Direct Resolution Research Articles

Quasi‐Homogeneous Integrated Strain Vector Sensors for Natural Human–Machine Interaction

AbstractBody motion capture is a vital approach that underpins natural human–machine interaction. Strain sensors that can detect both motion amplitude and direction are the basis for discerning interactive intent. However, most strain sensors with heterogeneous architecture fail to perceive motion direction accurately. Here, quasi‐homogeneous integrated strain vector sensors are constructed by vertically stacking elastomer meshes with different fiber orientations in order. By varying fiber orientation, the proportion of intrinsic elastic and structural deformation in elastomer mesh can be adjusted, achieving effective regulation of its electromechanical properties. A highly anisotropic elastomer mesh with unidirectional fibers is customized, enabling the strain vector sensors to perceive stretch amplitude and direction simultaneously. Notably, the strain vector sensors demonstrate a minimum directional resolution of 2° and a linear working range of up to 100% strain. The tough bonding between quasi‐homogeneous interlayers ensures high robustness even after 10 000 loading cycles. Moreover, a wearable 3D motion capture system is built that can acquire comprehensive data regarding motions, including amplitudes, directions, and modes, and visually synchronize them in virtual reality. Natural human–machine interaction is achieved by intuitively and effortlessly altering motion amplitudes and directions. This work provides an alternative insight for immersive human–machine interaction in the future.

Continuum of non-targeted data for long term study of complex samples generated by direct infusion ultra-high resolution mass spectrometry.

Non-targeted chemical analysis is a powerful tool for exploration of the unknown chemistry of complex matrices such as food, biological, geochemical, environmental and even extra-terrestrial samples. It allows researchers to ask open, unbiased questions about their system chemistry. Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS) offers these options and has been widely used to study complex mixtures, with its unmatched mass resolution enabling direct infusion methods and eliminating the challenges of chromatographic alignment in large-scale longitudinal projects. In this article, we demonstrate the use of FT-ICR-MS for generating a dataset for hundreds of complex samples with diverse chemistries over a period of 6 years and 32 batches, allowing confident comparison of data between samples from different batches. The resulting chemical database will be continuously expanded in future and retrospectively interrogated to test new hypotheses utilizing data of past projects and new knowledge of coming projects. We discuss the experimental setup and how other researchers could apply the same approaches, which is relevant for wide ranging applications and research fields.

Near-isotropic sub-Ångstrom 3d resolution phase contrast imaging achieved by end-to-end ptychographic electron tomography

Abstract Three-dimensional atomic resolution imaging using transmission electron microscopes is a unique capability that requires challenging experiments. Linear electron tomography methods are limited by the missing wedge effect, requiring a high tilt range. Multislice ptychography can achieve deep sub-Ångstrom resolution in the transverse direction, but depth resolution is limited to 2 to 3 nanometers. In this paper, we propose and demonstrate an end-to-end approach to reconstructing the electrostatic potential volume of the sample directly from the 4D-STEM datasets. End-to-end multislice ptychographic tomography recovers several slices at each tomography tilt angle and compensates for the missing wedge effect. The algorithm is initially tested in simulation with a Pt@Al2O3 core–shell nanoparticle, where both heavy and light atoms are recovered in 3D from an unaligned 4D-STEM tilt series with a restricted tilt range of 90 degrees. We also demonstrate the algorithm experimentally, recovering a Te nanoparticle with sub-Ångstrom resolution.

