Cutoff Event Research Articles

Left atrial low-voltage areas, but not volume, predict the recurrence of atrial fibrillation in repeat ablation procedures

Abstract Background Left atrial (LA) low voltage areas (LVA) are a controversial target in atrial fibrillation ablation procedures. However, LVA and LA volume are good predictors of arrhythmia recurrence in ablation-naïve patients. Their predictive value in pre-ablated, myopathic atria is uncertain. Purpose Patient selection for repeat ablations is sometimes difficult. Predicting factors of rhythm outcome might help with the decision. Methods Consecutive patients with recurrent atrial fibrillation (AF) or atrial tachycardia (AT) scheduled for repeat LA ablation were included in the prospective Bernau ablation registry between 2016 and 2020. All patients received a complete LA ultra-high-density map before ablation. Maps were analyzed for LA size, LVA percentage and distribution. The predictive value of demographic, anatomic and mapping variables on AF recurrence was analyzed in univariate logistic regression and integrated in a multivariate Cox regression if the p-value was <0.250. Results 160 patients (50.6% male, 1.3 pre-ablations, 60% persistent AF) with complete LA voltage maps were included. Mean follow-up time was 16 ± 11 months. Mean recorded electrograms (EGMs) per map were 9754 ± 5808, mean LA volume was 176.1 ± 35.9 ml and mean rate of LVAs < 0.5 mV was 30.6% ± 23.1%. Baseline characteristics are depicted in table 1. During follow-up recurrence rate of AF or AT > 30 seconds was 55.6%. Patients with recurrence had a significant higher percentage of LVAs (40.0% vs. 18.8%, p<.001) but no relevant difference in LA volume (172 vs. 178 ml, p=.299). ROC curves revealed a cut-off of 22% LVAs with highest sensitivity (73.0%) and specificity (71.8%). Based on this cut-off event free survival was significantly higher in the Low LVA group (p<0.01), Figure 1. Other relevant clinical, anatomic or laboratory predictors could not be found in multivariate Cox regression analysis. Conclusion The amount of left atrial LVA is a good predictor for arrhythmia recurrence, even in a cohort of repeat ablations with progressively diseased atria. EAM derived left atrial volume has minor impact on recurrence in this group and should not solely guide the decision in favor or against further invasive treatment. Accomplishing a thorough 3D map of the left atrium to account for LVA should be mandatory in all repeat procedures.Baseline CharacteristicsKaplan-Meier for recurrence and voltage

High-resolution modeling of meander neck cutoffs: laboratory and field scales

Meandering rivers are distinguished by their characteristic sinuosity, which is subject to modulation through channel cutoff, resulting in the formation of oxbow lakes within the abandoned meander loops. Throughout the evolutionary course of a river, these cutoffs establish a connection between the channel and floodplain systems, both crucial to maintaining the dynamic equilibrium of the river system. Nonetheless, the interactive dynamic between the channel and floodplain and its influence on the transient behavior of the channel’s morphodynamics during a cutoff event are frequently reduced to simplistic representations in computational models. This study introduces a comprehensive numerical model that elucidates the adaptive processes of bed and planform during and subsequent to the inception of cutoff and oxbow lakes. The model is assessed through its application to a laboratory scale cutoff, before being employed to a real-world meandering river, specifically the Ucayali River in Peru, in order to gain understanding into channel development and the intricate patterns of planform dynamics following cutoff events. The model is able to capture the main modes of planform migration, translation and expansion for the case of the bend in the Ucayali River. During the neck cutoff, the model simulates the progression of erosional and depositional waves traveling in upstream and downstream directions respectively, underscoring the importance of incorporating both hydrodynamic and morphodynamic factors in characterizing the river dynamics associated with meander cutoffs.

Tsallis holographic dark energy model with event horizon cutoff in modified gravity

In this paper, we considered the Tsallis holographic dark energy model in frames of Nojiri–Odintsov gravity with [Formula: see text]. For IR, cutoff event horizon is taken. The cosmological evolution of such universe is investigated for various initial conditions and values of parameters. The dependence of the Hubble parameter [Formula: see text] from time in the future has an oscillation. It is shown that for [Formula: see text] appearance of singularities are typical and the time up to these singularities can be relatively small from cosmological viewpoint. The singularity is associated with the zero of second derivative of [Formula: see text] on [Formula: see text]. It is interesting to note that these models can describe observational data from Ia supernovae astrophysics and dependence of the Hubble parameter from redshift [Formula: see text] at least not worse than canonical [Formula: see text]CDM model.

