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排序方式: 共有567条查询结果,搜索用时 578 毫秒
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Willem G de Voogt Ben F M Vonk Bert A Albers Florian Hintringer 《Europace : European pacing, arrhythmias, and cardiac electrophysiology》2004,6(6):561-569
Automatic capture detection systems are currently available in several cardiac pacing devices. All current systems use low-polarization electrodes and no beat to beat detection system is available for all types of electrodes. In addition the success ratio for currently available systems is not always 100%. Failure to detect capture reliably is often related to the behaviour of the electrode-tissue interface under different circumstances. Pacemaker electrodes can be considered electrochemical cells with complicated characteristics depending on time, temperature and electrical charge. This electrochemical cell is disturbed when a charge is transferred across the electrode-tissue interface during pacing. Several measures can be taken in order to minimise this disturbance or pace polarization artefact (PPA) including the use of high active surface area electrodes and application of tri-phasic pacing pulses. Another factor influencing detection of evoked potentials is the input circuit of the pacemaker affecting the PPA and the evoked response. Positive PPAs can be falsely interpreted as evoked potentials due to the undershoot of the second order filters applied in modern cardiac pacemakers. This paper explains the behaviour of the interface between the electrode and the cardiac tissue in combination with the pacemaker output circuits and input amplifiers under different circumstances. 相似文献
3.
荧光原位杂交技术分析人结肠菌群方法研究 总被引:2,自引:0,他引:2
建立荧光原位杂交技术分析人体内结肠菌群的方法。取受试者新鲜粪便 ,选用 5种特异性的 16SrRNA寡核苷酸探针 ,检测粪便样本收集后的保存时间、温度 ,离心条件及样本固定液存放时间对杂交计数结果的影响。结果建立最佳实验条件为 :粪便样本收集后应尽快在 4℃下保存 ,放置时间不要超过 12小时即作处理 ;样本的适宜离心条件为 70 0g 2分钟 ;样本用多聚甲醛固定后在 - 80℃下存放时间不要超过 5个月。该方法具有较好的稳定性 ,可以有效地检出个体之间结肠菌群的差异。 相似文献
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Sylwia M. Figarska H. Marike Boezen Judith M. Vonk 《European journal of epidemiology》2012,27(11):867-876
Dyspnea is a predictor of mortality. The effects of dyspnea severity and changes in dyspnea status on all-cause and cause-specific mortality remain unclear. The Vlagtwedde/Vlaardingen study started in 1965 and subjects were re-examined every 3?years until 1989/1990. Vital status of all 8,465 subjects on December 31st, 2008 was assessed. Associations between mortality and dyspnea severity and changes in dyspnea status were investigated using Cox regression adjusted for gender, age, FEV1 %predicted, place of residence, smoking and BMI. After 43?years of follow-up, 2,883 (39?%) of 7,360 subjects examined for dyspnea severity had died, 1,386 (19?%) due to cardiovascular disease, 267 (4?%) due to chronic obstructive pulmonary disease (COPD). Subjects with moderate and severe dyspnea had increased all-cause and cardiovascular mortality [moderate: HR?=?1.3 (95?% CI 1.2–1.5) and 1.4 (1.1–1.6), severe: 1.5 (1.1–2.0) and 1.9 (1.3–2.6) respectively] compared to asymptomatics. Severe dyspnea was significantly associated with COPD mortality [3.3 (2.0–5.2)]. Subjects who lost dyspnea had hazard ratios for all-cause and cause-specific mortality comparable to asymptomatics. Persistent dyspnea and dyspnea development were risk factors for all-cause, cardiovascular and COPD mortality [persistent: 2.0 (1.4–2.8), 1.9 (1.2–3.3) and 3.3 (1.2–8.9), development: 1.5 (1.2–1.8), 2.0 (1.5–2.6) and 3.8 (2.3–6.3) respectively]. Additionally, dyspnea effects on mortality were more pronounced in overweight/obese and older subjects and in subjects with better lung function. These results show that dyspnea is associated with mortality in a severity-dependent manner. Furthermore this study is the first showing that dyspnea remission normalizes mortality risk. Having or developing dyspnea is a risk factor for mortality. 相似文献
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Eleni Vradi Werner Brannath Thomas Jaki Richardus Vonk 《Journal of biopharmaceutical statistics》2018,28(4):735-749
The growing role of targeted medicine has led to an increased focus on the development of actionable biomarkers. Current penalized selection methods that are used to identify biomarker panels for classification in high-dimensional data, however, often result in highly complex panels that need careful pruning for practical use. In the framework of regularization methods, a penalty that is a weighted sum of the L1 and L0 norm has been proposed to account for the complexity of the resulting model. In practice, the limitation of this penalty is that the objective function is non-convex, non-smooth, the optimization is computationally intensive and the application to high-dimensional settings is challenging. In this paper, we propose a stepwise forward variable selection method which combines the L0 with L1 or L2 norms. The penalized likelihood criterion that is used in the stepwise selection procedure results in more parsimonious models, keeping only the most relevant features. Simulation results and a real application show that our approach exhibits a comparable performance with common selection methods with respect to the prediction performance while minimizing the number of variables in the selected model resulting in a more parsimonious model as desired. 相似文献
8.