Stochastic modelling for the effects of micromixing on soot in turbulent non-premixed flames

The impact of micromixing and scalar dissipation rate (SDR) fluctuations on the evolution of soot particle size distribution (PSD) dynamics in non-premixed turbulent flames is investigated within the context of Large Eddy Simulation (LES). To accomplish this, a stochastic approach based on a physicochemical sectional soot model, spatially homogeneous Conditional Moment Closure (CMC) with first-order moment closure, and a stochastic differential equation for the SDR are employed, mimicking the function of an LES sub-grid scale (SGS) combustion model. After linking the magnitude of SDR fluctuations to the LES filter size, it was found that the standard deviation of observables, such as the soot volume fraction and soot number density, decreases rapidly with increasing LES filter size, which can significantly influence the intermittency of soot reproduced by models. Mean conditional expectations are also affected, indicating a closure problem, with the mean soot volume fraction, in particular, showing a decrease of up to 20% in the case considered compared to a direct numerical simulation resolution even when the Pope criterion is satisfied. The influence of SDR fluctuations on the dynamic behaviour of the soot PSD is further discussed under different working assumptions for particle transport, and the role of differential diffusion in soot oxidation- and formation-dominant regions is particularly highlighted. The findings underline the shortcomings of LES-CMC and similar mixture-fraction-based combustion models in capturing the dynamic evolution of soot at the SGS, which has significant implications for modelling the emissions of practical combustion devices. However, this study also offers a framework for better evaluating the effectiveness of these models using numerical experimentation and a stochastic model for the turbulent fluctuations of the micromixing rate.

Late Gadolinium Enhancement CMR with Generative AI

BackgroundLate gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) imaging enables imaging of scar/fibrosis and is a cornerstone of most CMR imaging protocols. CMR imaging can benefit from image acceleration; however, image acceleration in LGE remains challenging due to its limited signal-to-noise ratio. In this study, we sought to evaluate a rapid 2D LGE imaging protocol using a generative artificial intelligence (AI) algorithm with inline reconstruction. MethodsA generative AI-based image enhancement was used to improve the sharpness of 2D LGE images acquired with low spatial resolution in the phase-encode direction. The generative AI model is an image enhancement technique built on the enhanced super-resolution generative adversarial network. The model was trained using balanced steady-state free-precession cine images, readily used for LGE without additional training. The model was implemented inline, allowing the reconstruction of images on the scanner console. We prospectively enrolled 100 patients (55 ± 14 years, 72 males) referred for clinical CMR at 3T. We collected three sets of LGE images in each subject, with in-plane spatial resolutions of 1.5×1.5-3-6 mm2. The generative AI model enhanced in-plane resolution to 1.5×1.5 mm2 from the low-resolution counterparts. Images were compared using a blur metric, quantifying the perceived image sharpness (0 = sharpest, 1=blurriest). LGE image sharpness (using a 5-point scale) was assessed by three independent readers. ResultsThe scan times for the three imaging sets were 15±3, 9±2, and 6±1seconds, with inline generative AI-based images reconstructed time of ~37 ms. The generative-AI-based model improved visual image sharpness, resulting in lower blur metric than low-resolution counterparts (AI-enhanced from 1.5×3 mm2 resolution: 0.3±0.03 vs. 0.35±0.03, P<0.01). Meanwhile, AI-enhanced images from 1.5×3 mm2 resolution and original LGE images showed similar blur metric (0.30±0.03 vs. 0.31±0.03, P=1.0) Additionally, there was an overall 18% improvement in image sharpness between AI-enhanced images from 1.5×3 mm2 resolution and original LGE images in the subjective blurriness score (P<0.01). ConclusionsGenerative AI-based model enhances the image quality of 2D LGE images while reducing the scan time and preserving imaging sharpness. Further evaluation in a large cohort is needed to assess the clinical utility of AI-enhanced LGE images for scar evaluation, as this proof-of-concept study does not provide evidence of an impact on diagnosis.

