Fast Pathway Research Articles

Ionic Hyperbranched Poly(amido-amine)-Incorporated Nanofiltration Membranes for High-Efficiency Dye Desalination.

High-efficiency dye desalination is crucial in the textile industry, considering its importance for human health, safe aquatic ecological systems, and resource recovery. In order to solve the problem of effective separation of univalent salt and ionic dye under the condition of high salt, ionic hyperbranched poly(amido-amine) (HBPs) were synthesized based on a simple and scalable one-step polycondensation method and then incorporated into the polyamide (PA) selective layers to construct charged nanochannels through interfacial polymerization (IP) on the surface of a polyvinyl chloride ultrafiltration (PVC-UF) hollow fiber membrane. Both the internal nanopores of HBPs (internal nanochannels) and the interfacial voids between HBPs and the PA matrix (external nanochannels) can be regarded as a fast water molecule transport pathway, while the terminal ionic groups of ionic HBPs endow the nanochannels with charge characteristics for improving ionic dye/salt selectivities. The permeate fluxes and dye/salt selectivities of HBP-TAC/PIP (57.3 L m-2 h-1 and rhodamine B (RB)/NaCl selectivity of 224.0) and HBP-PS/PIP (63.7 L m-2 h-1 and lemon yellow (LY)/NaCl selectivity of 664.0) membranes under 0.4 MPa operation pressure are much higher than PIP-only and HBP-NH2/PIP membranes. At the same time, this project also studied the membrane desalination process in a simulated high-salinity dye/salt mixture system to provide a theoretical basis and technical support for the actual dye desalination process.

Enhanced Low-Temperature Activity and Hydrothermal Stability of Ce-Mn Oxide-Modified Cu-SSZ-39 Catalysts for NH3-SCR of NOx

Cu-SSZ-39 zeolite with an AEI structure exhibits excellent hydrothermal stability and can be a potential alternative to Cu-SSZ-13 zeolite SCR catalysts for NOx removal in diesel vehicles. However, the inferior low-temperature performance of Cu-SSZ-39 leads to substantial NOx emissions during the cold-start period, impeding its practical application. In this study, Ce-Mn oxide-modified Cu-SSZ-39 catalysts (CeMnOx/Cu-SSZ-39) and references (CeO2/Cu-SSZ-39 and MnOx/Cu-SSZ-39) were prepared by the ion-exchange of Cu ions followed by impregnation of the oxide precursors, with the aim of enhancing the NH3-SCR performance at low temperatures. The modified catalysts exhibited improved low-temperature activity and hydrothermal stability compared to the unmodified counterpart. In particular, CeMnOx/Cu-SSZ-39 showed the highest activity among the three catalysts and achieved NOx conversions above 90% within the temperature range of 180 °C to 600 °C, even after undergoing hydrothermal aging at 800 °C. Experimental results indicated that the synergistic effect between Ce and Mn in CeMnOx improves the redox properties and acidity of the catalyst due to the presence of Ce3+, Mn4+, and abundant adsorbed oxygen species, which facilitate low-temperature SCR reactions. Furthermore, the interaction of CeMnOx with Cu-SSZ-39 stabilizes the zeolite framework and hinders the agglomeration of Cu species during the hydrothermal aging process, contributing to its exceptional hydrothermal stability. The kinetics and NO oxidation experiments demonstrated that CeMnOx provides access to fast SCR reaction pathways by oxidizing NO to NO2, resulting in a significant increase in low-temperature activity. This study provides novel guidelines for the design and preparation of Cu-SSZ-39 zeolite with outstanding SCR performance over a wide temperature range.

Selective efficient photocatalytic degradation of antibiotics and direct Z-type migration pathway for hierarchical core-shell TiO2/g-C3N4 composites.

