X-ray diffraction. Experimental and theoretical structure factors have been compared for each term of the series. Local structural organization has been obtained from ab initio calculations through static models of isolated ion pairs and dynamic simulations of small portions of liquids through twelve, ten, and nine ion pairs for [Ch][For], [Ch][Pro], and [Ch][But], respectively. All the theoretical models indicate that cations and anions are connected by strong hydrogen bonding and form stable ion pairs in the liquid that are reminiscent of the static ab initio ion pairs. Different structural aspects may affect the radial distribution function, like the local structure of ion pairs and the conformation of choline. When small portions of liquids have been simulated by dynamic quantum chemical methods, some key structural features of the X-ray radial distribution function were well reproduced whereas the classical force fields here applied did not entirely reproduce all the observed structural features.

Delivery validation of VMAT stereotactic ablative body radiotherapy at commissioning

Dosimetric validation of two volumetric modulated arc therapy (VMAT) stereotactic ablative radiotherapy (SABR) plans was completed as part of the commissioning process of this technique in our clinic. Static and dynamic ion chamber, EBT3 film and leuco crystal violet (LCV) micelle gel measurements were acquired using a motion phantom with appropriate inserts for each dosimeter. The results show good agreement between measured and calculated plan dose.

Prospect of increasing secondary ion yields in ToF‐SIMS using water cluster primary ion beams

Low ionization yields in time of flight secondary ion mass spectrometry (ToF‐SIMS) particularly from single cells and tissues are proving to be a significant limitation in allowing this technique to reach its full potential. A number of approaches including embedding the sample in water or spraying water above sample surface has shown great prospective for increasing the ionization yield by a factor of 10 to 100 through ‘proton mediated’ reaction. Based on this hypothesis, a water cluster primary ion source has been developed in collaboration with Ionoptika Ltd to generate giant water cluster ions (H2O)n+ (n = 1−10 000) using a similar supersonic jet expansion methodology as for argon cluster beams. The ion yields of arginine, cholesterol, angiotensin II and a lipid mix have been measured under static and high ion dose conditions using (H2O)5000+, (H2O)3000+, Ar3000+ and C60+ primary ion beams at 20 keV. An enhancement in yields up to a factor of around 4 is observed under water cluster impact, in comparison with C60+ at 1 × 1011 ions/cm2 ion dose, whereas this increases by around 10–50 times at high ion dose conditions. Copyright © 2014 John Wiley & Sons, Ltd.

On the characteristics of head on collision of dust ion acoustic solitons in the adiabatic dusty plasmas

Based on a one-dimensional mode, the characteristics of the head on collision between two dust ion acoustic solitons (DIASs), propagating in opposite directions in adiabatic dusty plasmas composed of adiabatic non-inertial electrons, adiabatic inertial ions and immersed (negatively/positively) charged dust grains have been investigated. The extended Poincaré–Lighthill–Kuo (PLK) method has been used to obtain two side Korteweg-de Vries (KdV) equations for DIASs. The analytical phase shifts and trajectories after collision of two solitons are given. The effects of adiabaticity of electron and ion fluids, concentration of negatively/positively charged static dust particles and ion temperature to electron temperature ratio on the phase shift are studied. It is found that these factors significantly affect the phase shifts.

Environmentally friendly preparation of a strong basic anion exchange fibers and its application in sugar decolorization

An efficient route for the synthesis of a strong basic anion exchange fibers is described. In this synthesis route, the commercially available p-chloromethylstyrene was directly grafted onto a polypropylene fiber substrate, which eliminated the need of the highly carcinogenic chloromethyl methyl ether in the chloromethylation of grafting fiber. Several interdependent parameters such as monomer concentration, bath ratio and the influence of solvents on the grafting copolymerization were investigated. The removal efficiency of sugar colorants by the anion exchange fibers was evaluated. The results show that simultaneous irradiation and grafting p-chloromethylstyrene onto polypropylene fiber can obtain a good grafting level under appropriate conditions. The optimal monomer concentration and bath ratio are 40% and 1:30 for a moderate grafting degree and the suitable solvent is toluene. The grafted fiber changed from flexible to rigid. And the prepared material maintains stable before 134.5°C. The static ion exchange capacity of the synthesized anion exchange fiber is up to 4.72mmolg−1 and the fiber possesses better ability to remove sugar colorants. The experimental results indicate that the decolorization ratio of the product anion exchange fibers was greater than that of commercial material.