Scientific Information and Validation Criteria in Kindergarten Teachers: An Exploratory Study in Chile

&lt;p style="text-align:justify"&gt;Teaching is a demanding and complex exercise, exposed to the direct or immediate resolution of multiple problematic situations, whether pedagogical, relational, or socio-affective. The teacher's personal resources are often insufficient to cope with the profession's demands. The research reports that there is a gap between research and educational practice. Hence, the objective of this research was to analyze the criteria used by early childhood educators to attribute validity to the written sources of information that guide their pedagogical decisions. The present study follows a qualitative research methodology. The sample for this study was non-probabilistic and consisted of 18 early childhood educators who participated through semi-structured interviews and discussion groups. The data obtained were analyzed by inductive categorization using NVivo 14. The findings revealed that the validity criteria assigned by the educators about the sources of information related to theoretical aspects is mainly attributed to the texts and authors they know, while those referring to practical aspects are attributed to their own experiences or the other educators at the same level. The results showed that specific information and obtaining it in the shortest possible time were the criteria that determined the use of information sources.&lt;/p&gt;

Optimization of 3D imaging time reduction by assessing spatial resolution in the slice selective direction using the ladder method

PurposeAssessing spatial resolution in MRI is challenging due to non-linearity. Despite the widespread use of 3D imaging in clinical practice for lesion detection and multi-planar reconstruction (MPR), the extended acquisition time poses a shortcoming. To address this, the “Slice resolution” parameter is utilized; however, its impact on MPR images is unclear. This study aims to assess spatial resolution using the ladder method, investigate the effects of diverse slice resolution settings in various imaging sequences, and propose optimal conditions. MethodsImages were acquired using various 3D imaging sequences—SPACE T1WI, SPACE T2WI, and VIBE T1WI—with different slice resolutions. Axial cross-section images were acquired and reconstructed into coronal cross-sections. The ladder method was employed for objective evaluation, including spatial frequency analysis. Additionally, visual evaluation was conducted and compared with ladder method results. ResultsFor three imaging sequences, the evaluated value of ladder method remained relatively constant from 100 % to 80 % slice resolution. However, the evaluated value decreased in low-spatial frequency for slice resolution below 70 %. ConclusionsResults from both ladder method and visual evaluations indicated image quality remained stable when the slice resolution was decreased to 80 %, potentially enabling a 20 % reduction in imaging time while preserving resolution in other cross-sections reconstructed by MPR.

Optical microscope with nanometer longitudinal resolution based on a Linnik interferometer

Abstract A widefield microscope based on a Linnik interferometer was designed, constructed, and tested. The phase-shifting and polarized single-shot methods were used to measure interference patterns. Both methods use a low-coherence light-emitting diode as the light source, achieving a resolution of 10 nm in the Z direction and diffraction-limited resolution in the X and Y directions. The single-shot method is vibration-insensitive, allowing for the observation of moving objects. The simplicity and low cost of this instrument make it valuable for a wide range of applications.

A novel GAN-based three-axis mutually supervised super-resolution reconstruction method for rectal cancer MR image

Background and objectiveThis study aims to enhance the resolution in the axial direction of rectal cancer magnetic resonance (MR) imaging scans to improve the accuracy of visual interpretation and quantitative analysis. MR imaging is a critical technique for the diagnosis and treatment planning of rectal cancer. However, obtaining high-resolution MR images is both time-consuming and costly. As a result, many hospitals store only a limited number of slices, often leading to low-resolution MR images, particularly in the axial plane. Given the importance of image resolution in accurate assessment, these low-resolution images frequently lack the necessary detail, posing substantial challenges for both human experts and computer-aided diagnostic systems. Image super-resolution (SR), a technique developed to enhance image resolution, was originally applied to natural images. Its success has since led to its application in various other tasks, especially in the reconstruction of low-resolution MR images. However, most existing SR methods fail to account for all anatomical planes during reconstruction, leading to unsatisfactory results when applied to rectal cancer MR images. MethodsIn this paper, we propose a GAN-based three-axis mutually supervised super-resolution reconstruction method tailored for low-resolution rectal cancer MR images. Our approach involves performing one-dimensional (1D) intra-slice SR reconstruction along the axial direction for both the sagittal and coronal planes, coupled with inter-slice SR reconstruction based on slice synthesis in the axial direction. To further enhance the accuracy of super-resolution reconstruction, we introduce a consistency supervision mechanism across the reconstruction results of different axes, promoting mutual learning between each axis. A key innovation of our method is the introduction of Depth-GAN for synthesize intermediate slices in the axial plane, incorporating depth information and leveraging Generative Adversarial Networks (GANs) for this purpose. Additionally, we enhance the accuracy of intermediate slice synthesis by employing a combination of supervised and unsupervised interactive learning techniques throughout the process. ResultsWe conducted extensive ablation studies and comparative analyses with existing methods to validate the effectiveness of our approach. On the test set from Shanxi Cancer Hospital, our method achieved a Peak Signal-to-Noise Ratio (PSNR) of 34.62 and a Structural Similarity Index (SSIM) of 96.34 %. These promising results demonstrate the superiority of our method.