Constructing superior Z-type photocatalytic heterojunction is beneficial to effectively enlarge interface contact, improve the photo-generated carrier separation rate, and retain the high redox ability. In this work, we designed a hierarchical core-shell g-C3N4/TiO2 structure to build Z-type heterojunction via combining simple template method and pyrolysis process. A close-knit Z-type heterojunction was constructed using TiO2 as a thick core and g-C3N4 as an ultra-thin shell. The effects of lamp source, wavelength, tetracycline (TC) concentration, and photocatalyst dose on the degradation performance on TC of g-C3N4/TiO2 were inspected. 0.1TiO2/g-C3N4 photocatalyst had the best degradation rate and highest removal rate within 30min, and its degradation rate was about 49, 23, and 5 times than pure g-C3N4, TiO2, and commercial TiO2/g-C3N4 in respect. Moreover, compared with degradation ability under Xenon lamp, LED irradiation for g-C3N4/TiO2composites showed aremarkable selectivedegradation. The fast and efficient Z-type transfer pathway of 0.1g-C3N4/TiO2 was realized by forming an optimized interface and abundant surface active sites ascribed to the combined action of thick TiO2 core and ultra-thin g-C3N4 shell. In addition, the degradation intermediates were analyzed by LC-MS and suggested pathways of degradation. The work could provide novel design concept to obtain reliable Z-type photocatalysts with hierarchical core-shell structure applied in degradation of antibioticwastewater.

Systematic observation-based diagnosis of atrioventricular nodal reentrant tachycardia with a bystander concealed nodoventricular pathway.

This study aimed to establish a systematic method for diagnosing atrioventricular nodal reentrant tachycardia (AVNRT) with a bystander concealed nodoventricular pathway (cNVP). We analyzed 13 cases of AVNRT with a bystander cNVP, 11 connected to the slow pathway (cNVP-SP) and two to the fast pathway (cNVP-FP), along with two cases of cNVP-related orthodromic reciprocating tachycardia (ORT). The diagnostic process was summarized in three steps. Step 1 was identification of the presence of an accessory pathway by resetting the tachycardia with delay (n = 9) and termination without atrial capture (n = 4) immediately after delivery of a His-refractory premature ventricular contraction (PVC). Step 2 was exclusion of ORT by atrio-His block during the tachycardia (n = 4), disappearance of the reset phenomenon after the early PVC (n = 7), or dissociation of His from the tachycardia during ventricular overdrive pacing (n = 1). Moreover, tachycardia reset/termination without the atrial capture (n = 2/2) 1 cycle after the His-refractory PVC was specifically diagnostic. Exceptionally, the disappearance of the reset phenomenon was also observed in the two cNVP-ORTs. Step 3 was verification of the AVN as the cNVP insertion site, evidenced by an atrial reset/block preceding the His reset/block in fast-slow AVNRT with a cNVP-SP and slow-fast AVNRT with a cNVP-FP or His reset preceding the atrial reset in slow-fast AVNRT with a cNVP-SP. AVNRT with a bystander cNVP can be diagnosed in the three steps with few exceptions. Notably, tachycardia reset/termination without atrial capture one cycle after delivery of a His-refractory PVC is specifically diagnostic.

Impact of rapid on-site evaluation in expediting the fast investigative lung cancer pathway.

EBUS-TBNA is a method of acquiring tissue samples from intrathoracic lymph nodes and central intrathoracic tumours in patients suspected of having lung cancer. Rapid on-site evaluation (ROSE) denotes assessing tissue samples during EBUS (or bronchoscopy), providing instant feedback on sample adequacy and provisional cytomorphological diagnosis. Sector multidisciplinary team (MDT) discussion can then make informed treatment decisions, with confirmatory immunohistochemistry being finalised before provision of final treatment. Currently, impact of ROSE on length of time patients spend on the lung cancer diagnostic pathway remains unclear. We retrospectively evaluated the impact of ROSE on the length of time between patients' EBUS/bronchoscopy procedures and discussion at sector MDT, referred to as time to treatment decision (TTD), at our institution. Additionally, we assessed impact of ROSE on number of passes (number of times nodes/masses were sampled) per procedure. The mean TTD was 77.9% shorter (p = 0.001) with ROSE present than when absent. Patients who received ROSE spend 34.3% less time (p = 0.028) on lung cancer diagnostic pathway overall. There was a significant reduction in number of passes in non-malignant nodes with ROSE present (2.23) than when absent (3.14) (p < 0.001). With ROSE present there was a significantly greater number of passes at malignant sites (5.07) than non-malignant sites (2.23) (p < 0.001). These findings support conclusions made in our institution's previous study, that utilisation of ROSE reduces TTD. ROSE also allows safe advancement through nodes with low suspicion of malignant involvement, focusing time on sampling nodes/masses of greater suspicion.

