Resonance Ejection Research Articles

Mass-selective instability and resonance ejection modes for DIT with rectangular asymmetric wave shape.

We consider the operation of a digital linear ion trap with resonance radial ejection and mass selective instability modes. Periodic wave shape has a positive part with amplitude and duration and negative part with amplitude and duration , where T is the period. The mapping of the stability diagram, calculations of the well's depth and ion oscillations spectra are presented. The process of resonant excitation of ion oscillations by a dipole sinusoidal signal is studied, as well as ion ejection at the stability boundary. The trajectory method is used for this purpose. It is shown that the mass selectivity of dipole excitation is twice as large for rectangular wave shape compared to sinusoidal wave shape. Increasing the diameter of the round rods of the linear trap gives an increase in the resolving power. The possibility of DIT operation in mass-selective instability mode at the boundary point is discussed.

Modeling of a linear ion trap with driving rectangular waveforms.

We consider the operation of a digital linear ion trap with resonant radial ejection. A sequence of rectangular voltage pulses with a dipole resonance signal is applied to the trap electrodes. The periodic waveform is piecewise constant, has zero mean, and is determined by an asymmetry parameter : one value is taken on interval and another on , where is the RF period. Ion mass scanning is performed by varying the asymmetry parameter and amplitude of the negative pulse part with time. The ion oscillation frequencies and acceptance of the linear trap are calculated. The dependence of the ion mass to charge ratio on the parameter is . The maximum value is about kDa for typical parameters of the linear trap: frequency 0.5 MHz, rod radius 4 mm, and negative pulse amplitude 1 kV. The dipolar excitation frequency is 0.125 MHz at which the LIT acceptance is maximal.

Development of a linear ion trap mass spectrometer capable of analyzing megadalton MALDI ions

Detecting megadalton matrix-assisted laser desorption/ionization (MALDI) ions in an ion trap mass spectrometer is a technical challenge. In this study, megadalton protein and polymer ions were successfully measured by MALDI linear ion trap mass spectrometer (LIT-MS) for the first time. The LIT-MS is comprised of a Thermo linear ion trap mass analyzer and a highly sensitive charge-sensing particle detector (CSPD). A newly designed radio frequency (rf) scan mode with dipolar resonance ejection techniques is proposed to extend the mass range of LIT-MS up to one million Thomson (Th). We analyze high mass ions with mass-to charge (m/z) ratios ranging from 100 kTh to 1 MTh, including thyroglobulin, alpha-2-macroglobulin, immunoglobulins (e.g., IgG and IgM), and polymer (∼ 940 kTh) ions. Besides, it is also very challenging for ion trap mass spectrometry to detect megadalton ions at low concentrations. By adopting high affinity carboxylated/oxidized detonation nanodiamonds (oxDNDs) to enrich IgM molecules and form antibody-nanodiamond conjugates, we have successfully reached ∼ 5 nM (5 μg/mL) concentration which is better than that by the other techniques.

Effect of early metoprolol before PCI in ST-segment elevation myocardial infarction on infarct size and left ventricular ejection fraction. A systematic review and meta-analysis of clinical trials.

AimThis meta‐analysis aims to look at the impact of early intravenous Metoprolol in ST‐segment elevation myocardial infarction (STEMI) before percutaneous coronary intervention (PCI) on infarct size, as measured by cardio magnetic resonance (CMR) and left ventricular ejection fraction.MethodsWe searched the following databases: PubMed, Scopus, Cochrane library, and Web of Science. We included only randomized control trials that reported the use of early intravenous Metoprolol in STEMI before PCI on infarct size, as measured by CMR and left ventricular ejection fraction. RevMan software 5.4 was used for performing the analysis.ResultsFollowing a literature search, 340 publications were found. Finally, 18 studies were included for the systematic review, and 8 clinical trials were included in the meta‐analysis after the full‐text screening. At 6 months, the pooled effect revealed a statistically significant association between Metoprolol and increased left ventricular ejection fraction (LVEF) (%) compared to controls (mean difference [MD] = 3.57, [95% confidence interval [CI] = 2.22–4.92], p < .00001), as well as decreased infarcted myocardium(g) compared to controls (MD = −3.84, [95% [CI] = −5.75 to −1.93], p < .0001). At 1 week, the pooled effect revealed a statistically significant association between Metoprolol and increased LVEF (%) compared to controls (MD = 2.98, [95% CI = 1.26−4.69], p = .0007), as well as decreased infarcted myocardium(%) compared to controls (MD = −3.21, [95% CI = −5.24 to −1.18], p = .002).ConclusionA significant decrease in myocardial infarction and increase in LVEF (%) was linked to receiving Metoprolol at 1 week and 6‐month follow‐up.