Capillary electrochromatography applied to the separation of enantiomers utilizing packed capillary columns with silica-vancomycin. A tutorial

The separation and analysis of chiral compounds is an important topic in various fields such as research, pharmaceutical industry, food control, agrochemistry, biochemistry, forensics and toxicology, etc. The interest in the mentioned fields is mainly due to the fact that enantiomers could react with the chiral environment. Therefore, their separation and analysis are a challenging issue because the use of these compounds can be related to humans and animals’ lives as well as to the environment (e.g., soil and water). Their separation can be performed with different analytical techniques such as high-performance liquid chromatography, gas chromatography, supercritical fluid chromatography, and microfluidic technique (capillary electrophoresis and capillary electrochromatography-CEC). Usually the direct resolution method is applied making use of a chiral stationary phase (CSP). This tutorial is aimed at illustrating the main features of CEC using a packed capillary, e.g., employing a silica-vancomycin CSP. The synthesis of the CSP, the instrumentation of CEC coupled with UV and mass spectrometry detectors, method optimization, and two selected applications are presented and discussed.

An automated and high-throughput data processing workflow for PFAS identification in biota by direct infusion ultra-high resolution mass spectrometry

The increasing recognition of the health impacts from human exposure to per- and polyfluorinated alkyl substances (PFAS) has surged the need for sophisticated analytical techniques and advanced data analyses, especially for assessing exposure by food of animal origin. Despite the existence of nearly 15,000 PFAS listed in the CompTox chemicals dashboard by the US Environmental Protection Agency, conventional monitoring and suspect screening methods often fall short, covering only a fraction of these substances. This study introduces an innovative automated data processing workflow, named PFlow, for identifying PFAS in environmental samples using direct infusion Fourier transform ion cyclotron resonance mass spectrometry (DI-FT-ICR MS). PFlow’s validation on a bream liver sample, representative of low-concentration biota, involves data pre-processing, annotation of PFAS based on their precursor masses, and verification through isotopologues. Notably, PFlow annotated 17 PFAS absent in the comprehensive targeted approach and tentatively identified an additional 53 compounds, thereby demonstrating its efficiency in enhancing PFAS detection coverage. From an initial dataset of 30,332 distinct m/z values, PFlow thoroughly narrowed down the candidates to 84 potential PFAS compounds, utilizing precise mass measurements and chemical logic criteria, underscoring its potential in advancing our understanding of PFAS prevalence and of human exposure.Graphical abstract

Crystallization resolution of racemic compounds via chiral surfactant

As one of the basic attributes of nature and the universe, chirality is valuable in biology, medicine, and materials science. However, enantiomer resolution remains a long-standing challenge. Herein, a novel surfactant for resolution of racemic compound with high performance has been outlined. Firstly, we synthesized a chiral surfactant and its chiral recognition ability to L-Alanine molecules was confirmed. Subsequently, the solid–liquid equilibrium curves were used to design the resolution route. The synthesized surfactant was further utilized to intensify the crystallization process of the racemic compound, resulting in a remarkable increase of L-Alanine products’ ee values from 0% to 99%. Finally, quantum chemical calculations and molecular dynamics simulations were employed to uncover the stereoselectivity recognition mechanism of surfactant to L-Alanine molecules. Overall, we propose a new idea for direct crystallization resolution of racemic Alanine by chiral surfactants that differs from the “rule of reversal”, which is highly attractive for chiral resolution.