Co3O4 as an efficient passive NOx adsorber for emission control during cold-start of diesel engines

The Co3O4 nanoparticles, dominated by a catalytically active (110) lattice plane, were synthesized as a low-temperature NOx adsorbent to control the cold start emissions from vehicles. These nanoparticles boast a substantial quantity of active chemisorbed oxygen and lattice oxygen, which exhibited a NOx uptake capacity commensurate with Pd/SSZ-13 at 100 °C. The primary NOx release temperature falls within a temperature range of 200-350 °C, making it perfectly suitable for diesel engines. The characterization results demonstrate that chemisorbed oxygen facilitate nitro/nitrites intermediates formation, contributing to the NOx storage at 100 °C, while the nitrites begin to decompose within the 150-200 ºC range. Fortunately, lattice oxygen likely becomes involved in the activation of nitrites into more stable nitrate within this particular temperature range. The concurrent processes of nitrites decomposition and its conversion to nitrates results in a minimal NOx release between the temperatures of 150–200 °C. The nitrate formed via lattice oxygen mainly induces the NOx to be released as NO2 within a temperature range of 200–350 °C, which is advantageous in enhancing the NOx activity of downstream NH3-SCR catalysts, by boosting the fast SCR reaction pathway. Thanks to its low cost, considerable NOx absorption capacity, and optimal release temperature, Co3O4 demonstrates potential as an effective material for PNA applications.

Fast Energy Storage of SnS2 Anode Nanoconfined in Hollow Porous Carbon Nanofibers for Lithium-Ion Batteries.

The development of conversion-typed anodes with ultrafast chargingand large energy storage is quite challenging due to the sluggish ions/electrons transfer kinetics in bulk materials and fracture of the active materials. Herein, the design of porous carbon nanofibers/SnS2 composite (SnS2 @N-HPCNFs) for high-rate energy storage, where the ultrathin SnS2 nanosheets are nanoconfined in N-doped carbon nanofibers with tunable void spaces, is reported. The highly interconnected carbon nanofibers in three-dimensional (3D) architecture provide a fast electron transfer pathway and alleviate the volume expansion of SnS2 , while their hierarchical porous structure facilitates rapid ion diffusion. Specifically, the anode delivers a remarkable specific capacity of 1935.50mAhg-1 at 0.1C and excellent rate capability up to 30C with a specific capacity of 289.60mAhg-1 . Meanwhile, at a high rate of 20C, the electrode displays a high capacity retention of 84% after 3000 cycles and a long cycle life of 10000 cycles. This work provides a deep insight into the construction of electrodes with high ionic/electronic conductivity for fast-charging energy storage devices.

A novel dissolution-precipitation strategy to accelerate the sintering of yttrium oxide dispersion strengthened tungsten alloy with well-regulated structure

In this work, accelerated sintering of Y2O3 dispersion strengthened tungsten alloy with a well-regulated structure was achieved by a novel dissolution-precipitation strategy. As indicated, yttrium oxide was firstly dissolved into the lattices of W powder precursor during the thermal plasma synthesis process in a one-step and ultra-fast way, and then homogeneously precipitated out within W grains during sintering. The theoretical calculation reveals that the formation process of Y2O3 dispersoids enhanced the driving force of densification by increasing the sintering stress and declining the macroscopic viscosity, resulting in improved diffusion ability for the W skeleton. The microstructural investigation further confirmed the occurrence of mass inter-diffusion at the W-Y2O3 interface, which provides a fast diffusion pathway for W atoms, and is responsible for the accelerated densification kinetics. Being sintered at 1600 °C for 1 h, the as-obtained alloy possesses a high relative density of 98.26%, together with a refined grain size of 970 nm for W and 50 nm for intragranular Y2O3, respectively.

An assessment of different transition pathways to a green global economy

Transitioning to a green economy is urgently needed to achieve the climate targets by the end of this century. Here we investigate alternative pathways for the transition of the global economy from one dominated by the fossil-fueled (brown) sector to one dominated by the low-emission (green) sector. We modify a well-known integrated assessment model of climate change and economy to consider three transition pathways: Linear, Delayed, and Fast. Our results indicate that the main burden of the green transition lies on capital formation, accumulation, and transfers facilitated by full R&D investment in the green sector’s productivity. We also find that transition pathways rely on different mechanisms to achieve their targets. The Delayed pathway relies on the combination of higher green capital investment and an increase in green capital productivity through R&D investment, while the Fast pathway requires substantial transfers of capital from the brown sector coupled with high abatement efforts.

