Total Number Of Ions Research Articles

Study of the delayed pumping effect in the underground laboratory by the method of correlation analysis of radon and aeroion concentrations

Measurements and correlation analysis of radon and aeroion concentrations in the underground laboratory were carried out. For pairs of variables “pressure — radon” and “pressure — ions”, a delayed pumping effect was found, similar to that previously observed for neutrons and gamma quanta. A simple phenomenological model explaining the results is presented. In this model, the reason for the delay is the gradual accumulation of radon in the room with a decrease in atmospheric pressure. The balance of the radon accumulation rate, the time of its radioactive decay and the characteristic time of pressure variations leads to an effective delay of 2 days between atmospheric pressure variations and radon concentration. Correlation analysis for the variables “pressure — ions” indicates that ions formed in the pores of the soil are already present in the air carrying radon to the laboratory. These ions make up approximately 21% of the total number of ions in the laboratory.

Molecular dynamics simulation on thermophysical properties and local structure of ternary chloride salt for thermal energy storage and transfer system

Ternary chloride salt (NaCl–KCl–MgCl2) is considered as a potential high temperature thermal storage material owing to its low melting point, excellent thermal properties and low cost. However, the thermophysical properties of ternary chloride salts are difficult to measure under high-temperature conditions. In this study, the microscopic model of ternary chloride salt is constructed by Materials Studio software. The ratio of Na ions, K ions, Mg ions and Cl ions in the simulation system is determined according to the molar ratio of NaCl–KCl–MgCl2 eutectic ternary chloride salt. The total number of ions is identified based on computational resources and the accuracy of simulation results, and the number of the four ions in the system is finally determined. LAMMPS software is used to simulate the microstructure and calculate the thermal properties. Simulation results indicate that as the temperature increases, the distance between cluster ions increases, while the coordination number decreases, resulting in the ion association weakens. Simulation results of thermophysical properties are in good agreement with the experimental measurements. The decrease in density and viscosity is attributed to the weakening of ion association with increasing temperature. All the results are expected to provide reliable guidance for the design and preparation of next-generation concentrating solar thermal energy storage materials.

Reducing ion diffusion at atmospheric pressure through intermingled positive and negative ions

Increasing ion molecule reaction times for ambient ionization techniques can increase sensitivity of detection. Longer reaction times result in an increase in analyte signal relative to the reactant ion signal, however with a subsequent decrease in the total ion intensity. This loss in the total number of ions reaching the detector limits the extent to which increased reaction time can improve detection in practical applications. In this study ion loss was measured using either electric fields or gas flow to control ion transit time. Ion transit times ranged from 40 ms to 8 s, which resulted in ion densities ranging from 5 × 106 to 2 × 104 ions/cm3, respectively. These results provide insights into practical reaction time limitations or experimental boundaries when exploring sensitivity enhancements in ambient ionization. When exploring longer reaction times with an atmospheric flow tube coupled to a mass spectrometer (AFT-MS), an additional corona discharge ionization source of the same polarity was added in an attempt to increase total ion signal, but no improvement in signal was observed. This observation suggested that there was a maximum ion density being reached by the corona discharge that could not be increased by adding more of the same polarity ions. A hypothesis was that intermingling both polarities of ions would reduce ion loss and increase the measured ion signal. When two corona discharge sources—one each of positive and negative polarity—were used simultaneously in an AFT-MS, the total ion signal of either polarity measured by the MS was approximately double the current from a single corona discharge source. An increase in the negative ion signal was also observed when ∼10 parts-per-trillion vapor levels of an explosive (RDX, also known as hexogen) were introduced. In this case both the nitrate reactant ions and the RDX signal more than doubled with the addition of a corona discharge source producing positive ions. When intermingling positive and negative ions, an increase in ion current was also observed when the AFT was coupled directly to a Faraday detector or to an ion mobility spectrometer (IMS). This was the first demonstration of interfacing the AFT to an IMS. The observations and developments from this work will help in creating more portable instruments with improved sensitivity for detection of chemicals.