Adaptation and operation of a quadrupole/time-of-flight tandem mass spectrometer for high mass ion/ion reaction studies

A commercial quadrupole/time-of-flight tandem mass spectrometer has been modified and evaluated for its performance in conducting ion/ion reaction studies involving high mass (>100 kDa) ions. Modifications include enabling the application of dipolar AC waveforms to opposing rods in three quadrupole arrays in the ion path. This modification allows for resonance excitation of ions to effect ion activation, selective ion isolation, and ion parking. The other set of opposing rods in each array is enabled for the application of dipolar DC voltages for the purpose of broad-band (non-selective) ion heating. The plates between each quadrupole array are enabled for the application of either DC or AC (or both) voltages. The use of AC voltages allows for the simultaneous storage of ions of opposite polarity, thereby enabling mutual storage ion/ion reactions. Ions derived from nano-electrospray ionization of GroEL and β-galactosidase under native conditions were used to evaluate limits of instrument performance, in terms of m/z range, ion isolation, and ion storage. After adjustment of the pulser frequency, ions as high in m/z as 400,000 were detected. Significant losses in efficiency were noted above m/z 250,000 that is likely due to roll-over in the ion detector efficiency and possibly also due to limitations in ion transfer efficiency from the collision quadrupole to the pulser region of the mass analyzer. No measurable decrease in the apparent mass resolving power was noted upon charge state reduction of the model ions. Resonance ejection techniques that employ the dipolar AC capabilities of the quadrupoles allow for ion isolation at m/z values much greater than the RF/DC limitation of Q1 of m/z = 2100. For example, at the highest low-mass cutoff achievable in the collision quadrupole (m/z = 500), it is possible to isolate ions of m/z as high as 62,000. This is limited by the lowest dipolar AC frequency (5 kHz) that can be applied. A simple model is included to provide for an estimate of the ion cloud radius based on ion m/z, ion z, and ion trap operating conditions. The model predicts that singly charged ions of 1 MDa and thermal energy can be contained in the ion trap at the maximum low-mass cutoff, although such an ion would not be detected efficiently. Doubly charged GroEL ions were observed experimentally. Collectively, the performance characteristics at high m/z, the functionality provided by the standard instrument capabilities, the modifications described above, and highly flexible instrument control software provide for a highly versatile platform for the study of high mass ion/ion reactions.

Running the gauntlet – survival of small circumbinary planets migrating through destabilizing resonances

ABSTRACT All of the known circumbinary planets are large (Rp ≥ 3 R⊕). Whilst observational biases may account for this dearth of small planets, in this paper we propose a theoretical explanation. Most of the known planets are near the stability limit, interspersed between potentially unstable 5:1, 6:1, and 7:1 mean motion resonances with the binary. It is believed that these planets did not form in situ, but rather migrated from farther out in the disc, and hence passed through these resonances. Planets are expected to migrate at a speed proportional to their mass, and a slower rate makes resonant capture and subsequent ejection more likely. Therefore, whilst large planets may be able to successfully ‘run the gauntlet’, small planets may be imperilled. This hypothesis is tested using N-body integrations of migration in a truncated and turbulent disc. We discover that surprisingly none of the known planets exist interior to a fully unstable resonance. We demonstrate that resonant ejection of migrating planets may occur in nature, and that it does indeed disproportionately affect small planets, but it requires a highly turbulent disc and its efficiency is likely too low to fully explain a dearth of Rp &amp;lt; 3 R⊕ planets.