X3DFast model for classifying dairy cow behaviors based on a two-pathway architecture

Behavior is one of the important factors reflecting the health status of dairy cows, and when dairy cows encounter health problems, they exhibit different behavioral characteristics. Therefore, identifying dairy cow behavior not only helps in assessing their physiological health and disease treatment but also improves cow welfare, which is very important for the development of animal husbandry. The method of relying on human eyes to observe the behavior of dairy cows has problems such as high labor costs, high labor intensity, and high fatigue rates. Therefore, it is necessary to explore more effective technical means to identify cow behaviors more quickly and accurately and improve the intelligence level of dairy cow farming. Automatic recognition of dairy cow behavior has become a key technology for diagnosing dairy cow diseases, improving farm economic benefits and reducing animal elimination rates. Recently, deep learning for automated dairy cow behavior identification has become a research focus. However, in complex farming environments, dairy cow behaviors are characterized by multiscale features due to large scenes and long data collection distances. Traditional behavior recognition models cannot accurately recognize similar behavior features of dairy cows, such as those with similar visual characteristics, i.e., standing and walking. The behavior recognition method based on 3D convolution solves the problem of small visual feature differences in behavior recognition. However, due to the large number of model parameters, long inference time, and simple data background, it cannot meet the demand for real-time recognition of dairy cow behaviors in complex breeding environments. To address this, we developed an effective yet lightweight model for fast and accurate dairy cow behavior feature learning from video data. We focused on four common behaviors: standing, walking, lying, and mounting. We recorded videos of dairy cow behaviors at a dairy farm containing over one hundred cows using surveillance cameras. A robust model was built using a complex background dataset. We proposed a two-pathway X3DFast model based on spatiotemporal behavior features. The X3D and fast pathways were laterally connected to integrate spatial and temporal features. The X3D pathway extracted spatial features. The fast pathway with R(2 + 1)D convolution decomposed spatiotemporal features and transferred effective spatial features to the X3D pathway. An action model further enhanced X3D spatial modeling. Experiments showed that X3DFast achieved 98.49% top-1 accuracy, outperforming similar methods in identifying the four behaviors. The method we proposed can effectively identify similar dairy cow behaviors while improving inference speed, providing technical support for subsequent dairy cow behavior recognition and daily behavior statistics.

Pseudo-slow-fast atrioventricular nodal reentrant tachycardia: Is the fast pathway a criminal or innocent bystander?

The intracardiac electrograms are shown during scanned single premature ventricular extrastimuli with a decreasing coupling interval in a very short RP tachycardia. What is the diagnosis and is the fast pathway essential for sustaining the tachycardia?

Folding kinetics of an entangled protein.

The possibility of the protein backbone adopting lasso-like entangled motifs has attracted increasing attention. After discovering the surprising abundance of natively entangled protein domain structures, it was shown that misfolded entangled subpopulations might become thermosensitive or escape the homeostasis network just after translation. To investigate the role of entanglement in shaping folding kinetics, we introduce a novel indicator and analyze simulations of a coarse-grained, structure-based model for two small single-domain proteins. The model recapitulates the well-known two-state folding mechanism of a non-entangled SH3 domain. However, despite its small size, a natively entangled antifreeze RD1 protein displays a rich refolding behavior, populating two distinct kinetic intermediates: a short-lived, entangled, near-unfolded state and a longer-lived, non-entangled, near-native state. The former directs refolding along a fast pathway, whereas the latter is a kinetic trap, consistently with known experimental evidence of two different characteristic times. Upon trapping, the natively entangled loop folds without being threaded by the N-terminal residues. After trapping, the native entangled structure emerges by either backtracking to the unfolded state or threading through the already formed but not yet entangled loop. Along the fast pathway, trapping does not occur because the native contacts at the closure of the lasso-like loop fold after those involved in the N-terminal thread, confirming previous predictions. Despite this, entanglement may appear already in unfolded configurations. Remarkably, a longer-lived, near-native intermediate, with non-native entanglement properties, recalls what was observed in cotranslational folding.