Next generation multimodal chromatography resins via an iterative mapping approach: Chemical diversity, high-throughput screening, and chromatographic modelling

Multimodal chromatography resins are becoming a key tool in the purification of biomolecules. The main objective of this research was the establishment of an iterative framework for the rapid development of new multimodal resins to provide novel selectivity for the future purification challenges. A large chemically diverse virtual library of 100 multimodal Capto™ MMC ligand analogues was created, and a broad array of chemical descriptors were calculated for each ligand in silico. Principal component analysis (PCA) was used to map the chemical diversity and guide selection of ligands for synthesis and coupling to the Capto ImpRes agarose base matrix. Twelve new ligands were prepared in two groups: ‘group one’ consist of L00-L07 and ‘group two’ consist of L08-L12. These ligands are diverse in the influence of varied secondary interactions such as hydrophobic interactions, H-bonding, etc. Additional resin prototypes were also prepared to look at the chromatographic impact of ligand density variation. High-throughput plate-based studies were performed for parallel resin screening for batch-binding of six model proteins at different chromatographic binding pH and sodium chloride concentration conditions. Principal component analysis of the binding data provided a chromatographic diversity map leading to the identification of ligands with improved binding. Further, the new ligands have improved separation resolution between a monoclonal antibody (mAb1) and product related impurities, a Fab fragment and high molecular weight (HMW) aggregates, using linear salt gradient elutions. To quantify the importance of secondary interactions, analysis of the retention factor of mAb1 on the ligands at various isocratic conditions lead to estimations of (a) the total number of water molecules and counter salt ions released during adsorption, and (b) hydrophobic contact area (HCA). The iterative mapping approach of chemical and chromatography diversity maps described in the paper proves to be a promising method for identifying new chromatography ligands for biopharmaceutical purification challenges.

Simulations of lithium impurity transport with a liquid lithium divertor using EMC3-EIRENE and ITCD

Simulations of lithium (Li) impurity transport behaviour with a liquid lithium divertor on the EAST tokamak have been performed using the fluid code EMC3-EIRENE and the Monte Carlo code ITCD. The interactions between particles and the wall surface, like the gyration-induced scrape-off effect, sheath acceleration, kinetic self-sputtering and reflection, are typically ignored or simplified in fluid models. In order to uncover the impacts of the scrape-off effect, sheath acceleration, kinetic self-sputtering and reflection on Li distribution, detailed analysis of the density distributions of Li1+ and Li2+ ions at the divertor region have been carried out by ITCD modelling. The newly-upgraded ITCD code can principally reproduce the distribution patterns of Li ions as well as EMC3-EIRENE under identical plasma conditions on EAST. However, due to the scrape-off effect and sheath acceleration, the densities of Li1+ and Li2+ ions simulated by ITCD are evidently reduced compared to the EMC3-EIRENE simulations. The kinetic self-sputtering by redeposited Li particles in ITCD can increase the densities of the Li ions. Moreover, the kinetic reflection database calculated by SRIM code has been employed by ITCD, which leads to an increase in the Li densities compared to the reflection approach used in EMC3-EIRENE. Overall, by adding the aforesaid physical effects in ITCD, the total number of Li ions shows an obvious reduction compared to the EMC3-EIRENE modelling.

Analysis and simulation of time-of-flight spectrum in Rb<sup>+</sup>-Rb hybrid trap