Extending the mass-to-charge scannable range of a linear ion trap mass spectrometer through quadrupolar direct current scan

Mass scan methods utilizing quadrupolar direct current (DC) scan were described and performed with a linear ion trap (LIT) through a home-built MS apparatus designed for ion/ion reactions. Both quadrupolar DC downscan and upscan are applicable to the LIT due to the shape of the related Mathieu stability diagram. Besides, a supplementary AC signal could be added to the DC scan process for resonant ejection, which largely enhances the signal-to-noise (S/N) ratios of the spectra. Compared with conventional resonance ejection RF scans, the scannable mass-to-charge (m/z) range in quadrupolar DC scan is much wider. Several protein cations were chosen as test molecules with a m/z scannable range larger than 140,000 Th. Besides, compared with three-dimensional (3D) quadrupolar ion traps (QIT), the LIT is a more suitable mass analyzer for ions with large m/z ratios due to large ion capacity and deep pseudopotential well depths for ions inside the trap. In general, DC scan with LIT offers a new way of rapid detection of ions with extra wide m/z scannable ranges, which has potential applications in research fields such as “top-down” proteomics and native mass spectrometry in the future.

Asymmetric rectilinear ion trap with unidirectional ion ejection capability.

In this paper, the shapes of the electrodes are modified based on a rectilinear ion trap to achieve unidirectional ejection of ions. The designed asymmetric rectilinear ion trap (ARIT) analyzer adds convex and concave circular structures with a height of 0.5 mm on the two X-electrodes, so that the electric field center of the ion trap is inclined to the concave side. The electric field lines of the convex side are compressed to the concave side. Both simulations and experimental results show that ions are more likely to emit from the slit on the concave side plate when performing ion resonance ejection. The mass spectrum signal intensity can reach more than twice that of the original rectilinear trap when using only one detector. Calculations of the electric field components in the trap show that the even-order higher field proportion in the ion trap has not been significantly affected. Combined with the experimental test results, the study further confirmed that the developed ARIT has no significant loss in mass resolution, tandem mass spectrometry capability, and quantitative analysis capability. The proposed asymmetric structure modification scheme can achieve single-side ejection without significantly affecting other performances of the analyzer, which provides a new idea for the structural optimization of the subsequent ion trap analyzers.

Enabling Isotope Ratio Measurements on an Ion Trap Mass Spectrometer.

For portable, remotely operated systems in space and defense, relaxed vacuum requirements are a strong advantage of ion trap mass analyzers. However, ion traps are believed to have insufficient capability for isotope ratio measurement because they fundamentally restrict sampling capacity. Focusing on modifications to the detection sequence of a digitally driven 3D quadrupole ion trap, operating in resonance ejection mode, we investigated improved performance for isotope ratio precision and accuracy. Due to xenon's inert nature and wide span of isotopes, xenon isotope ratios provide an excellent marker of processes (e.g. radioactive decay and planetary atmospheric escape) which would be ideally measured by in situ mass spectrometry. To target xenon isotope ratio analysis specifically, we implemented data acquisition system modifications for enhanced y-axis resolution measurements and signal filtering. In this manner, we show measurement precision improvements from ~±100 0/00 to ~±0.1 0/00 and accuracy improvements from ~30 0/00 to ~0.5 0/00 for our targeted isotopes of interest.

Triple Resonance Methods to Improve Performance of Ion Trap Precursor and Neutral Loss Scans.

Two experiments are described that extend the capabilities of quadrupole ion trap mass spectrometers operated in the precursor and neutral loss scan mode. The first experiment, a triple resonance precursor ion scan, is used to enhance sensitivity, selectivity, and molecular coverage. This method augments the ion trap precursor ion scan with the application of a second excitation frequency to selectively activate first-generation (MS2) product ions as they are formed and produce second-generation (MS3) product ions, which are then mass-selectively ejected with a third auxiliary signal and detected. This single mass analyzer experiment can be equated to performing the sequential precursor ion scan in a multiple analyzer system (Anal. Chem. 1990, 62 (17), 1809-1818). The second capability demonstrated is "frequency tagging", a method used to differentiate between ions ejected due to inherent instability under given trapping conditions, which causes artifacts during these scans, and ions that are resonantly ejected by the product ion ejection frequency. Beat frequencies are used to modulate resonance ejection peaks but conveniently do not modulate boundary ejection peaks. Frequency tagging provides a mechanism to identify the artifact peaks that are a consequence of operating at a high trapping voltage (i.e., low mass cutoff) for optimal precursor/product ion selectivity. The experiment is demonstrated for precursor and for neutral loss scans.