Estrogen-induced phenotype in hiPSC-derived cardiomyocytes of a woman affected by both Long QT Syndrome Type 2 and Polycystic Ovary Syndrome

Abstract Introduction Long QT Syndrome (LQTS) is an arrhythmogenic disorder caused either by genetic alteration or by exogenous factors. Polycystic Ovary Syndrome (PCOS) is a disease associated with high levels of testosterone and low levels of estrogen (E2). It has been suggested that hormones can influence the occurrence of malignant cardiac events in LQTS type 2 (LQT2) women, carriers of mutations on the potassium channel (hERG). However, the precise mechanisms governing this process still need to be clarified. Purpose We studied a patient affected by both LQT2 and PCOS who started experiencing cardiac symptoms after initiation of hormonal replacement therapy. We observed a correlation with the occurrence of arrhythmic events and the irregular assumption of the hormonal replacement therapy, thus we aim to dissect the underlying mechanism in patient-in-a-dish cardiac cellular model. Methods Induced Pluripotent Stem Cells (hiPSC) were generated from a woman affected by both LQT2 and PCOS and from a healthy donor, and then differentiated into cardiomyocytes (hiPSC-CMs). hiPSC-CMs were stimulated with E2 10nM for five time points (1, 5, 10, 15 and 30 minutes). The expression of potassium channel hERG, and of the G-coupled estrogen receptor (GPER) regulating the fast non-genomic pathway, were quantified after E2 stimulation at different time points by In Cell Western (ICW). The Unstimulated sample were used to normalize GPER and hERG expression to 100%. Electrophysiological experiments were performed using the whole-cell patch-clamp technique in current-clamp mode to record spontaneous action potentials (APs). AP duration at 30%, 50% and 90% repolarization (APD30, APD50 and APD90) was quantified. During spontaneous activity, AP duration values were rate-corrected with Bazett’s formula, thus obtaining cAPD. Results LQT2 hiPSC-CMs express higher levels of GPER (p&amp;lt;0.05) and hERG (p&amp;lt;0.01) than healthy hiPSC-CMs. A significant decrease in GPER expression was detected during 10nM E2 stimulation in healthy cardiomyocytes at the five time points (p&amp;lt;0.0001), while any difference was detected in hERG expression levels. E2 stimulation at different time points did not affect neither GPER nor hERG expression in LQT2 hiPSC-CMs. In LQT2 hiPSC-CMs, APDC values were significantly increased (p&amp;lt;0.0001) compared to healthy cells; pre-incubation with E2 for 10 minutes significantly shortened cAPD50 and increased spontaneous firing rate. In healthy hiPSC-CMs, E2 had no effect. Conclusions The hiPSC-CM model reproduces the LQT2 clinical phenotype. cAPD50 shortening by E2 was unexpected based on the proarrhythmic effect in the patient. The mechanism of LQT2-specific effects of E2 are under investigation.

Abstract 13443: Dead Antegrade Fast Pathway: A Dilemma for Atrioventricular Nodal Re-Entry Tachycardia Ablation

Background: Catheter ablation is the first-line treatment option for symptomatic atrioventricular nodal re-entry tachycardia (AVNRT). Ablation of the slow pathway is preferred over the fast pathway in Typical AVNRT, given that it has a lower risk of heart block. Still, baseline conduction abnormalities and findings on the Electrophysiology (EP) study can alter the ablation strategy. Case: We report a case of a 61-year-old male who was referred to EP clinic for symptomatic suspected AVNRT. His baseline electrocardiogram (EKG) showed normal sinus rhythm with PR prolongation, right bundle branch block, and left anterior fascicular block. EP study was performed, which showed prolonged AH interval with normal HV interval (Figure 1). Typical AVNRT was induced with a premature atrial complex; there was no AV nodal jump before the tachycardia, but it had a long AH interval (Figure 2). There was no evidence of pre-excitation. Discussion: Since there was no antegrade conduction through the fast pathway, conventional slow pathway ablation was not viable as it would make the patient pacemaker (PM)-dependent. Even ablating the fast pathway, though not PM-dependent, would still put him at risk for complete heart block, especially when his antegrade conduction via the slow pathway was unreliable. Hence PM was discussed with the patient before ablation. The fast pathway was mapped and ablated (Figures 3, 4, and 5) without complication, and PM was implanted. Conclusion: This case emphasizes the role of fast pathway ablation in symptomatic AVNRT in patients with conduction abnormalities and the importance of EP study to see the need for PM post-ablation.

Abstract 12422: Does a Jump in the Atrioventricular Conduction Curve Really Indicate a Switch From Fast Pathway to Slow Pathway Conduction?

