Wetting of cellulose by different liquids is interesting from the point of view of the processing of cellulose-based nanomaterials. Here, the contact angles formed by water and several organic ...liquids on both native and acetylated cellulose were calculated from molecular dynamics simulations. It was found that liquid surface tension was crucial for their wetting behavior. Acetylation decreases the work of adhesion to most liquids investigated, even non-polar ones, while others are not affected. Water has the highest affinity to cellulose, both native and acetylated. The results have implications for liquid infiltration of nanocellulose networks and the interaction of cellulose with different liquids in general.
Experimental studies have shown that changes in stoichiometry (
R
, ratio of amine groups to epoxy groups) cause considerable variations in the properties of epoxy-amine systems. Rationales based on ...free volume concepts have been routinely used to address these variations in properties but have hardly been satisfactorily substantiated. Many of these rationales remain as unverified conjectures to date. Substantiating these rationales will certainly bolster our understanding of the structure-stoichiometry-property relationship, but is difficult, due to inherent challenges involved in unambiguously characterizing the structural heterogeneities induced by changes in stoichiometry (structural heterogeneities include compositional distribution in the functionality of monomers, non-uniform dispersion of elastic chains and topological defects). The aim of the present work is to gain molecular-level insights into this relationship and to verify the rationales that rely on free volume concepts used for addressing the variations in properties with stoichiometry, with the help of all-atom molecular dynamics (MD) simulations. Five epoxy-amine systems with varying
R
ranging from 0.4 to 3, including the stoichiometric system (
R
= 1), were considered for these purposes. The properties of interest namely density, glass transition temperature (
T
g
) and thermal expansion coefficient in the rubbery state (
α
rl
) of these systems were predicted. The local structure, fractional free volume and segmental mobility of these systems were then subsequently characterized as a function of stoichiometry and the results were analysed in detail. The role played by defects in properties and fractional free volume was then investigated. The results revealed significant insights into the compositional distribution of monomers with different functionalities as well as offered insights into the dispersion state and mobility of dangling chains, sols and elastic chains in the systems. Further, strong correlations were found between defect composition, fractional free volume at an elevated temperature (600 K) and thermomechanical properties (
T
g
and
α
rl
) and it was established that the key mechanism underlying these correlations was the plasticization caused by defects. Analysis based on the rule of mixture models showed that these correlations were found to be in good agreement with the interpretations based on free volume concepts. The results also revealed a strong negative correlation between fractional free volume at room temperature and defect composition, a phenomenon typically associated with the antiplasticization effect.
Perturbations in stoichiometry invariably induce topological defects in epoxy-amine systems which consequently affect properties. The present work elucidates the role played by topological defects on variations in properties with stoichiometry.
Purpose
After antral pulmonary vein isolation (PVI), electrical potentials may persist deep in the right superior pulmonary vein (RSPV). Whether these potentials signify true pulmonary vein potential ...(PVP) (implying inadequate RSPV isolation) or are far-field potentials (FFP) from the superior vena cava (SVC) is unclear. Here, we attempt to assess the incidence of persistent potentials in RSPV post-isolation and methods to differentiate PVP from FFP.
Methods
Following PVI, we mapped the RSPV and the SVC with simultaneously placed catheters. We recorded the incidence of SVC potentials, RSPV potentials, and distance between the 2 structures. When RSPV potentials were present, we assessed (1) relationship to SVC potentials, (2) RSPV-SVC distance, and (3) responses on pacing from either site.
Results
Among 43 consecutive post-PVI patients, 39 (91%) patients had SVC electrical activity but only 10 had persistent RSPV potentials. Of these, 2/10 had true PVP, and 8 were FFP from SVC. Bipolar electrogram morphology did not differentiate PVP from FFP, but low-amplitude (5 mA) SVC pacing was an effective maneuver. However, high-amplitude (≥ 10 mA) pacing from SVC and/or RSPV could result in far-field capture of the other site even when RSPV was devoid of electrical activity. Average RSPV-SVC distance was 15.9 mm.
Conclusions
Persistent RSPV potentials occur rarely post-PVI despite the close proximity to electrically active SVC. When present, true PVP can be differentiated from FFP by low-amplitude pacing from SVC. Bipolar EGM morphology and high-amplitude pacing are unreliable at differentiating these potentials.
Electrical stimulation therapies to promote bladder filling and prevent incontinence deliver continuous inhibitory stimulation, even during bladder emptying. However, continuous inhibitory ...stimulation that increases bladder capacity (BC) can reduce the efficiency of subsequent voiding (VE). Here we demonstrate that state-dependent stimulation, with different electrical stimulation parameters delivered during filling and emptying can increase both BC and VE relative to continuous stimulation in rats and cats of both sexes. We show that continuous 10 Hz pudendal nerve stimulation increased BC (120-180% of control) but decreased VE (12-71%, relative to control). In addition to increasing BC, state-dependent stimulation in both rats and cats increased VE (280-759% relative to continuous stimulation); motor bursting in cats increased VE beyond the control (no stimulation) condition (males: 323%; females: 161%). These results suggest that a bioelectronic bladder pacemaker can treat complex voiding disorders, including both incontinence and retention, which paradoxically are often present in the same individual.