PyRiverBed: A Python framework to generate synthetic riverbed topography for constant-width meandering rivers

Meandering is one of the unique processes in Earth surface dynamics. Since the 1960s, fluvial geomorphologists have generalized numerous widely-acknowledged empirical or semi-empirical formulae to describe meandering rivers' characteristics. The most frequently applied one is the Kinoshita high-sinuosity curve to describe meander channel planform geometry. Combining the Kinoshita curve with the Beck equations to describe the riverbed topography at equilibrium state, a prototype of a synthetic riverbed topography generating model is made for idealized meandering rivers. Such a method can be readily extended and applied to arbitrary meandering rivers in the real world, resulting in the synthetic riverbed topography model, pyRiverBed, presented herein. A meander migration and neck cutoff submodel is also embedded in pyRiverBed. Unlike existing linear and non-linear bend theory-based models, pyRiverbed aims towards generating the riverbed topography for each snapshot during the migration process. The present model can facilitate meandering river researchers to interpolate their field-measured bathymetric data using the synthetic bed, design their non-flat bed laboratory flumes for experiments, and initialize their hydrodynamic and morphodynamic numerical models. It can also provide guidance in stream restoration projects on designing a channel with a morphodynamic equilibrium bed. The quality of generated synthetic bed topography is evaluated through the comparison against both laboratory experiment data and field-measured data. The meander migration submodel is validated using a real-world channel migration and neck cutoff event. The validation results prove that the synthetic riverbed's accuracy is reasonably good, and the meander migration submodel can successfully predict meander migration and neck cutoff.

Regional Contamination History Revealed in Coal-Mining-Impacted Oxbow Lake Sediments

The aim of this study is to investigate complex pollution history and spatial trends of pollution (heavy metals and organic pollutants) in the selected oxbow lake (at the border between the Czech Republic and Poland) along the Odra River, located in the heavily polluted Ostrava urban agglomeration. Contaminant distribution is affected by position in the lake; the highest heavy metal concentrations were found in the central parts. Depth trends in 137Cs mass activity, hexachlorobenzene, and DDT metabolites were used as additional date levels. Depth profiles of heavy metals and their enrichment factors and multi-proxy stratigraphic analysis allowed two stages of oxbow lake evolution to be recognized. The initial stage was characterized by higher sediment accumulation rates in the whole oxbow lake, while during the second stage, sediment was deposited in a plug bar and in proximal parts of the lake, providing a more complete pollution record. Coal-rich layers were found in the deeper parts of the sedimentary record, related to coal mining activities. Samples rich in coal revealed a negative correlation with CIEL* (brightness) and conversely a positive correlation with specific biomarkers (homo hopanes and 16 α(H)-phyllocladane) and PAHs (secondary sorption to coal-rich strata). The sedimentary record since the oxbow lake cut-off event in 1966 showed a distinct vertical distribution of all pollutants. Maximum concentrations were attained during 1970s and 1980s, while a decreasing trend occurred after 1989 due to political and socio-economical changes in the former Czechoslovakia (now the Czech Republic).

A case study of a Kuroshio main path cut-off event and impacts on the South China Sea in fall-winter 2013–2014

This study examines a Kuroshio main path (KMP) cut-off event east of Taiwan Island occurred in fall-winter 2013–2014 and its impacts on the South China Sea (SCS) by analyzing satellite altimetry and mooring observations. Satellite altimeter sea level anomaly (SLA) images reveal a complete process that a huge cyclonic eddy (CE) from the Pacific collided with the Kuroshio and the western boundary from 15 October 2013 to 15 January 2014. Mooring observations evidenced that the Kuroshio upper ocean volume transport was cut off more than 82% from 17×106 m3/s in September to 3×106 m3/s in November 2013. The KMP cut-off event caused the Kuroshio branching and intruding into the SCS and strengthened the eddy kinetic energy in the northern SCS west of the Luzon Strait. Using the total momentum as a dynamic criterion to determine the role of eddy collision with the Kuroshio reasonably explains the KMP cut-off event.