The time-of-flight mass spectrum of charged particles, which are created through two-step cw-laser photoionization of laser-cooled <sup>87</sup>Rb atoms in an ion-neutral hybrid trap, is quantitatively investigated to further facilitate the study of Rb<sup>+</sup>-Rb reactive collisions. A microchannel plate (MCP) is used to detect charged particles, and two spectral peaks corresponding to the <sup>87</sup>Rb<sup>+</sup> ions and the product <inline-formula><tex-math id="Z-20230423060254-1">\begin{document}$ \rm {}^{87}Rb_2^+ $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20222273_Z-20230423060254-1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="9-20222273_Z-20230423060254-1.png"/></alternatives></inline-formula> of the Rb<sup>+</sup>-Rb reaction were observed in the time-of-flight spectrum, respectively. The two peaks overlapped with each other and both showed an asymmetric profile. The information about the intensity, position, and half-width of the peak for a specific ion species was derived by fitting the time-of-flight spectrum with the probability density function of the Gumbel distribution. Then the relative ion intensity was converted into absolute ion number through the following steps. The rate equation of the total number of ions, which includes the number of atoms, the calibration factor of MCP, and the effective decay rate of ions in the ion trap, was established by modeling the photoionization of atoms. Combined with the absolute number of atoms measured by absorption imaging, the calibration factor in converting the ion intensity into the ion number was derived and the relative ion intensity was converted into the absolute number of ions. This provides a method of calibrating the MCP. The reliability of our calibration method was proved by the fact that the calibration factor in converting the intensity measured by MCP into particle number is independent of the duration of photoionization, the intensity and wavelength of the ionizing laser. Moreover, in order to explain the relationship between the peak width and temperature of the corresponding ion species, the time-of-flight spectra of the ions trapped in the ion trap were simulated by using COMSOL Multiphysics. The simulation results demonstrated that the large ion kinetic energy results in a narrow spectral peak. In sum, we quantitatively analyze and simulate the time-of-flight spectrum of the photoionization of cold atoms in the Rb<sup>+</sup>-Rb hybrid trap. The absolute number of ions is obtained by the intensity of the spectral peak, and the width of the spectral peak is related to the temperature of the ions. These results lay a foundation for the in-depth analysis of the ion-atom reaction collision and charged particle temperature relaxation in the photoionization of cold atoms, and thus further elucidating the subsequent collisional dynamics of ultracold plasmas.

Negative corona discharge mechanism in C4F7N–CO2 and C4F7N–N2 mixtures

Due to their good dielectric properties and low global warming potential, C4F7N–CO2 and C4F7N–N2 mixtures have shown promising potential to replace SF6 in high voltage gas insulated equipment. However, during manufacturing, installation, and transportation of power equipment, burs and metal particles can be inevitably left inside, and they can cause corona discharge. Fundamental investigation of the corona discharge mechanism is essential to monitor partial discharge signals in environmentally friendly power equipment. This paper applies the fluid model to investigate the discharge mechanism of C4F7N–CO2 and C4F7N–N2 mixtures in negative point-plane corona discharge. A 2D axisymmetric model combines the drift-diffusion equations for electrons, positive ions, and negative ions and Poisson’s equation to study the process of dynamics. The gas is a mixture of C4F7N (5%, 7%, or 13%) and CO2 or N2 (95%, 93%, or 87%). The rise time of the first discharge pulse in C4F7N–CO2 and C4F7N–N2 mixtures is about 0.1 ns. The interval time between the first and the second pulse in the 5% C4F7N–95%CO2 mixture is about 1.5 times longer than that in the 5% C4F7N–95% N2 mixture. When the C4F7N content is 7% and 13%, the interval time between the first and second pulses in C4F7N–CO2 mixtures is about 2 and 3 times longer than those in C4F7N–N2 mixtures, respectively. The suppression regions in C4F7N–CO2 mixtures are larger than those in corresponding C4F7N–N2 mixtures. The total number of electrons, positive ions, and negative ions in C4F7N–CO2 mixtures is higher than that in C4F7N–N2 mixtures, while the reduced electric field in C4F7N–CO2 mixtures is smaller than that in C4F7N–N2 mixtures.

Modeling the modulation characteristics of the Bradbury-Nielsen gate in ion mobility spectrometers.