Domain Decomposition and Model Order Reduction for Electromagnetic Field Simulations in Carbon Fiber Composite Materials

The computation of the electric field in composite materials at the microscopic scale results in an immense number of degrees of freedom. Consequently, this often leads to prohibitively long computation times and extensive memory requirements, making direct computation impractical. In this study, one employs an innovative approach that integrates domain decomposition and model order reduction to retain local information while significantly reducing computation time. Domain decomposition allows for the division of the computational domain into smaller, more manageable subdomains, enabling parallel processing and reducing the overall complexity of the problem. Model order reduction further enhances this by approximating the solution in a lower-dimensional subspace, thereby minimising the number of unknown variables that need to be computed. Comparative analysis between the results obtained from the reduced model and those from direct resolution demonstrates that our method not only reduces computation time but also maintains accuracy. The new method effectively captures the essential characteristics of the electric field distribution in composite materials, ensuring that the local phenomena are accurately represented. This study provides a contribution to the field of computational electromagnetics by presenting a feasible solution to the challenges posed by the high computational demands of simulating composite materials at the microscopic scale. The proposed methodology offers a promising direction for future research and practical applications, enabling more efficient and accurate simulations of complex material systems.

Nanoscale morphology imaging for arbitrary surfaces by optical coherence tomography

The imaging of nanoscale morphology using optical methods on arbitrary surfaces poses challenges, particularly in the presence of large axial distances and irregular shapes. In this work, we introduce a novel nano-resolution imaging method along the longitudinal direction, utilizing optical coherence tomography (OCT) to measure arbitrary surface morphology comprehensively. Based on the sparsity of the primary profile, our approach allows the adjustment of parameters such as the asymmetric penalty function ϕ, the regularization parameters αi and a high-pass filter to accommodate the micro-structure of any arbitrary surface. Remarkably, our method achieves an exceptional spatial resolution of 3.04 nm. The technique has been validated by observing the surface morphology of spherical and aspherical lenses with nanometer resolution in the longitudinal direction. With the ability to detect impurities and scratches with a height of tens of nanometers, this method can be used to study the fine structure of complex surfaces. This makes it an ideal choice for experimental requirements demanding high-resolution imaging and a broad en-face perspective.

Elevation Resolution Enhancement Oriented 3D Ultrasound Imaging.

Three-dimensional (3D) ultrasound imaging can be accomplished by reconstructing a sequence of two-dimensional (2D) ultrasound images. However, 2D ultrasound images usually suffer from low resolution in the elevation direction, thereby impacting the accuracy of 3D reconstructed results. The lateral resolution of 2D ultrasound is known to significantly exceed the elevation resolution. By combining scanning sequences acquired from orthogonal directions, the effects of poor elevation resolution can be mitigated through a composite reconstructing process. Moreover, capturing ultrasound images from multiple perspectives necessitates a precise probe positioning method with a wide angle of coverage. Optical tracking is popularly used for probe positioning for its high accuracy and environment-robustness. In this paper, a novel large-angle accurate optical positioning method is used for enhancing resolution in 3D ultrasound imaging through orthogonal-view scanning and composite reconstruction. Experiments on two phantoms proved that our method could significantly improve reconstruction accuracy in the elevation direction of the probe compared with single-angle parallel scanning. The results indicate that our method holds the potential to improve current 3D ultrasound imaging techniques.

