Search

Vertically stacked van der Waals (vdW) heterostructures exhibit unique electronic, optical, and thermal properties that can be manipulated by twist-angle engineering. However, the weak phononic coupling at a bilayer interface imposes a fundamental thermal bottleneck for future two-dimensional devices. Using ultrafast electron diffraction, we directly investigated photoinduced nonequilibrium phonon dynamics in MoS2/WS2 at 4° twist angle and WSe2/MoSe2 heterobilayers with twist angles of 7°, 16°, and 25°. We identified an interlayer heat transfer channel with a characteristic timescale of ~20 picoseconds, about one order of magnitude faster than molecular dynamics simulations assuming initial intralayer thermalization. Atomistic calculations involving phonon-phonon scattering suggest that this process originates from the nonthermal phonon population following the initial interlayer charge transfer and scattering. Our findings present an avenue for thermal management in vdW heterostructures by tailoring nonequilibrium phonon populations.

Background: Atrial fibrillation (AF) is acknowledged as a disease continuum. Despite catheter ablation being recommended as a primary therapy for AF, the high recurrence rates have tempered the initial enthusiasm. Insulin resistance (IR) has been established as an independent predictor for the onset of AF. However, the correlation between non-insulin-based IR indices and late AF recurrence in patients undergoing radiofrequency catheter ablation remains unknown. Methods: A retrospective cohort of 910 AF patients who underwent radiofrequency catheter ablation was included in the analysis. The primary endpoint was late AF recurrence during the follow-up period after a defined blank period. The relationship between non-insulin-based IR indices and the primary endpoint was assessed using multivariate Cox hazards regression models and restricted cubic splines (RCS). Additionally, the net reclassification improvement and integrated discrimination improvement index were calculated to further evaluate the additional predictive value of the four IR indices beyond established risk factors for the primary outcome. Results: During a median follow-up period of 12.00 months, 189 patients (20.77%) experienced late AF recurrence, which was more prevalent among patients with higher levels of IR. The multivariate Cox hazards regression analysis revealed a significant association between these IR indices and late AF recurrence. Among the four indices, METS-IR provided the most significant incremental effect on the basic model for predicting late AF recurrence. Multivariable-adjusted RCS curves illustrated a nonlinear correlation between METS-IR and late AF recurrence. In subgroup analysis, METS-IR exhibited a significant correlation with late AF recurrence in patients with diabetes mellitus (HR: 1.697, 95% CI 1.397 − 2.063, P < 0.001). Conclusion: All the four non-insulin-based IR indices were significantly associated with late AF recurrence in patients undergoing radiofrequency catheter ablation. Addressing IR could potentially serve as a viable strategy for reducing the late AF recurrence rate. [ABSTRACT FROM AUTHOR]

Background: In this systematic review and meta‐analysis, we aimed to validate the predictive role of atrial fibrillation (AF) termination in long‐term arrhythmia recurrence. Method: Our search encompassed databases including MEDLINE, EMBASE, PubMed, and the Cochrane Library up to August 1, 2021. Three independent reviewers conducted screening and data extraction. The data included ablation strategy, recurrence mode, AF termination mode, numbers of patients, and recurrence cases in the termination and nontermination groups. The primary endpoint was the recurrence of atrial arrhythmia at long‐term follow‐up (≥ 12 months). Results: Our analysis included 22 publications, with 11 prospective studies being eligible for further meta‐analysis. Among these, 14 studies reported significantly lower rates of arrhythmia recurrence in the AF termination group compared to the nontermination group. Among seven studies involving 1114 patients that examined single procedure outcomes, the pooled estimated effect was RR 0.78 (95% CI 0.68–1.90) with an I2 value of 57%. Subgroup analysis focusing on termination mode as sinus rhythm yielded a pooled estimated effect of RR 0.74 (95% CI 0.59–0.92) with an I2 value of 47%. Additionally, analysis of seven studies involving 1433 patients for repeat procedures demonstrated a significant preference for the AF termination group (RR 0.83, 95% CI 0.71–0.97, I2 = 84%). Subgroup analysis indicated reduced heterogeneity when the termination mode was sinus rhythm (RR 0.68, 95% CI 0.51–0.90, I2 = 57%). Conclusion: Our study establishes that AF termination serves as an effective predictor for the success of persistent AF ablation procedures. This finding holds potential implications for clinical practice and contributes to our understanding of long‐term arrhythmia recurrence in the context of AF termination. [ABSTRACT FROM AUTHOR]