Linear and Nonlinear Resonance Ejection of High Mass Ions with charge detection rectilinear ion trap mass spectrometer

We present the linear and nonlinear resonance ejection of high mass-to-charge (m/z) ratio of protein ions with charge detection rectilinear ion trap mass spectrometer (CD RIT-MS). The measurements of ejected high mass ions with dipolar resonance ejection in the presence of high order fields are demonstrated. With linear resonance ejection, it was found the measured ion number could be enhanced by a factor of 3–5 as compared to that with boundary ejection. With nonlinear resonance ejection (with high order fields), e.g. a positive octopolar field, the ion number can be enhanced by a factor of 4–6 as compared to that with boundary ejection. Mass resolution is slightly improved with nonlinear resonance ejection (∼1.4 for cytochrome C ions) as compared to linear resonance ejection and about a factor of 5 improvements as compared to boundary ejection. In addition, when analyzing heavier bovine serum albumin (BSA) ions, it was observed that co-occurrence of boundary and resonance ejection was prominent with respect to m/z values, iso-β points, and auxiliary AC resonance amplitude where the ejection was below an octopolar field point of βu = 0.70.

Digital Mass Analysis in a Linear Ion Trap without Auxiliary Waveforms.

Mass analysis in a linear ion trap is traditionally performed using resonant ejection induced by auxiliary waveforms. For sinusoidally driven ion traps without resonant ejection, resolution and sensitivity are poor because mass-selected instability yields excitation along both the x and y axes simultaneously. Digital ion traps, on the other hand, have the advantage of duty cycle manipulation that can be used to change the ion excitation along the x and y axes. Consequently, the duty cycle can be used to enhance the resolution and sensitivity for mass-selected instability in a linear ion trap without the application of an auxiliary waveform. This work introduces and explores mass-selected instability in a linear trap without the use of auxiliary waveforms.

P5282Comparison of cardiovascular magnetic resonance ejection fraction and left ventricular volumes by long axis feature tracking strain analysis versus standard short axis stack contour tracing

Abstract Introduction Cardiovascular magnetic resonance (CMR) feature tracking (FT) is based on the recognition of endocardial features obtained during standard CMR cine imaging to be tracked and followed throughout the cardiac cycle. Global longitudinal strain (GLS) has been proposed as a superior measure for diagnosis and prognosis than ejection fraction (EF). However, EF remains an important primary parameter to describe cardiac function. A rapid determination of GLS based on three long axis views (LAX) allows for a simultaneous calculation of EF without additional imaging or post-processing promising a significant reduction of scan and post-processing time. Purpose The purpose of this work is to compare the LV volumes and EF obtained during assessment of GLS based on CMR feature tracking with standard analysis of a short axis (SAX) stack used as the reference standard. Methods 75 consecutive patients underwent a routine clinical scan obtaining a full SAX stack as well as 3 standard LAX views using either 3-Tesla or 1,5-Tesla clinical scanners. We determined LV volumes and EF based on the reference standard as well as feature tracking analysis with additional GLS. A p value &lt;0.01 was considered statistically significant. Results Mean EF was 45.9% using standard SAX (range, 13%-72%) and 51.1% using triplanar feature tracking (r=0.950; p&lt;0.0001, figure 1A). Bland-Altman analysis showed a systematic bias of 5,27%; without proportional bias (figure 1B). End-diastolic volumes (r=0,975; p&lt;0.0001) and end-systolic volumes (r=0.985; p&lt;0.0001) demonstrated similar results. Mean GLS was −17.3% (range: −30,7% to −3,3%) and was significantly correlated with standard EF (r=−0,884; p&lt;0.0001). Classification of EF into categories: reduced, mid-range or preserved (&lt;40%, 40–49%, ≥50%) remain unchanged in 79% of patients when using EF by feature tracking analysis. Twelve of 16 reclassifications occurred in the mid-range category. Figure 1 Conclusion There is a good correlation between EF obtained by rapid post-processing of GLS with EF based on a full SAX stack resulting in an identical categorization in 79% of patients. Reduction of EF within the mid-range might be best assesses by the standard SAX stack.