Human-induced pluripotent stem cell cardiomyocytes (hiPSC-CMs) are a potential source to develop assays for predictive electrophysiological safety screening. Published studies show that the relevant ...physiology and pharmacology exist but does not show the translation between stem cell cardiomyocyte assays and other preclinical safety screening assays, which is crucial for drug discovery and safety scientists and the regulators. Our studies are the first to show the pharmacology of ion channel blockade and compare them with existing functional cardiac electrophysiology studies. Ten compounds (a mixture of pure hERG E-4031 and Cisapride, hERG and sodium Flecainide, Mexiletine, Quinidine, and Terfenadine, calcium channel blockers Nifedipine and Verapamil, and two proprietary compounds GSK A and B) were tested, and results from hiPSC-CMs studied on multielectrode arrays (MEA) were compared with other preclincial models and clinical drug concentrations and effects using integrated risk assessment plots. All ion channel blockers produced (1) functional effects on repolarization and depolarization around the IC25 and IC50 values and (2) excessive blockade of hERG and/or blockade of sodium current precipitated arrhythmias. Our MEA data show that hiPSC-CMs demonstrate relevant pharmacology and show excellent correlations to current functional cardiac electrophysiological studies. Based on these results, MEA assays using iPSC-CMs offer a reliable, cost effective, and surrogate to preclinical in vitro testing, in addition to the 3Rs (refine, reduce, and replace animals in research) benefit.
Ionic liquids (ILs) are thermally stable at both high and low temperatures, making them excellent solvents and electrolytes in extreme ambient conditions. In this work, we systematically studied the ...temperature effects on the various pathways of electrochemical reduction of CO2 in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimNTf2) and compared them with those in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BmpyNTf2) by electrochemical methods and density functional calculations. We summarize the crucial factors determining the reaction pathways for electroreduction of CO2 in EmimNTf2. Our results show that temperature can be used to modulate the reaction pathway of electrochemical reduction of carbon dioxide in this imidazolium-based IL via the effects on (i) the mass transport of the reactant and intermediates, (ii) the adsorption and solubility of the intermediates species, and (iii) the IL–electrode interface structure and properties.
Heart rhythm assessment is indispensable in diagnosis and management of many cardiac conditions and to study heart rate variability in healthy individuals. We present a proof-of-concept system for ...acquiring individual heart beats using smart speakers in a fully contact-free manner. Our algorithms transform the smart speaker into a short-range active sonar system and measure heart rate and inter-beat intervals (R-R intervals) for both regular and irregular rhythms. The smart speaker emits inaudible 18-22 kHz sound and receives echoes reflected from the human body that encode sub-mm displacements due to heart beats. We conducted a clinical study with both healthy participants and hospitalized cardiac patients with diverse structural and arrhythmic cardiac abnormalities including atrial fibrillation, flutter and congestive heart failure. Compared to electrocardiogram (ECG) data, our system computed R-R intervals for healthy participants with a median error of 28 ms over 12,280 heart beats and a correlation coefficient of 0.929. For hospitalized cardiac patients, the median error was 30 ms over 5639 heart beats with a correlation coefficient of 0.901. The increasing adoption of smart speakers in hospitals and homes may provide a means to realize the potential of our non-contact cardiac rhythm monitoring system for monitoring of contagious or quarantined patients, skin sensitive patients and in telemedicine settings.
Introduction
Late‐gadolinium enhancement magnetic resonance (LGE‐MRI) imaging is increasingly used in management of atrial fibrillation (AFib) patients. Here, we assess the usefulness of ...LGE‐MRI‐based fibrosis quantification to predict arrhythmia recurrence in patients undergoing cryoballoon ablation. Our secondary goal was to compare two widely used fibrosis quantification methods.
Methods
In 102 AF patients undergoing LGE‐MRI and cryoballoon ablation (mean age 62 years; 64% male; 59% paroxysmal AFib), atrial fibrosis was quantified using the pixel intensity histogram (PIH) and image intensity ratio (IIR) methods. PIH segmentations were completed by a third‐party provider as part of the standard of care at our hospital; Image intensity ratio (IIR) segmentations of the same scans were carried out in our lab using a commercially available software package. Fibrosis burdens and spatial distributions for the two methods were compared. Patients were followed prospectively for recurrent arrhythmia following ablation.
Results
Average PIH fibrosis was 15.6 ± 5.8% of the left atrial (LA) volume. Depending on threshold (IIRthr), the average IIR fibrosis (% of LA wall surface area) ranged from 5.0 ± 7.2% (IIRthr = 1.2) to 37.4 ± 10.9% (IIRthr = 0.97). An IIRthr of 1.03 demonstrated the greatest agreement between the methods, but spatial overlap of fibrotic areas delineated by the two methods was modest (Sorenson Dice coefficient: 0.49). Fourty‐two patients (41.2%) had recurrent arrhythmia. PIH fibrosis successfully predicted recurrence (HR 1.07; p = .02) over a follow‐up period of 362 ± 149 days; regardless of IIRthr, IIR fibrosis did not predict recurrence.
Conclusions
PIH‐based volumetric assessment of atrial fibrosis was modestly predictive of arrhythmia recurrence following cryoballoon ablation in this cohort. IIR‐based fibrosis was not predictive of recurrence for any of the IIRthr values tested, and the overlap in designated areas of fibrosis between the PIH and IIR methods was modest.
Caution must therefore be exercised when interpreting LA fibrosis from LGE‐MRI, since the values and spatial pattern are methodology‐dependent.
Direct-to-consumer (D2C) wearables are becoming increasingly popular in cardiovascular health management because of their affordability and capability to capture diverse health data. Wearables may ...enable continuous health care provider-patient partnerships and reduce the volume of episodic clinic-based care (thereby reducing health care costs). However, challenges arise from the unregulated use of these devices, including questionable data reliability, potential misinterpretation of information, unintended psychological impacts, and an influx of clinically nonactionable data that may overburden the health care system. Further, these technologies could exacerbate, rather than mitigate, health disparities. Experience with wearables in atrial fibrillation underscores these challenges. The prevalent use of D2C wearables necessitates a collaborative approach among stakeholders to ensure effective integration into cardiovascular care. Wearables are heralding innovative disease screening, diagnosis, and management paradigms, expanding therapeutic avenues, and anchoring personalized medicine.
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