Green HPLC Enantioseparation of Chemopreventive Chiral Isothiocyanates Homologs on an Immobilized Chiral Stationary Phase Based on Amylose tris-[(S)-α-Methylbenzylcarbamate

Sulforaphane is a chiral phytochemical with chemopreventive properties. The presence of a stereogenic sulfur atom is responsible for the chirality of the natural isothiocyanate. The key role of sulfur chirality in biological activity is underscored by studies of the efficacy of individual enantiomers as chemoprotective agents. The predominant native (R) enantiomer is active, whereas the (S) antipode is inactive or has little or no biological activity. Here we provide an enantioselective high-performance liquid chromatography (HPLC) protocol for the direct and complete resolution of sulforaphane and its chiral natural homologs with different aliphatic chain lengths between the sulfinyl sulfur and isothiocyanate group, namely iberin, alyssin, and hesperin. The chromatographic separations were carried out on the immobilized-type CHIRALPAK IH-3 chiral stationary phase with amylose tris-[(S)-methylbenzylcarbamate] as a chiral selector. The effects of different mobile phases consisting of pure alcoholic solvents and hydroalcoholic mixtures on enantiomer retention and enantioselectivity were carefully investigated. Simple and environmentally friendly enantioselective conditions for the resolution of all chiral ITCs were found. In particular, pure ethanol and highly aqueous mobile phases gave excellent enantioseparations. The retention factors of the enantiomers were recorded as the water content in the aqueous-organic modifier (methanol, ethanol, or acetonitrile) mobile phases progressively varied. U-shaped retention maps were generated, indicating a dual and competitive hydrophilic interaction liquid chromatography (HILIC) and reversed-phase liquid chromatography retention mechanism on the CHIRALPAK IH-3 chiral stationary phase. Finally, experimental chiroptical studies performed in ethanol solution showed that the (R) enantiomers were eluted before the (S) counterpart under all eluent conditions investigated.

The hustle is real: an examination of the self-related consequences of consuming idealized self-promotional content on LinkedIn

PurposeEveryday users of professional networks such as LinkedIn are flooded by posts presenting the achievements of their connections (e.g. I got a new job/award). The present research takes a self-discrepancy perspective to examine the mixed-emotional and behavioral consequences of viewing such idealized self-promotional content on professional networks.Design/methodology/approachThe emotional and behavioral consequences following viewership of idealized self-promotional content on LinkedIn are explored through one pilot study (N = 109) and one online experiment (N = 714), which is evaluated using structural equation modeling.FindingsViewership of idealized self-promotional content on professional social networking sites acts as an emotional double-edged sword for LinkedIn users. Users feel both dejection and symhedonia (i.e. happiness for others), dependent on their reported career-based self-discrepancy. We find the experience of symhedonia to be bound by the relational closeness of the poster (acquaintance vs close friend). Furthermore, we show how resultant emotions drive self-regulatory compensatory IT-use behaviors (i.e. direct resolution, fluid compensation, dissociation, and escapism).Originality/valueWe offer four distinct contributions. Firstly, we disentangle inconsistent findings of mixed emotions by introducing symhedonia to IT literature. Secondly, we investigate the boundary condition of relational closeness. Thirdly, we extend our findings by investigating compensatory-consumption behaviors that stem from mixed-affective outcomes. Finally, we do so in the context of professional networks, which are greatly understudied and are distinctive from personal networks. Practical implications are discussed.

In situ measurements and simulations of a net cage in currents

Accurate predictions of net cages’ deformation under current loads are vitally important for the welfare of stocked fish and the safety of cage structures. In this study, a scaled cage model was deployed at a fish farm. The incoming flow profile was measured through an Acoustic Doppler Current Profiler (ADCP) with high resolution in the depth direction, and the flow inside the cage was measured through an Acoustic Doppler Vector (ADV). Pressure tags were applied to capture the lifting of the cage under varying current conditions. The incoming flow velocity shows a good correlation with the lifting of the cage, and in general the rate of the cage being lifted by the flow increases with flow speed. However, the flow speed measured inside the cage is much less correlated to the upstream flow and cage deformation. Numerical cage models consisting of truss elements were developed; two flow reduction factors r = 0.9 and 0.8 derived from empirical formulas and measurements inside cages in previous studies were applied. The numerical model with r = 0.8 can predict the cage deformation well, with most relative deviations in the depth directions being less than 15%. The study indicates the feasibility of applying pressure tags with high precision to estimate current-induced cage deformation in situ, especially when a cage is experiencing obvious deformation.