Agnes D. Berendsen Lucienne A. Vonk Behrouz Zandieh‐Doulabi Vincent Everts Ruud A. Bank 《Journal of tissue engineering and regenerative medicine》2012,6(9):721-730
Collagen gels are promising scaffolds to prepare an implant for cartilage repair but several parameters, such as collagen concentration and composition as well as cell density, should be carefully considered, as they are reported to affect phenotypic aspects of chondrocytes. In this study we investigated whether the presence of collagen type I or II in gel lattices affects matrix contraction and relative gene expression levels of matrix proteins, MMPs and the subsequent degradation of collagen by goat articular chondrocytes. Only floating collagen I gels, and not those attached or composed of type II collagen, contracted during a culture period of 12 days. This coincided with an upregulation of both Mmp13 and ?14 gene expression, whereas Mmp1 expression was not affected. The release of hydroxyproline in the culture medium, indicating matrix degradation, was increased five‐fold in contracted collagen I gels compared to collagen II gels without contraction. Furthermore, blocking contraction of collagen I gels by cytochalasin B inhibited Mmp13 and ?14 expression and the release of hydroxyproline. The expression of cartilage‐specific ECM genes was decreased in contracted collagen I gels, with increased numbers of cells with an elongated morphology, suggesting that matrix contraction induces dedifferentiation of chondrocytes into fibroblast‐like cells. We conclude that the collagen composition of the gels affects matrix contraction by articular chondrocytes and that matrix contraction induces an increased Mmp13 and ?14 expression as well as matrix degradation. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
9.
Zhan L CAO WC de Vlas S Xie SY Zhang PH WU XM Dumler JS Yang H Richardus JH Habbema JD 《Vector borne and zoonotic diseases (Larchmont, N.Y.)》2008,8(3):369-380
Anaplasma phagocytophilum was detected by polymerase chain reaction in 13 (14.1%) of 92 rodents captured from a mountainous area of Zhejiang Province in southeastern China. The nucleotide sequences of 1442-bp, nearly entire 16S rRNA gene amplified from these rodents, had 100% identity, but varied from all known corresponding sequences of A. phagocytophilum deposited in GenBank. To further identify and classify the variant, fragments of 357-bp partial citrate synthase gene (gltA), 849-bp major surface protein 4 gene (msp4), and 443-bp groESL heat-shock operon gene, were amplified and analyzed. The nucleotide sequences of the partial gltA gene amplified from the rodents were identical to each other, but distinct from previously reported A. phagocytophilum sequences,as were msp4 and groESL. These findings indicate that the newly discovered agent represents a novel A. phagocytophilum variant. 相似文献
10.
Jasper Vonk Jaron Grard de Wit Floris Jan Voskuil Max Johannes Hendrikus Witjes 《Oral diseases》2021,27(1):21-26
Early diagnosis and radical surgical excision of oral squamous cell carcinomas are essential for achieving optimal treatment outcomes. To date, diagnostic tools that rely on anatomical anomalies provide limited information and resolution in clinical practice. As a result, oral cancer is often detected in an advanced stage. Also, no reliable real‐time intraoperative tools are readily available for the evaluation of surgical resection margins. Fluorescence imaging visualises biological processes that occur in early carcinogenesis and could, therefore, enable detection of small tumours in early stages. Furthermore, due to the high sensitivity and spatial resolution, fluorescence imaging could assist in resection margin assessment during surgery. In this review, we discuss several techniques that employ fluorescence for early diagnosis and surgical guidance in oral squamous cell carcinoma and present future perspectives on the potential of fluorescence imaging in oral cancer in the near future. 相似文献