Stokes shift dynamics of ionic liquids: Solute probe dependence, and effects of self-motion, dielectric relaxation frequency window, and collective intermolecular solvent modes

In this paper we have used a semi-molecular theory for investigating the probe dependence of Stokes shift dynamics in room temperature ionic liquids (ILs) by considering three different but well-known dipolar solvation probes--coumarin 153, trans-4-dimethylamino-4(')-cyanostilbene, and 4-aminophthalimide. In addition, effects on polar solvation energy relaxation in ILs of solute motion, frequency coverage (frequency window) accessed by dielectric relaxation measurements and collective IL intermolecular modes (CIMs) at tera-hertz range have been explored. Eleven different ILs have been considered for the above theoretical study. Calculated results show better agreement with the recent (fluorescence up-conversion (FLUPS) + time-correlated single photon counting (TCSPC)) experimental results, particularly at short times, when the CIM contribution to the frequency dependent dielectric function (ɛ(ω)) is included. This is done via assigning the missing dispersion in an experimental ɛ(ω) to an IL intermolecular mode at 30 cm(-1). No significant probe dependence has been observed for solvation energy relaxation although the magnitude of dynamic Stokes shift varies with the dipole moment of the excited solute. Calculations using experimental ɛ(ω) measured with broader frequency window generate solvation response functions closer to experiments. However, average solvation rates predicted by using different ɛ(ω) for the same IL do not differ appreciably, implying over-all validity of these dielectric relaxation measurements. Results presented here indicate that inclusion of solvent molecularity via wavenumber dependent static correlations and ion dynamic structure factor relaxation improves significantly the comparison between theory and experiments over the continuum model predictions for polar solvation dynamics in these solvents.

Refining the glycerin phase from palm‐oil biodiesel by ion‐exchange with cationic resins

AbstractBackgroundGlycerin is produced as an 11% by‐product in biodiesel manufacturing. Impurities are concentrated in the glycerin phase. High‐vacuum distillation of glycerin is an energy‐intensive process. A new low‐cost purification strategy for glycerin is needed. This paper reports the refining of the glycerin phase obtained from palm‐oil biodiesel synthesis by ion‐exchange with cationic resins. In the literature and to the best of the authors' knowledge, the use of a real glycerin phase from biodiesel has not been reported. The ion‐exchange equilibrium was determined in a batch process, while variables for the industrial scaling‐up were studied in continuous operation.ResultsThe sodium content obtained with low amounts of resin is lower than that obtained with mineral‐acid refining. Almost complete sodium removal could be achieved in continuous operation. Langmuir and Freundlich models give a good fit to the equilibrium data. Amberlyst was the best resin. Breakthrough capacity was 96% of static exchange capacity. 95% of the static ion exchange was recovered by washing with water‐soap.ConclusionA 96.6% purification level of glycerol was obtained with the resin Amberlyst 15, using a methanol content of 60%, liquid phase flow of 0.8 mL min−1 and 0.3 g resin g−1 glycerin phase; dynamic exchange capacity was 96% of the static exchange capacity. Exchange capacity is almost completely regenerated by washing with water‐soap. © 2013 Society of Chemical Industry

Binding energy levels of a slowly moving ion in dusty plasmas

The near field electric potential of a slowly moving ion in complex plasmas is studied. We find that the potential consists of the Debye-Hückel potential, the wake potential, and the potential associated with charge fluctuations. The binding energy levels of the ion are calculated by use of the Ritz variation method. The results show that the binding energy levels are related to the magnetic quantum number m. The binding energy levels are affected by speed of the ion and dust grain number density. In contract to isolated ion or static ion in plasmas, the binding energy levels of the ion are pushed up and even become unbounded.

SU‐E‐T‐369: Evaluation of Dose Control System Performance on a TomoTherapy Hi‐Art System

Purpose: TomoTherapy Hi'¢Art systems may exhibit rotational dose fluctuation and dose drift during treatment delivery. A dose servo system has been developed by Accuray, Inc. to monitor and control the dose output on TomoTherapy Hi'‐Art systems. The Dose Control System (DCS) provides continuous control of the linear accelerator output through a closed loop control system to maintain a constant dose output. The purpose of this study is to evaluate the clinical performance of the DCS and to quantify the stability of the dose output after the installation of DCS on our Hi'¢Art unit. Methods: Daily ion chamber measurements in a solid water phantom for static and IMRT deliveries were compared for a time period of two months before and after the DCS installation. Weekly beam measurements using onboard MVCT detector and ion chamber data acquired by field service engineers were also analyzed. Dose stability and intra‐procedure dose drift were assessed from data before and after the DCS installation. Results: Both the range and standard deviations of daily static and IMRT ion chambermeasurements improved with the DCS. The standard deviation of the daily IMRT measurements improved from 0.96% to 0.5%. The dose drift also improved significantly with the DCS. The intra‐dose dose drift during a 200 second rotating procedure decreased from an average of 1.02% to 0.02% based on on‐board ion chamber data. The data show that the dose output is much more stable overall and more consistent from day to day. Conclusions: Based on dosimetric QA endpoints, the DCS has shown a marked improvement in machine dose stability and intra‐procedure dose drift when compared to data from before DCS was installed. MD Anderson Cancer Center Orlando holds a research grant from Accuray, Inc.