Introduction: A jump in the atrioventricular (AV) conduction curve (aka, a discontinuous curve) remains the current clinical criterion for diagnosing dual pathway AV nodal electrophysiology. However, it has never been proven that a jump in the AV conduction curve indicating a transition from fast pathway (FP) to slow pathway (SP) conduction, as it has been assumed. Hypothesis: A jump in the AV conduction curve may not reflect the transition from FP to SP conduction, as assumed it does by the current clinical criterion. Methods: Eighty-one experimental records from rabbit AV nodal preparations containing the following data were analyzed. 1. had at least one AV conduction curve, and 2. had intracellular action potential recordings from AV nodal fibers and/or recording of His electrogram alternans (a validated new index of dual pathway conduction). Results: There were 11 (13%) of 81 preparations showing a jump in the AV conduction curve. In these preparations, the transition from FP to SP conduction was smooth. The jumps always occurred after the FP to SP transition at a much shorter prematurity (Figure). On average, the FP-SP transition occurred at prematurity of 196±39ms versus the jump at 117±9ms (P&lt;0.001). Complex intranodal/nodal-atrial reentries were detected after the FP to SP transition. The jumps were always associated with and most likely caused by the intranodal/nodal-atrial reentry and its subsequent conduction to the His bundle, rather than a direct conduction by the premature beat itself. Conclusions: The transition from FP to SP conduction does not produce a jump in the AV conduction curve. A jump in the AV conduction curve is likely caused by induction of intranodal/nodal-atrial reentry by the premature beat and the subsequent conduction of the reentrant beat to the His bundle, rather than a direct conduction by the premature beat itself. Thus, a jump in the AV conduction curve as the current clinical criterion of dual pathway conduction should be invalidated.

LiCoO2 Cathode Modified With Liquid-exfoliated Graphene for High-performance Full Batteries

Graphene has been successfully applied for modification of LiCoO2 cathode, but finding a large-scale preparation method of high-quality graphene for commercial application remains a great challenge. In this work, we have demonstrated a facile strategy to prepare few-layer defect-free graphene. The prepared graphene performs well in application for LiCoO2 cathode in the full battery system as conductive additives. The superior conductive graphene is attached to LiCoO2 particles, and fast pathways of electronic transport in the bulk electrode and protective layer on the interface between LiCoO2 and electrolyte are constructed. The cathode with 0.35% wt% graphene displays superior rate capacity (145 mAh/g at 2C) and excellent 4.5 V high-voltage cycle performance, which can be contributed to lower internal resistance and a more stabilized interface. The graphene shows great potential in commercial applications for high-performance LiCoO2-based full batteries.

MXene: A two-dimensional nanomaterial for enhancing start-up performance of high temperature proton exchange membranes

Commercializing high temperature proton exchange membrane fuel cells (HT-PEMFCs) faces the challenge of slow start-up at low temperatures. Meanwhile, start-up under low relative humidity or anhydrous is beneficial for HT-PEMFCs, it can avoid lots of problems associated with water flooding. So, it requires membranes to have excellent water retention and fast proton transport pathways, which is the key to fast start-up. This study addresses this issue by incorporating MXene into membranes, achieving improved start-up and operating performance (144.1, 175.4, 225.6, 740.8 mW cm−2 at 40, 60, 80 and 160 °C under anhydrous, respectively). It attributes to MXene's excellent water retention and hydroxyl group (-OH). Through alkali treatment to add more –OH to MXene, improved proton conductivity proves that –OH has a positive affect on transporting proton. Further, by grafting sulfonic acid groups onto the MXene, start-up performance has enhanced at all temperatures (178.7, 200.0, and 280.8 mW cm−2 at 40, 60, and 80 °C under anhydrous, respectively), and power density of 160 °C was significantly improved compared to pristine membranes. The incorporation of sulfonic acid groups also led to better mechanical properties and oxidative stability of the composite membranes. MXene's potential for water retention, hydroxyl group, and modifiability – all desirable traits for accelerating start-up of HT-PEMs.