Tidal meander migration and dynamics: A case study from the Venice Lagoon

Meandering patterns are universal features of tidal landscapes and exert a critical influence on the dynamics of tidal channel networks and on the stratigraphy of the intertidal platforms they dissect. Despite their importance in landscape evolution and their ubiquity, tidal meanders have received less attention when compared to their fluvial counterparts. To improve current understanding of tidal meander migration and its possible stratigraphic implications, we analysed a sequence of aerial photographs and satellite images (from 1938 to present) of a meandering tidal channel in the Venice Lagoon, which experienced multiple cutoff events during its evolution. Migration rates of the considered bends are in the range of 0.06–0.17 m/y, whereas migration rates per unit width vary between 0.6 and 2.5% yr−1. Detailed high-resolution geomorphological, sedimentological, and geochronological analyses were carried out for an abandoned meander bend, which experienced one of these cutoffs. Aerial photographs before and after the cutoff event (1938 and 1955, respectively) were used to infer a minimum velocity of migration (about 0.10 m/y). Sediment cores were also collected along a transect crossing through the meander neck in order to evaluate changes in grain size, sedimentation rates during the cutoff event, and gain further insight into the velocity of migration of meander bends. The spatial distribution of sedimentary facies (point-bar sand, oxbow lake, and salt-marsh mud), grain-size analyses, and 210 Pb and 137Cs chronologies highlighted that meander cutoff occurred progressively around 70 years before present with an average migration rate of 0.25 m/year. Such a procedure to estimate meander migration rates from stratigraphic data reveals to be particularly useful in the absence of high-temporal resolution remotely sensed-images. The effectiveness of the methods used and the high spatial and temporal resolution of the data call for further investigations and analyses of the type proposed herein, furthermore highlighting the potential of the study area as modern analogue for ancient tidal deposits.

Nanopatterning and tuning of optical taper antenna apex for tip-enhanced Raman scattering performance

This paper focuses on finding optimal electrochemical conditions from linear sweep voltammetry analysis for preparing highly reproducible tip-enhanced Raman scattering (TERS) conical gold tips with dc-pulsed voltage etching. Special attention is given to the reproducibility of tip apex shapes with different etchant mixtures. We show that the fractional Brownian motion model enables a mathematical description of the decaying current kinetics during the whole etching process up to the cutoff event. Further progress in preparation of highly reproducible smooth and sharp tip apexes is related to the effect of an additive, such as isopropanol, to aqueous acids. A finite-difference time-domain method based near-field analysis provides evidence that TERS performance depends critically on tip orientation relative to a highly focused laser beam. A TERS based criterion for recognizing gold tips able to couple/decouple optical near- and far-fields is proposed.

Testing the Role of Meander Cutoff in Promoting Gene Flow across a Riverine Barrier in Ground Skinks (Scincella lateralis)

Despite considerable attention, the long-term impact of rivers on species diversification remains uncertain. Meander loop cutoff (MLC) is one river phenomenon that may compromise a river’s diversifying effects by passively transferring organisms from one side of the river to the other. However, the ability of MLC to promote gene flow across rivers has not been demonstrated empirically. Here, we test several predictions of MLC-mediated gene flow in populations of North American ground skinks (Scincella lateralis) separated by a well-established riverine barrier, the Mississippi River: 1) individuals collected from within meander cutoffs should be more closely related to individuals across the river than on the same side, 2) individuals within meander cutoffs should contain more immigrants than individuals away from meander cutoffs, 3) immigration rates estimated across the river should be highest in the direction of the cutoff event, and 4) the distribution of alleles native to one side of the river should be better predicted by the historical rather than current path of the river. To test these predictions we sampled 13 microsatellite loci and mitochondrial DNA from ground skinks collected near three ancient meander loops. These predictions were generally supported by genetic data, although support was stronger for mtDNA than for microsatellite data. Partial support for genetic divergence of samples within ancient meander loops also provides evidence for the MLC hypothesis. Although a role for MLC-mediated gene flow was supported here for ground skinks, the transient nature of river channels and morphologies may limit the long-term importance of MLC in stemming population divergence across major rivers.