Chiral Hydroxy Metabolite of Mebendazole: Analytical and Semi-Preparative High-Performance Liquid Chromatography Resolution and Chiroptical Properties.

Mebendazole (MBZ) is a benzimidazole carbamate anthelmintic used worldwide for the treatment and prevention of parasitic disorders in animals and humans. A large number of in vivo and in vitro studies have demonstrated that MBZ also has anticancer activity in multiple types of cancers. After oral administration, the phenylketone moiety of MBZ is rapidly reduced to the hydroxyl group to form the chiral hydroxy metabolite (MBZ-OH). To the best of our knowledge, there is no information in the literature on the stereochemical course of transformation and the anthelmintic and antitumor activity of individual enantiomers of MBZ-OH. In the present study, we describe in detail the direct HPLC resolution of MBZ-OH on a 100 mm × 4.6 mm Chirapak IG-3 column packed with 3 μm silica particles containing amylose (3-chloro-5-methylphenylcarbamate) as a selector. At 25 °C and using pure methanol as the mobile phase, the enantioseparation and resolution factors were 2.38 and 6.13, respectively. These conditions were scaled up at a semi-preparative scale using a 250 mm × 10 mm Chiralpak IG column to isolate multi-milligram amounts of both enantiomeric forms of the chiral metabolite. The chiroptical properties of the collected enantiomers were determined and, through a theoretical study, were related to the more stable conformations of MBZ-OH. The first and second eluted enantiomers were dextrorotatory and levorotatory, respectively, in dimethylformamide solution. Finally, by recording the retention factors of the enantiomers as the water content in the water-acetonitrile mobile phases was progressively varied, U-shaped retention maps were generated, indicating a dual and competitive hydrophilic interaction liquid chromatography and reversed-phase liquid chromatography retention mechanism on the Chirapak IG-3 chiral stationary phase.

The Relationships among Solar Flare Impulsiveness, Energy Release, and Ribbon Development

We develop the impulsiveness index, a new classification system for solar flares using the Solar Dynamics Observatory/Extreme Ultraviolet Experiment 304 Å Sun-as-a-star light curves. Impulsiveness classifies events based on the duration and intensity of the initial high-energy deposition of energy into the chromosphere. In stellar flare U-band light curves, Kowalski et al. found that impulsiveness is related to quantities such as a proxy for the Balmer jump ratio. However, the lack of direct spatial resolution in stellar flares limits our ability to explain this phenomenon. We calculate impulsiveness for 1368 solar flares between 2010 April and 2014 May. We divide events into categories of low, mid, and high impulsiveness. We find, in a sample of 480 flares, that events with high maximum reconnection rate tend to also have high impulsiveness. For six case studies, we compare impulsiveness to magnetic shear, ribbon evolution, and energy release. We find that the end of the 304 Å light-curve rise phase in these case studies corresponds to the cessation of polarity inversion line (PIL)-parallel ribbon motion, while PIL-perpendicular motion persists afterward in most cases. The measured guide-field ratio for low- and mid-impulsiveness case-study flares decreases about an order of magnitude during the impulsive flare phase. Finally, we find that, in four of the six case studies, flares with higher, more persistent shear tend to have low impulsiveness. Our study suggests that impulsiveness may be related to other properties of the impulsive phase, though more work is needed to verify this relationship and apply our findings to stellar flare physics.