The Bradbury-Nelson gate (BNG) is a common device used for ion control in time-of-flight mass spectrometry and ion mobility spectrometry (IMS). A dual-location control model was employed in order to better understand the behavior of ions around a modulated BNG. This model illustrated that the ions are released from the starting location and truncated at the cutoff location. The shapes of the starting and cutoff locations are both curved with similar curvature, and the cutoff location is situated further back. Therefore, the distance between the two locations is a key parameter leading to the ion loss during modulation and is influenced by the gating voltage difference. Through simulations and experiments, the ion loss is verified to increase with the increase in the gating voltage difference. Taking a Fourier transform IMS as an example, by reducing the gating voltage difference from 150 to 50V, the signal-to-noise ratio of the time domain result was improved from 91.7 to 386.5 and the resolving power was improved from 40.9 to 63.6. In addition, the superposition effect of multicycle modulation is shown and explained by the model. When the modulated frequency is too rapid and the closing time is insufficient for all the ions to be consumed, some ions continue to exist between the two locations, and the residual ions then enter the drift region during the next few cycles. This phenomenon needs to be avoided because the total number of ions entering the drift region will then increase uncontrollably.

Radical fragment ions in collision-induced dissociation-based tandem mass spectrometry

Collision-induced dissociation (CID) is a common fragmentation strategy in tandem mass spectrometry (MS2) analysis. A conventional understanding is that fragment ions generated in low-energy CID should follow the even-electron rule. As such, (de)protonated ([M+H]+/[M−H]−) or even-electron precursor ions should follow heterolytic cleavages and predominately generate even-electron fragment ions with very few radical fragment ions (RFIs). However, the extent to which RFIs present in MS2 spectra has not been comprehensively investigated. This work uses the annotated high-resolution MS2 spectra from the latest NIST 20 tandem mass spectral library to investigate the occurrence of RFIs in CID MS2 experiments. In particular, RFIs were recognized using integer double bond equivalent (DBE) values calculated from their annotated molecular formulas. Our study shows that 65.4% and 68.8% of MS2 spectra of even-electron precursors contain at least 10% RFIs by ion-count (total number of ions) in positive and negative electrospray ionization modes, respectively. Furthermore, we classified chemicals based on their compound classes and chemical substructures, and calculated the percentages of RFIs in each class. As expected, compounds that can stabilize the radical site via resonance, such as aromatic and conjugated double bond-containing chemicals, are more likely to form RFIs. We also found four possible patterns of change in RFI percentages as a function of CID collision energy. Finally, we demonstrate that the inadequate consideration of RFIs in most conventional bioinformatic tools might be problematic during in silico fragmentation and de novo annotation of MS2 spectra. This work provides a further understanding of CID MS2 mechanisms, and the unexpectedly large percentage of RFIs suggests that the even-electron rule seems to be challenged in numerous cases where it is disobeyed.

Influence of synergistic effect of Mn valence state and oxygen vacancy concentration on microwave absorbing properties of CaMnO3

The research of microwave absorption material has great significance for solving electromagnetic pollution and military security. Manganite perovskite has huge potential for developing into a fine microwave absorption material due to its adjustable electromagnetic property, while the mechanisms are still being explored. Therefore, we aim to explain the microwave loss mechanism of manganite perovskite with the double exchange interaction of Mn ion. Orthorhombic structure CaMnO3 was effectively synthesized, and the Mn valence state and oxygen vacancy concentration were changed by doping at Ca-site, while the total number of Mn ions remained intact. Ba, Sr, La, Sm, and Ce were the doping ions employed. Analyses revealed that the microwave absorption performance of CMO was linked to the Mn valence state and oxygen vacancy concentration. The Sr-CMO with the optimal microwave attenuation capability had the most Mn3+ ions and its dielectric loss is primarily due to polarization relaxation loss. In the microwave attenuation mechanism of La-CMO, which had the least oxygen vacancy content, conductive loss played a larger role. Through the double exchange interaction of Mn, the synergistic impact altered the microwave absorption performance. Hence, we can manipulate Mn valence state and oxygen vacancy concentration to improve the microwave absorption performance of CaMnO3, and the technique might be applied to other Mn-based absorbents.