Slow magnetic relaxation behaviors and diamagnetic dilution studies of a carboxyl bridged dinuclear dysprosium(III) complex

By using a rigid bulky carboxylic ligand α-cyanocinnamic acid (CCA), a dinuclear dysprosium (III) complex [Dy2(CCA)6 (MeOH)4] (1) was synthesized. Single crystal X-ray crystallography reveals that the two eight-coordinate dysprosium ions are bridged by four deprotonated carboxyl groups, forming a centrosymmetric paddle-wheel-like structure. Dynamic magnetic property measurements indicate that complex 1 displays field-induced slow magnetic relaxation. The temperature-dependent relaxation times can be fitted using Orbach and Raman processes with parameters of n = 2.8 (2), C = 27 (8) s−1/Kn, τ0 = 5 (2) × 10−10 s and Ueff = 40 (3) cm−1. Magnetic studies on the diamagnetic YIII-diluted analogue [Dy0.206Y1.794(CCA)6 (MeOH)4] (2) reveal its slow magnetic relaxation behavior without external dc field and the antiferromagnetic coupling between the DyIII ions in 1. Fits on the obtained relaxation times of 2 lead to the parameters of n = 4.5 (3), C = 0.7 (2) s−1/Kn, τ0 = 2.8 (2) × 10−9 s and Ueff = 38 (2) cm−1. The results suggest that slow magnetic relaxation originates from the single-ion relaxation of DyIII ions. Moreover, the diamagnetic dilution can suppress other fast relaxation pathways at low temperature, on account of the elimination of magnetic coupling and dipolar interaction. Ab initio calculations were then performed on the single DyIII ion species {YDy} and indicate that the first excited Kramers doublets (KDs) lie at ca. 76 cm−1, which is slightly higher than the experimental Ueff value. The intramolecular magnetic interactions were also calculated and indicate a weak ferromagnetic dipole-diploe magnetic interaction and an antiferromagnetic exchange coupling.

Rational design of microflower-like manganese-doped ultrathin cobalt hydroxide nanosheets as bifunctional electrode materials for electrochemical sensing and supercapacitor applications

Noble metal-based electrocatalyst must be replaced for electrochemical applications by earth-rich, highly active, low-cost, and highly efficient dual-function electrocatalysts. In this study, transition metal-based hydroxides (TMHs), such as 2D manganese-doped cobalt hydroxide (Mn-Co(OH)2) ultrafine nanosheets, are investigated using a very simple large-scale co-precipitation method for efficient electrochemical sensing (nitrofurantoin (NFT)) and supercapacitor (SC) applications. The characterization results show that the porous and large surface area, polycrystalline nature, confinement of the 2D orientation, and strong synergistic effect contribute to the admirable electrochemical concert of Mn-Co(OH)2 for both sensing and SC applications. CV, GCD, EIS, and DPV techniques are used to thoroughly investigate electrochemical and physicochemical properties. As an electrochemical sensor, the Mn-Co(OH)2 modified disposable screen-printed carbon electrode (Mn-Co(OH)2/SPCE) shows excellent electrochemical assets for NFT detection with broad linear ranges (0.05–219 μM and 262–641 μM), low detection limit (0.012 μM) and good anti-interference ability. The obtained specific capacitance of Mn-Co(OH)2 is 348.8 F g−1 at 1 A g−1 with a maintenance capacitance of 80.76 % after 5000 cycles at 10 A g−1. The enhanced electrochemical behavior of Mn-Co(OH)2 may be related to the fast diffusion pathways of Mn doping and the enhanced redox reaction (cobalt ions) of the flower-like ultrathin nanosheets owing to their high surface area (214 m2/g). The characterization results and electrochemical performance (sensing and SCs) provide important and noteworthy insights into the synthesis of noble metal-free and high-efficiency transparent 2D TMHs nanosheets with high performance that can be widely used in various applications.

Research on Students’ Action Behavior Recognition Method Based on Classroom Time-Series Images

Students’ action behavior performance is an important part of classroom teaching evaluation. To detect the action behavior of students in classroom teaching videos, and based on the detection results, the action behavior sequence of individual students in the teaching time of knowledge points is obtained and analyzed. This paper proposes a method for recognizing students’ action behaviors based on classroom time-series images. First, we propose an improved Asynchronous Interaction Aggregation (AIA) network for student action behavior detection. By adding a Multi-scale Temporal Attention (MsTA) module and a Multi-scale Channel Spatial Attention (MsCSA) module to the fast pathway and slow pathway, respectively, the accuracy of student action behavior recognition is improved in SlowFast, which is the backbone network of the improved AIA network,. Second, the Equalized Focal Loss function is introduced to improve the category imbalance that exists in the student action behavior dataset. Experimental results on the student action behavior dataset show that the method proposed in this paper can detect different action behaviors of students in the classroom and has better detection performance compared to the original AIA network. Finally, based on the results of action behavior recognition, the seat number is used as the index to obtain the action behavior sequence of individual students during the teaching time of knowledge points and the performance of students in this period is analyzed.