P452Prognostic performance of clinical presentation and cardiac magnetic resonance ejection fraction and late enhancement pattern at basal examination in acute myocarditis

P452Prognostic performance of clinical presentation and cardiac magnetic resonance ejection fraction and late enhancement pattern at basal examination in acute myocarditis

Extended mass range detection with a microscale planar linear ion trap mass spectrometer

An extended mass range covering m/z 70–240 in a microscale (r0 = 800 μm) planar linear ion trap (μPLIT) is demonstrated, enabled by optimization of dipole resonance ejection conditions without increasing trapping voltage or frequency compared with prior results. This represents a significant increase in the measureable mass range of coplanar traps and microscale traps in general. Performance was demonstrated using headspace vapor of octafluorotoluene (OFT) as well as mixture of perflurotributylamine (PFTBA) and OFT. Typical mass resolution of approximately 3 Da (FWHM) was observed.

Relative Impact of Right Ventricular Electromechanical Dyssynchrony Versus Pulmonary Regurgitation on Right Ventricular Dysfunction and Exercise Intolerance in Patients After Repair of Tetralogy of Fallot.

BackgroundThe relative impact of right ventricular (RV) electromechanical dyssynchrony versus pulmonary regurgitation (PR) on exercise capacity and RV function after tetralogy of Fallot repair is unknown. We aimed to delineate the relative effects of these factors on RV function and exercise capacity.Methods and ResultsWe retrospectively analyzed 81 children with tetralogy of Fallot repair using multivariable regression. Predictor parameters were electrocardiographic QRS duration reflecting electromechanical dyssynchrony and PR severity by cardiac magnetic resonance. The outcome parameters were exercise capacity (percentage predicted peak oxygen consumption) and cardiac magnetic resonance ejection fraction (RV ejection fraction). To understand the relative effects of RV dyssynchrony versus PR on exercise capacity and RV function, virtual patient simulations were performed using a closed‐loop cardiovascular system model (CircAdapt), covering a wide spectrum of disease severity. Eighty‐one patients with tetralogy of Fallot repair (median [interquartile range {IQR}] age, 14.48 [11.55–15.91] years) were analyzed. All had prolonged QRS duration (median [IQR], 144 [123–152] ms), at least moderate PR (median [IQR], 40% [29%–48%]), reduced exercise capacity (median [IQR], 79% [68%–92%] predicted peak oxygen consumption), and reduced RV ejection fraction (median [IQR], 48% [44%–52%]). Longer QRS duration, more than PR, was associated with lower oxygen consumption and lower RV ejection fraction. In a multivariable regression analysis, oxygen consumption decreased with both increasing QRS duration and PR severity. CircAdapt modeling showed that RV dyssynchrony exerts a stronger limiting effect on exercise capacity and on RV ejection fraction than does PR, regardless of contractile function.ConclusionsIn both patient data and computer simulations, RV dyssynchrony, more than PR, appears to be associated with reduced exercise capacity and RV systolic dysfunction in patients after TOF repair.

Double resonance ejection using novel radiofrequency phase tracking circuitry in a miniaturized planar linear ion trap mass spectrometer.

Ion trap mass spectrometers are attractive due to their inherent sensitivity and specificity. Miniaturization increases trap portability for in situ mass analysis by relaxing vacuum and voltage requirements but decreases the trapping volume. To overcome signal/resolution loss from miniaturization, double resonance ejection using phase tracking circuitry was investigated. Phase tracking circuitry was developed to induce double resonance ejection in a planar linear ion trap using the β 2/3 hexapole resonance line. Double resonance was observed using phase tracking circuitry. Resolution of 0.5 m/z units and improved signal-to-noise ratio (SNR) compared with AC resonant ejection were achieved. The phase tracking circuitry proved effective despite deviations from a true phase locked condition. Double resonance ejection is a means to increase signal intensity in a miniaturized planar ion trap.