Recombination Processes of Multi-Charge Ions of a Laser Plasma

The presence of an obstacle on the path of laser plasma expansion in vacuum leads to an increase in the ion charge multiplicity, an expansion of the energy spectrum, and an increase in the total number of ions. The peculiarities of the interaction with a solid-state obstacle are largely associated with the appearance of a shock wave in it, which affects the course of recombination processes. It is shown that it is possible to control the parameters of a recombining laser plasma by changing the expansion dynamics at later stages using solid-state obstacles.

Molecular-Level Understanding of the Influence of Ions and Water on HMGB1 Adsorption Induced by Surface Hydroxylation of Titanium Implants.

Due to its excellent chemical and mechanical properties, titanium has become the material of choice for orthopedic and dental implants to promote rehabilitation via bone anchorage and osseointegration. Titanium osseointegration is partially related to its capability to form a TiO2 surface layer and its ability to interact with key endogenous proteins immediately upon implantation, establishing the first bone-biomaterial interface. Surgical trauma caused by implantation results in the release of high-mobility group box 1 (HMGB1) protein, which is a prototypic DAMP (damage-associated molecular pattern) with multiple roles in inflammation and tissue healing. To develop different surface strategies that improve the clinical outcome of titanium-based implants by controlling their biological activity, a molecular-scale understanding of HMGB1-surface interactions is desired. Here, we use molecular dynamics (MD) computer simulations to provide direct insight into the HMGB1 interactions and the possible molecular arrangements of HMGB1 on fully hydroxylated and nonhydroxylated rutile (110) TiO2 surfaces. The results establish that HMGB1 is most likely to be adsorbed directly onto the surface regardless of surface hydroxylation, which is undesirable because it could affect its biological activity by causing structural changes to the protein. The hydroxylated TiO2 surface shows a greater affinity for HMGB1 than the nonhydroxylated surface. The water layer on the nonhydroxylated TiO2 surface prevents ions and the protein from directly contacting the surface. However, it was observed that if the ionic strength increases, the total number of ions adsorbed on the two surfaces increases and the protein's direct adsorption ability decreases. These findings will help to understand the HMGB1-TiO2 interactions upon implantation as well as the development of different surface strategies by introducing ions or ionic materials to the titanium implant surface to modulate its interactions with HMGB1 to preserve biological function.

Estimations of edge plasma and impurity performance on HL-2M with EMC3-EIRENE modelling

The three-dimensional edge transport code EMC3-EIRENE has been employed to investigate the edge plasma behavior and carbon impurity transport in the HuanLiuqi-2M (HL-2M) tokamak. It is found that the outboard divertor target has a narrower flux deposition width and therefore undergoes more intense peak heat flux than the inboard one. Detailed analyses of carbon impurity have been performed to obtain deeper insights into the mechanisms of edge impurity transport and mitigation of heat loads. As the increment in upstream density, a larger region in the intrinsic friction force dominant regime has been achieved in divertor region, while less impurity ionization source locates in the thermal force dominant region, and hence a better impurity screening has been obtained. The total power loss induced by carbon impurity shows no significant differences as the upstream density increases when it is higher than 1.5 × 1019 m−3, even though the total number of carbon ions in space obviously decreases. Further study on impacts of the impurity source locations has been performed. The carbon impurity eroded from the vertical part of the outboard target is likely to leak out into the upstream, which is attributed to that the region where the intrinsic friction force dominates is thin. On the other hand, the carbon impurity eroded from the inboard target and the horizontal part of the outboard target is under good control due to the wider region in the intrinsic friction force dominant regime.

Masked Multiplexed Separations to Enhance Duty Cycle for Structures for Lossless Ion Manipulations.

