心内膜微波逐点房颤消融术的温度场研究

根据实际临床需求,针对房颤微波消融中常见的逐点消融术,探究时间功率和天线距离对相邻2个消融点消融效果的影响,找出最佳的消融功率和最佳天线距离,为临床治疗提供参考.构建了包括血液、心肌、脂肪的3层模型,采用2.45 GHz频率进行了电磁热耦合计算并得到了心肌中温度的分布.功率采取30、40、50和60 W,2个消融点之间的距离采取0.5、1、1.5和2 cm.结果表明:功率为30 W和40 W时会导致消融区域比较小;功率为60 W时会导致最高温度过高且消融的范围与功率为50 W的时候相比并没有显著的提升;相邻2个消融点间距为0.5cm和1 cm时会导致总消融区域比较小且最高温度过高;间距为2 cm时无法形成连续透壁的消融区域.因此50 W是最佳消融功率,1.5 cm是最佳消融2点间距,可以在保证最高温度不过高、连续透壁的情况下,获得比较大的总消融区域和较高的能量利用效率.在50 W、1.5 cm的最佳消融方案下,逐点消融2个点所需要的总消融时间为43.2 s,最高温度为87.2℃,连续透壁消融长度、心肌内部最大消融长度及最大消融宽度分别为2.486、2.770、1.865 cm.     

Robust genetic programming‐based detection of atrial fibrillation using RR intervals

In this study, two variants of genetic programming, namely linear genetic programming (LGP) and multi‐expression programming (MEP) are utilized to detect atrial fibrillation (AF) episodes. LGP‐ and MEP‐based models are derived to classify samples of AF and Normal episodes based on the analysis of RR interval signals. A weighted least‐squares (WLS) regression analysis is performed using the same features and data sets to benchmark the models. Another important contribution of this paper is identification of the effective time domain features of heart rate variability (HRV) signals upon an improved forward floating selection (IFFS) analysis. The models are developed using MIT‐BIH arrhythmia database. The diagnostic performances of the LGP and MEP classifiers are evaluated through receiver operating characteristics (ROC) analysis. The results indicate that the LGP and MEP models are able to diagnose the AF arrhythmia with an acceptable high accuracy. The proposed models have significantly better diagnosis performances than the regression and several models found in the literature.     

Feature selection using support vector machines and bootstrap methods for ventricular fibrillation detection

Early detection of ventricular fibrillation (VF) is crucial for the success of the defibrillation therapy in automatic devices. A high number of detectors have been proposed based on temporal, spectral, and time-frequency parameters extracted from the surface electrocardiogram (ECG), showing always a limited performance. The combination ECG parameters on different domain (time, frequency, and time-frequency) using machine learning algorithms has been used to improve detection efficiency. However, the potential utilization of a wide number of parameters benefiting machine learning schemes has raised the need of efficient feature selection (FS) procedures. In this study, we propose a novel FS algorithm based on support vector machines (SVM) classifiers and bootstrap resampling (BR) techniques. We define a backward FS procedure that relies on evaluating changes in SVM performance when removing features from the input space. This evaluation is achieved according to a nonparametric statistic based on BR. After simulation studies, we benchmark the performance of our FS algorithm in AHA and MIT-BIH ECG databases. Our results show that the proposed FS algorithm outperforms the recursive feature elimination method in synthetic examples, and that the VF detector performance improves with the reduced feature set.     

Anti‐thrombotic therapy for atrial fibrillation in patients with chronic kidney disease: Current views

Chronic kidney disease (CKD) occurs in approximately one‐third of patients with non‐valvular atrial fibrillation (AF). The presence of CKD, particularly advanced CKD, confers increased risk of both thromboembolism and major bleeding in this group of patients who are already at risk for ischemic stroke and systemic embolism and at risk of bleeding due to anticoagulation. Studies assessing the effect of warfarin on risk of ischemic stroke, systemic embolism, and major bleeding have produced disparate results, particularly in patients with advanced CKD including those treated with hemodialysis. The direct oral anticoagulants (DOAC's) have been studied in patients with stage III (moderate) CKD and appear to be as effective or more effective (dabigatran 150 mg twice daily) than warfarin in preventing ischemic stroke or embolism in this group. Two of the DOAC's, apixaban and edoxaban, confer lower risk of major bleeding than warfarin with appropriate dose adjustments. Substantial gaps exist in our knowledge of anti‐thrombotic therapy in patients with AF and CKD, primarily due to exclusion of patients with advanced CKD from randomized controlled trials comparing DOAC's with warfarin.     

Enzyme-Activatable Polypeptide for Plasma Membrane Disruption and Antitumor Immunity Elicitation

Enzyme-instructed self-assembly of bioactive molecules into nanobundles inside cells is conceived to potentially disrupt plasma membrane and subcellular structure. Herein, an alkaline phosphatase (ALP)-activatable hybrid of ICG-CF₄KY^p is facilely synthesized by conjugating photosensitizer indocyanine green (ICG) with CF₄KY^p peptide via classical Michael addition reaction. ALP-induced dephosphorylation of ICG-CF₄KY^p enables its transformation from small-molecule precursor into rigid nanofibrils, and such fibrillation in situ causes severe mechanical disruption of cytomembrane. Besides, ICG-mediated photosensitization causes additional oxidative damage of plasma membrane by lipid peroxidation. Hollow MnO₂ nanospheres devote to deliver ICG-CF₄KY^p into tumorous tissue through tumor-specific acidity/glutathione-triggered degradation of MnO₂, which is monitored by fluorescent probing and magnetic resonance imaging. The burst release of damage-associated molecular patterns and other tumor antigens during therapy effectively triggers immunogenetic cell death and improves immune stimulatory, as demonstrated by the promotion of dendritic cell maturation and CD8⁺ lymphocyte infiltration, as well as constraint of regulatory T cell population. Taken together, such cytomembrane injury strategy based on peptide fibrillation in situ holds high clinical promise for lesion-specific elimination of primary, abscopal, and metastatic tumors, which may enlighten more bioinspired nanoplatforms for anticancer theranostics.     