Background: There is limited available data regarding the impact of cycle length (CL) prolongation when converting atrial fibrillation (AF) to organized atrial tachycardia (AT) and its effect on clinical outcomes. Methods and Method: We retrospectively screened and included a cohort of 132 patients with persistent or long‐standing persistent AF who underwent circumferential pulmonary vein isolation (CPVI) and left atrial substrate modification (LASM) between January 2015 and October 2019. In all 132 consecutive patients, persistent AF was successfully converted into organized AT. For cases with recurrence after a 3‐month blanking period, a repeat procedure was conducted. Results: We observed a notable prolongation in CL after ablation (average increase of 56.6 ± 30 ms). Following a median follow‐up duration of 9.5 ± 5.1 months, 27 patients experienced recurrence. Through receiver operating curve (ROC) analysis, a prolonged CL cut‐off of 42.5 ms was identified, with a specificity of 71% and a sensitivity of 59.4%. Patients were categorized into two groups: those with CL less than 42.5 ms (group A, n = 48) and those with CL more than 42.5 ms (group B, n = 84). The Kaplan–Meier survival curves demonstrated a significantly higher recurrence‐free rate after catheter ablation in group B compared to group A (p = 0.002). Conclusions: Upon termination of persistent AF into AT during ablation, it was found that CL prolongation beyond 42.5 ms was associated with improved freedom from arrhythmia. [ABSTRACT FROM AUTHOR]

We present an experimental demonstration of ultrafast electron diffraction (UED) with THz-driven electron bunch compression and time-stamping that enables UED probes with improved temporal resolution. Through THz-driven longitudinal bunch compression, a compression factor of approximately four is achieved. Moreover, the time-of-arrival jitter between the compressed electron bunch and a pump laser pulse is suppressed by a factor of three. Simultaneously, the THz interaction imparts a transverse spatiotemporal correlation on the electron distribution, which we utilize to further enhance the precision of time-resolved UED measurements. We use this technique to probe single-crystal gold nanofilms and reveal transient oscillations in the THz near fields with a temporal resolution down to 50 fs. These oscillations were previously beyond reach in the absence of THz compression and time-stamping. [ABSTRACT FROM AUTHOR]

For many chemical reactions, it remains notoriously difficult to predict and experimentally determine the rates and branching ratios between different reaction channels. This is particularly the case for reactions involving short-lived intermediates, whose observation requires ultrafast methods. The UV photochemistry of bromoform (CHBr 3 ) is among the most intensely studied photoreactions. Yet, a detailed understanding of the chemical pathways leading to the production of atomic Br and molecular Br 2 fragments has proven challenging. In particular, the role of isomerization and/or roaming and their competition with direct C-Br bond scission has been a matter of continued debate. Here, gas-phase ultrafast megaelectronvolt electron diffraction (MeV-UED) is used to directly study structural dynamics in bromoform after single 267 nm photon excitation with femtosecond temporal resolution. The results show unambiguously that isomerization contributes significantly to the early stages of the UV photochemistry of bromoform. In addition to direct C-Br bond breaking within <200 fs, formation of iso-CHBr 3 (Br-CH-Br-Br) is observed on the same time scale and with an isomer lifetime of >1.1 ps. The branching ratio between direct dissociation and isomerization is determined to be 0.4 ± 0.2:0.6 ± 0.2, i.e., approximately 60% of molecules undergo isomerization within the first few hundred femtoseconds after UV excitation. The structure and time of formation of iso-CHBr 3 compare favorably with the results of an ab initio molecular dynamics simulation. The lifetime and interatomic distances of the isomer are consistent with the involvement of a roaming reaction mechanism.

Pulsed field ablation (PFA), a nonthermal ablative mechanism, has been proven to be effective and safe in clinical application. To date, PFA has been used for only atrial fibrillation (AF) ablation in limited clinical trials. The present study describes a case of paroxysmal AF in which mitral and cavotricuspid isthmus (CTI)-dependent atrial flutter was discovered incidentally during PFA operation and successfully ablated with PFA. This is the first medical record of PFA for AF combined with mitral and CTI atrial flutter. The present case report revealed that PFA can be independently used to treat complex arrhythmias, similar to radiofrequency (RF) ablation, without the need for assistance from other ablation methods. Concurrently, the present study, to the best of the authors' knowledge is the first to report a case using a point-to-point PFA ablation strategy for isthmus ablation. This highlights the potential of PFA in treating diverse arrhythmias across different regions, such as the mitral isthmus and other intricate areas, utilizing a point-to-point PFA ablation strategy., Competing Interests: The authors declare that they have no competing interests., (Copyright: © 2024 He et al.)