The experimental paradigm of one ion packet release per spectrum severely hinders throughput in broadband ion mobility spectrometry (IMS) systems (e.g., drift tube and traveling wave systems). Ion trapping marginally mitigates this problem, but the duty cycle deficit is amplified when moving to high resolution, long pathlength systems. As a consequence, new multiplexing strategies that maximize throughput while preserving peak fidelity are essential for high-resolution IMS separations [e.g., structures for lossless ion manipulations (SLIMs) and multi-pass technologies]. Currently, broadly applicable deconvolution strategies for Hadamard-based ion multiplexing are limited to a narrow range of modulation sequences and do not fully maximize the ion signal generated during separation across an extended path length. Compared to prior Hadamard deconvolution errors that rely upon peak picking or discrete error classification, the masked deconvolution matrix technique exploits the knowledge that Hadamard transform artifacts are reflected about the central, primary signal [i.e., the true arrival time distribution (ATD)]. By randomly inducing mathematical artifacts, it is possible to identify spectral artifacts simply by their high degree of variability relative to the core ATD. It is important to note that the deweighting approach using the masked deconvolution matrix does not make any assumptions about the underlying transform and is applicable to any multiplexing strategy employing binary sequences. In addition to demonstrating a 100-fold increase in the total number of ions detected, the effective deconvolution of data from 5, 6, 7, and 8-bit pseudo-random sequences expands the utility and efficiency of the SLIM platform.

Coulomb Explosion of the Debye Layer As a Mechanism for the Formation of a High-Energy Ion Flow in the Plasma of a Micropinch Discharge

Flows of ions with energies on the order of megaelectronvolts, which propagate both in the axial direction and in the direction perpendicular to the symmetry axis of the discharge, are recorded in a high-current low inductance vacuum spark. Estimates based on the measurements of the total charge of suprathermal electrons emitted from the region of the waist of the current channel in the axial direction, as well as the total number of ions of the indicated energies show that the recorded ion energies correspond quite well to the value that can be achieved as a result of the Coulomb explosion of the Debye waist layer at the stage preceding the radiation compression.

Model of Cathode Spots Crater Formation and Deuterium Desorption Process on Zirconium Deuterium Electrode

In this article, the model including cathode spot process and deuterium desorption process on zirconium deuterium cathode is developed. Five kinds of particle fluxes on cathode surface and three mechanisms affecting deuterium diffusion in cathode are considered. The model not only describes the deformation of cathode metal, but also describes the variation of deuterium concentration with time. On pure zirconium cathode, the mean charge state is larger but on zirconium deuterium cathode, the total ion number density is larger since there are additional deuterium ions, and simulation results show the discharge currents are very close on the two cathodes, the energy flux density on ZrD0.66 cathode is larger so cathode spot crater develops faster on ZrD0.66 cathode. Ablation rates caused by different mechanisms are calculated and the results show in cathode spot development process, mass loss caused by evaporation is ignored, most of the liquid metal will resolidify on cathode surface, and droplets are the main reason for cathode ablation. The ablation rates due to the ejection of droplets are close to experimental results. The ratios of deuterium ion from different mechanisms in this process are also calculated and it is 93.5% in simulation. Simulation results are in agreement with the other researchers’ works.

Computational capacity of pyramidal neurons in the cerebral cortex

The electric activities of cortical pyramidal neurons are supported by structurally stable, morphologically complex axo-dendritic trees. Anatomical differences between axons and dendrites in regard to their length or caliber reflect the underlying functional specializations, for input or output of neural information, respectively. For a proper assessment of the computational capacity of pyramidal neurons, we have analyzed an extensive dataset of three-dimensional digital reconstructions from the NeuroMorpho.Org database, and quantified basic dendritic or axonal morphometric measures in different regions and layers of the mouse, rat or human cerebral cortex. Physical estimates of the total number and type of ions involved in neuronal electric spiking based on the obtained morphometric data, combined with energetics of neurotransmitter release and signaling fueled by glucose consumed by the active brain, support highly efficient cerebral computation performed at the thermodynamically allowed Landauer limit for implementation of irreversible logical operations. Individual proton tunneling events in voltage-sensing S4 protein α-helices of Na+, K+ or Ca2+ ion channels are ideally suited to serve as single Landauer elementary logical operations that are then amplified by selective ionic currents traversing the open channel pores. This miniaturization of computational gating allows the execution of over 1.2 zetta logical operations per second in the human cerebral cortex without combusting the brain by the released heat.