Ventricular Torsion in Young Patients With Single-Ventricle Anatomy

In normal left ventricles, clockwise basal rotation and counterclockwise apical rotation result in systolic torsion. Torsion is important for contractile efficiency and may be especially important in single-ventricle (SV) physiology. However, little is known about torsion in patients with SVs. The aim of this study was to measure torsion in SVs and to determine its relationship with other measures of ventricular function. The hypothesis was that torsion would be decreased in all SVs, most significantly in single right ventricles, and that it would correlate with other measures of ventricular function. A prospective cross-sectional study was performed in 61 patients with SVs undergoing pre- or post-Fontan cardiac catheterization and 30 matched control subjects. Echocardiography, catheterization, and cardiac magnetic resonance imaging were performed under the same anesthetic. Torsion and strain were measured using speckle-tracking echocardiography. Intracardiac pressures, pulmonary vascular resistance, and cardiac magnetic resonance imaging-derived ventricular volume and ejection fraction were measured. Thirty-five patients were left ventricular dominant, 15 were right ventricular dominant, 10 were codominant, and one had indeterminate morphology. Thirty-seven patients were pre-Fontan and 24 were post-Fontan. Patients with SVs had similar overall torsion as control subjects (median, 1.7°/cm vs 1.65°/cm; P= NS); however, they had decreased or reversed basal rotation (-0.32°/cm vs -0.93°/cm, P<.0001) and increased apical rotation (1.45°/cm vs 1.06°/cm, P=.0065). There were no differences on the basis of ventricular dominance or palliative stage. Torsion did not significantly correlate with other echocardiographic, catheter-based, or cardiac magnetic resonance imaging measures of cardiac function. Single left and right ventricles exhibit preserved torsion, mainly because of preserved or increased apical rotation. Possible mechanisms of torsion in single right ventricles include myofiber remodeling and altered ventricular-ventricular interactions. Understanding myocardial deformation in SVs will improve the ability to interpret ventricular function in this precarious population.

Improving the Performances of a "Brick Mass Spectrometer" by Quadrupole Enhanced Dipolar Resonance Ejection from the Linear Ion Trap.

Previously, a miniature mass spectrometer driven by a sinusoidal frequency scanning technique, named as Brick mass spectrometer, was developed in our lab ( Jiang et al. Anal. Chem. 2017 , 89 , 5578 ). The frequency scanning technique enabled miniaturized electronics and broader mass range, but it was also limited in reduced mass resolution and sensitivity due to a relatively low operating radio frequency (rf) voltage in comparison with the conventional voltage scanning technique. To improve performances of the Brick mass spectrometer, a quadrupole enhanced dipolar resonance ejection (QE-dipolar resonance ejection) method was proposed in this work. After optimization, mass resolution and sensitivity of the Brick mass spectrometer could be improved by no less than 2 times, and space charge effects within the ion trap could also be reduced. Furthermore, this QE-dipolar resonance ejection method is effective at elevated pressures, which would potentially allow us to further miniaturize the Brick mass spectrometer by operating it at higher pressures. This method is also applicable to any ion trap operated in either frequency scanning mode or voltage scanning mode and operated in either miniaturized instruments or benchtop instruments.

Stimulated Motion Suppression (STMS): a New Approach to Break the Resolution Barrier for Ion Trap Mass Spectrometry.

Ion trap is an excellent platform to perform tandem mass spectrometry (MS/MS), but has an intrinsic drawback in resolving power. Using ion resonant ejection as an example, the resolution degradation can be largely attributed to the broadening of the resonant frequency band (RFB) between ion motion and driving alternative-current (AC). To solve this problem, stimulated motion suppression (STMS) was developed. The key idea of STMS is the use of two suppression alternative-current (SAC) signals, which both have reversed initial phases to the main AC. The SACs can block the unexpected sideband ion resonances (or ejections), therefore playing a key role in sharpening the RFB. The proof-of-concept has been demonstrated through ion trajectory simulations and validated experimentally. STMS provides a new and versatile means for the improvement of the ion trap resolution, which for a long time has reached the bottleneck through conventional methods, e.g., increasing the radio-frequency (RF) voltage and decreasing the mass scan rate. At the end, it is worth noting that the idea of STMS is very general and principally can be applied in any RF device for the purposes of high-resolution mass analysis and ion isolation. Graphical Abstract ᅟ.