Research on double resonant excitation in a triangular electrode ion trap with asymmetric geometry.

RATIONALE: The triangular electrode linear ion trap with asymmetric geometry has been reported to possess a high ion unidirectional ejection efficiency and a reasonable mass resolution. To further improve its performance, a double resonant excitation method involving a dipolar and a quadrupolar resonant excitation was applied here. METHODS: The dipolar excitation method was carried out by applying a supplementary alternating voltage out of phase to one pair of the electrodes, whereas the quadrupolar excitation (QE) method was carried out by adding a supplementary alternating voltage in phase to another pair of electrodes. Numerical simulations were performed to explore the impact of the frequency difference between the alternating current (AC) and the QE voltage (∆ω), the frequency of the AC voltage (ωAC), and the QE voltage amplitude (VQE). RESULTS: The mass resolution could be improved to ~4700 m / ∆ m $$ \left(m/\Delta m\right) $$ , which was approximately twice compared to that with only dipolar resonant excitation, and the ion unidirectional ejection efficiency could be improved to 97%. Even with a high scan rate of 6000 Da/s, there was minimal loss of mass resolution caused by increased scan rate in double resonant excitation mode. CONCLUSIONS: By employing the double resonant excitation method, the mass resolution could be further increased while maintaining a considerably high ion unidirectional ejection efficiency, which might be a simple and practical approach for developing a high-performance miniature ion trap mass analyzer.

Quantitative Assessment of Mitral Apparatus Geometry Using Dual-Source Computed Tomography in Mitral Regurgitation.

To quantitatively assess the geometric changes in mitral valve apparatus in mitral regurgitation (MR) by dualsource computed tomography (DSCT) and to analyze its impact on MR.The study subjects consisted of 20 controls, 20 patients with mild MR, and 30 patients with moderate to severe MR, all of whom underwent DSCT. The geometric parameters of the mitral valve were measured by CT and compared among the 3 groups. The correlations between DSCT measurements and MR severity were also analyzed.As regurgitation worsened, our results showed progressive enlargements of the mitral annular area, anteroposterior diameter, and mitral valve tenting area at the central level. Moreover, a higher mitral valve sphericity index and longer distance between the heads of the papillary muscles reflected a more outward displacement of the papillary muscles. The mitral annular area and tenting area at the central level had strong correlations with regurgitation severity.DSCT is available to quantitatively assess mitral valve morphology and provide additional information regarding its geometry. The mitral annular area and tenting area at the central level were the strongest determinants of MR severity.

Recent Progress in Covalent Organic Frameworks for Cathode Materials.

Covalent organic frameworks (COFs) are constructed from small organic molecules through reversible covalent bonds, and are therefore considered a special type of polymer. Small organic molecules are divided into nodes and connectors based on their roles in the COF's structure. The connector generally forms reversible covalent bonds with the node through two reactive end groups. The adjustment of the length of the connector facilitates the adjustment of pore size. Due to the diversity of organic small molecules and reversible covalent bonds, COFs have formed a large family since their synthesis in 2005. Among them, a type of COF containing redox active groups such as -C=O-, -C=N-, and -N=N- has received widespread attention in the field of energy storage. The ordered crystal structure of COFs ensures the ordered arrangement and consistent size of pores, which is conducive to the formation of unobstructed ion channels, giving these COFs a high-rate performance and a long cycle life. The voltage and specific capacity jointly determine the energy density of cathode materials. For the COFs' cathode materials, the voltage plateau of their active sites' VS metallic lithium is mostly between 2 and 3 V, which has great room for improvement. However, there is currently no feasible strategy for this. Therefore, previous studies mainly improved the theoretical specific capacity of the COFs' cathode materials by increasing the number of active sites. We have summarized the progress in the research on these types of COFs in recent years and found that the redox active functional groups of these COFs can be divided into six subcategories. According to the different active functional groups, these COFs are also divided into six subcategories. Here, we summarize the structure, synthesis unit, specific surface area, specific capacity, and voltage range of these cathode COFs.

Consistent sparse representations of EEG ERP and ICA components based on wavelet and chirplet dictionaries.

A randomized search algorithm for sparse representations of EEG event-related potentials (ERPs) and their statistically independent components is presented. This algorithm combines greedy matching pursuit (MP) technique with covariance matrix adaptation evolution strategy (CMA-ES) to select small number of signal atoms from over-complete wavelet and chirplet dictionaries that offer best approximations of quasi-sparse ERP signals. During the search process, adaptive pruning of signal parameters was used to eliminate redundant or degenerative atoms. As a result, the CMA-ES/MP algorithm is capable of producing accurate efficient and consistent sparse representations of ERP signals and their ICA components. This paper explains the working principles of the algorithm and presents the preliminary results of its use.