3D hybrid modelling of the extinction of multiple cathode spots in vacuum

Plasma transport during continuous extinction processes from high-current arcs to full extinction is an important issue in the study of vacuum arcs. However, to describe this transition, the traditional methods, magneto hydrodynamics or particle-in-cell, are limited by either accuracy or efficiency. In this paper, we developed a fully 3D hybrid plasma simulation algorithm to study the extinction process of multiple cathode spots in a vacuum environment. Cathode spots are modelled as independent plasma sources rather than treating the whole cathode surface as an indivisible source. For a better balance between efficiency and accuracy, ions are modelled as particles and electrons are treated as a massless fluid. Using this model, the effects of cut-off time and the locations of cathode spots on the extinction process are studied. The results show that during an extinction process, the total number of ions between the electrodes gradually decreases and the mean velocity of the ions gradually increases. When the current approaches zero, two regions can be observed in the gap: the separated jet region, and the common plasma channel region. The last three surviving cathode spots have significant impacts on the ion distribution at current zero, whose values depend on the distances to them. The closer together the three cathode spots are, the higher the value that the local ion density will reach. In addition, at current zero, the maximum ion density appears near the last extinguished cathode spot.

Nontargeted Screening of Water Samples Using Data-Dependent Acquisition with Similar Partition Searching

A rapid screening method for the detection of nontargeted compounds in surface water samples was developed using MS-MS high-resolution mass spectrometry and data-dependent acquisition. The key parameters for the acquisition method were optimized using five model compounds with diverse chemical characteristics. The parameter selection required optimization between the total number of precursor ions that could be selected in an LC-MS run, the quality of each MS (full range) spectrum, and the quality of each MS-MS fragmentation spectrum. After the acquisition method was optimized, 18 surface water samples from rivers, reservoirs, and effluents from wastewater treatment plants were analyzed, generating 41625 MS-MS spectra in about 14 h. The raw data were then converted into two generic formats using the open-access program MSConvert. A combinatorial approach, similar partition searching (SPS), was then used to putatively identify analytes from the accurate mass of each analyte (adjusted for the adduct mass) and the corresponding MS-MS spectra were obtained. In this approach, the structures of about 250000 common compounds, stored in a large database as mathematical partitions of their exact mass, were compared directly to each MS-MS spectrum. Compounds with a similar mass and retention time were grouped together and labeled as "Analytes", using an Excel Add-In. The isotope ratio data from the MS spectrum, the corresponding MS-MS spectra, and the putative identifications were then imported into an Access relational database to facilitate sorting, searching, filtering, and querying the results. This allowed final inspection to assess confidence of the identifications made through the nontargeted screening.

Influence of He++and Shock Geometry on Interplanetary Shocks in the Solar Wind: 2D Hybrid Simulations

AbstractAfter protons, alpha particles (He++) are the most important ion species in the solar wind, constituting typically about 5% of the total ion number density. Due to their different charge‐to‐mass ratio, protons and He++particles are accelerated differently when they cross the electrostatic potential in a collisionless shock. This behavior can produce changes in the velocity distribution function (VDF) for both species generating anisotropy in the temperature, which is considered to be the energy source for various phenomena such as ion cyclotron and mirror mode waves. How these changes in temperature anisotropy and shock structure depend on the percentage of He++particles and the geometry of the shock is not completely understood. In this paper, we have performed various 2D local hybrid simulations (particle ions, massless fluid electrons) with similar characteristics (e.g., Mach number) to interplanetary shocks for both quasi‐parallel and quasi‐perpendicular geometries self‐consistently including different percentages of He++particles. We have found changes in the shock transition behavior as well as in the temperature anisotropy as functions of both the shock geometry and He++particle abundance: The change of the initialθBnleads to variations of the efficiency with which particles can escape to the upstream region facilitating or not the formation of compressive structures in the magnetic field that will produce increments in perpendicular temperature. The regions where both temperature anisotropy and compressive fluctuations appear tend to be more extended and reach higher values as the He++content in the simulations increases.