增容作用对PET在PP中原位成纤及增强效果的影响

以接枝极性官能团的聚丙烯为增容剂,在保持一定拉伸比的条件下,与聚丙烯(PP)和聚对苯二甲酸乙二醇酯(PET)共混挤出。通过改变增容剂的用量,控制PET在PP中的形态结构。当增容剂含量为3%时,PET以纤维状分散在基体PP中,达到了较好的增强效果。     

面向房颤分析的左心房分割方法综述

房颤是一种起源于心房的心脏疾病。据估计全球有超过3 000万人受其影响,虽然通过治疗可以降低患病风险,但房颤通常是隐匿的,很难及时诊断和干预。房颤的诊断方法主要有心脏触诊、光学体积描记术、血压监测振动法、心电图和基于影像的方法。房颤类型主要为阵发性房颤,前4种诊断方法不一定能捕捉到房颤发作,而且诊断周期长、成本高、准确率低及容易受医生的影响。左心房的解剖结构为房颤病理和研究进展提供了重要信息,基于医学影像的房颤分析需要准确分割左心房,通过分割结果计算房颤的临床指标,例如,射血分数、左心房体积、左心房应变及应变率,然后对左心房功能进行定量评估。采用影像的方法得出的诊断结果不易受人为干扰且具有处理大批量患者数据的能力,辅助医生及早发现房颤,对患者进行干预治疗,提高对房颤症状和临床诊断的认识,在临床实践中具有重大意义。本文将已有的分割方法归纳为传统方法、基于深度学习的方法以及传统与深度学习结合的方法。这些方法得到的结果为后续房颤分析提供了依据,但目前的分割方法许多都是半自动的,分割结果不够精确,训练数据集较小且依赖手工标注。本文总结了各种方法的优缺点,归纳了目前已有的公开数据集和房颤分析的临床应用,并展望了未来的发展趋势。     

Human Serum Transferrin Fibrils: Nanomineralisation in Bacteria and Destruction of Red Blood Cells

Fibrils formed by human serum transferrin [(1–3 μM ) apo‐Tf, partially iron‐saturated (Fe_0.6‐Tf) and holo‐Tf (Fe₂‐Tf) forms], from dilute bicarbonate solutions, were deposited on formvar surfaces and studied by electron microscopy. We observed that possible bacterial contamination appears to give rise to long, pea‐pod‐like (PPL) structures for Fe₂‐Tf, attributable to the formation of polyhydroxybutyrate (PHB) storage granules, under the nutrient‐limiting conditions used. These PPL structures contained periodic nanomineralisation sites susceptible to uranyl stain. Extended incubation of transferrin solutions (about four days) gave rise to extensive transferrin fibril structures. Optical microscopy and AFM studies showed that red blood cells (RBCs) readily adhere to these fibrils. Moreover, the fibrils appear to penetrate RBC membranes and to induce rapid cell destruction (within about 5 h). It is speculated that in situations in vivo where transferrin fibrils can form, such interactions might have adverse physiological consequences, and further studies could aid the understanding of related pathological events.     

Effects of alkali pretreatment on lyocell woven fabric and its influence on pilling properties

Abstract

Experiments were conducted to study the influence of various concentration of alkalis on the pilling properties of lyocell fabrics. Generally, the lyocell fabric has more tendency of pill formation due to fibrillation properties. Therefore, present work is focused on the impact of alkali pretreatments with various concentration from 0.5?mol/L to 3?mol/L on lyocell with their pilling resistance. Due to the morphological changes, pilling results are attributed to the alkali types and their concentration. Treatment with TmAH and LiOH at 2?mol/L shows the reduction of a number of fibrils leading to reduce the pill generation significantly. Carboxyl content and iodine sorption value are analyzed to find the impact of alkali on the accessible region and structural changes respectively, also surface modification was observed by SEM to confirm the surface characteristics. Overall results shows that the reduction of fibrillation leads to better pilling resistance of lyocell fabric.     

Direct Observation of Cavitation and Fibrillation in a Probe Tack Experiment on Model Acrylic Pressure-Sensitive-Adhesives

The adhesion mechanisms of two acrylic Pressure-Sensitive-Adhesives on a stainless steel probe are investigated with a custom-designed probe tack apparatus. Our setup allows the simultaneous acquisition of a nominal stress and strain curve, and the observation of the adhesive film from underneath the transparent substrate. The temperature was varied in the range -20°C to 50°C and the debonding rate in the range 1–10000 μm/s. For all conditions we observed, upon debonding, the formation of cavities at or near the interface between the probe and the film. These cavities initially grew predominantly in the plane of the film but, at higher values of nominal strain, the walls between the cavities were stretched in the direction normal to the plane of the ifim to become a fibrillar structure. The transition from a cavitated structure to a fibrillar one was only found within a time-temperature window of rheological properties of the adhesive, while the adhesion energy was found to be mainly related to the elongational properties of the adhesive. The maximum tensile stress observed in the probe tack experiment was directly related to the appearance of the cavities and showed a good correlation with the shear modulus of the adhesive, while the adhesion energy was found to be mainly related to the elongational properties of the adhesive. The presence of 2% acrylic acid as a comonomer had a negligible effect on the maximum stress but a very important one on the formation of a fibrillar structure and on the locus of failure.