Long Term Evolution of "Benign" Multiple Sclerosis Patients in the London Ontario Database (P01.138)

Objective: Using conversion to secondary progressive (SP) multiple sclerosis (MS) as cutoff event for selecting patients with course, we tested which baseline features affects the probability of becoming no longer in the long term. Background Clinical severity of MS is extremely variable. Patients with not more than moderate disability within 10-15 years from onset are regarded as benign however, lack of consensus exists. Design/Methods: Among patients in the London Ontario database with course who had not experienced SP at 10 years from onset, binary logistic regression analysis assessed factors affecting the probability of remaining benign after 20 years. Results: Outcome at 20 years was known for 75% (n = 339/445) of those patients at 10 years from onset. Females predominated (71 %), mean age at onset was 26.8 years (S.D. 7.9) and most of patients had mono-symptomatic onset (71%) characterized by sensory disturbances (52.2%). Nearly half (166/339) had entered SP and were no longer benign. Eventually, among this subgroup 91.5% (152/166) reached DSS 6, 60.8% (101/166) DSS 8 and 16.8% (28/166) DSS 10 in 19.9, 31.2 and 49.7 mean years respectively. Female sex (OR = 1.68; p = 0.032) and younger age at disease onset (age 21-30 Vs > 30: OR = 1.77, p = 0.02; age ≤ 20 Vs > 30: OR = 3.36, p Conclusions: The onset of the SP phase is the watershed event differentiating cases. Lack of progression at 10 years from onset associated with about 50% probability of remaining 10 years later. Males and those older at disease onset had higher risk to become no longer benign. Supported by: Italian MS society. UK MS society. Disclosure: Dr. Scalfari has nothing to disclose. Dr. Neuhaus has nothing to disclose. Dr. Daumer has nothing to disclose. Dr. Muraro has nothing to disclose. Dr. Ebers has received personal compensation for activities with Bayer HealthCare Pharmaceuticals as a consultant.

The Role of Abandoned Channels as Refugia for Sustaining Pioneer Riparian Forest Ecosystems

In disturbance-prone ecosystems, organisms often persist in spatial refugia during stressful periods. A clear example is the colonization of abandoned river channels by pioneer riparian trees. Here, we examine the prominence of this establishment pathway for a foundation tree species (Fremont cottonwood, Populus fremontii) within the riparian corridor of a large river, the Sacramento River in central California. We quantified the total proportion of forest that initiated as a result of channel abandonment for a 160-km reach, analyzed concurrent patterns of tree establishment with floodplain accretion and sedimentation history, and developed a conceptual model of biogeomorphic evolution of abandoned channels. Historical air photo analysis indicated that stands associated with abandoned channels comprised more than 50% of the total extant cottonwood forest area. Tree-ring evidence showed that cottonwood stands commonly developed immediately following abandonment, and the recruitment window ranged from 4 to 40 years, but was less than 10 years at most sites. Rates of floodplain rise and fine sediment accumulation were high in young sites and decreased logarithmically over time. Together, these results suggest that abandoned channels are an important refuge for cottonwood recruitment, that the greatest opportunity for colonization occurs within a short period after the cutoff event, and that sedimentation processes influence the duration of the colonization window. On rivers where tree recruitment along the active channel is severely limited by hydrologic regulation and/or land management, abandoned channel refugia may play an even more important role in sustaining an ecologically functional riparian corridor. Preserving bank erosion, active meander corridors and forest regeneration zones created by cutoff events are therefore key conservation measures on shifting rivers.

ESR studies on polarons in long oligothiophenes

We have performed electron spin resonance (ESR) studies on long oligothiophenes (13 and 20 T) doped by iodine vapor. The oligomers gave anisotropic ESR spectra differing from ordinary cases in conjugated polymers. Our analyses by way of the Fourier transform of ESR spectra indicate that the cutoff event between parallel chains occurs at the same degree of frequency as the motion along a chain: 31.8 MHz at 50 K in 13 T. Above 150 K, we observed the signature of the cutoff motion between nonparallel chains (\ensuremath{\sim}5 MHz). We assert that polarons mainly move within aggregates consisting of parallel chains formed in the film.