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We present a three-dimensional multiscale elastohydrodynamic lubrication (EHL) contact model for chemical mechanical planarization (CMP) based on satisfying the fundamental mechanical force and moment balance equations appropriate for a rotational CMP tool. We describe surface-surface and fluid-surface interactions in conditions where pad asperities are in direct contact with the wafer and the effective film thickness is comparable in size to the roughness of the bounding surfaces. A hyperelastic material is used for our asperity scale model to account for large deformations of the soft polymer asperities. We iteratively solve the soft elastohydrodynamic contact problem, i.e., the solid-solid contact problem coupled with fluid pressure, until the global force and moment balances are satisfied for given operating conditions. The multiscale model computes contact stress across the wafer surface due to asperity deformation that is, in turn, caused by the externally applied load and interfacial slurry pressures. Finally, a relative measure of material removal rate across the wafer is represented by the computed local asperity contact stress. Flat, concave, and convex rigid wafers are considered. The work of this paper focuses on understanding fundamental mechanical aspects of CMP and presents a methodology to simulate mechanical aspects of the CMP process. © 2003 The Electrochemical Society. All rights reserved.

A “soft” elastohydrodynamic lubrication model for a conformal one-dimensional sliding contact is presented. We describe surface-surface and fluid-surface interactions in conditions where asperities are in direct contact (mixed lubrication), and the effective film thickness is comparable in size to the roughness of the bounding surfaces. In the conditions considered, surfaces have a low elastic modulus, and fluid pressures have a low magnitude, relative to those found in most tribology applications. An interesting coupling is exhibited between the surface roughness, the global elasticity, and the fluid pressure. As opposed to typical tribological applications in conformal mixed lubrication contact, fluid pressure is strong enough to cause significant elastic displacement of the mean boundary surfaces. The deformation is taken into account in an iterative process to compute the resulting spatially dependent stresses, deformations and fluid pressures.

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Highlights Differences in risk factors for SBI between paroxysmal and persistent AF was studied. NVAF patients (119 paroxysmal, 71 persistent) underwent brain MRI, TTE, and TEE. DM and CKD, which represents microvascular disease, predicted SBI in paroxysmal AF. There was no obvious therapeutic target for SBI after progression to persistent NVAF. Intervention for DM and CKD from paroxysmal NVAF may prevent SBI and future stroke.

<b><i>Introduction:</i></b> Silent brain infarction (SBI) is an independent risk factor for subsequent symptomatic stroke in the general population. Although aortic stenosis (AS) is also known to be associated with an increased risk of future symptomatic stroke, little is known regarding the prevalence and risk factors for SBI in patients with AS. <b><i>Methods:</i></b> The study population comprised 83 patients with severe AS with no history of stroke or transient ischemic attack and paralysis or sensory impairment (mean age 75 ± 7 years). All patients underwent brain magnetic resonance imaging to screen for SBI and multidetector-row computed tomography to quantify the aortic valve calcification (AVC) volume. Comprehensive transthoracic and transesophageal echocardiography were performed to evaluate left atrial (LA) abnormalities, such as LA enlargement, spontaneous echo contrast, or abnormal LA appendage emptying velocity (&#x3c;20 cm/s), and complex plaques in the aortic arch. <b><i>Results:</i></b> SBI was detected in 38 patients (46%). Multiple logistic regression analysis indicated that CHA₂DS₂-VASc score and estimated glomerular filtration rate (eGFR) were independently associated with SBI (<i>p</i> &#x3c; 0.05), whereas LA abnormalities and AVC volume were not. When patients were divided into 4 groups according to CHA₂DS₂-VASc score and eGFR, the group with a higher CHA₂DS₂-VASc score (≥4) and a lower eGFR (&#x3c;60 mL/min/1.73 m²) had a greater risk of SBI than the other groups (<i>p</i> &#x3c; 0.05). <b><i>Conclusion:</i></b> These findings indicate that AS is associated with a high prevalence of SBI, and that the CHA₂DS₂-VASc score and eGFR are useful for risk stratification.

Background: In patients with symptomatic severe aortic stenosis (AS), those who experienced readmission due to heart failure after transcatheter aortic valve replacement (TAVR) showed poor prognosis. Furthermore, poor BNP improvement is associated with increased morbidity and mortality. However, little is known about the clinical parameters related to the change in BNP levels after TAVR procedure.Methods and Results: This study population consisted of 127 consecutive patients of symptomatic severe AS with preserved ejection fraction (EF) who underwent TF-TAVR. The median BNP level was signi cantly decreased from 252.5 pg/ml to 146.8 pg/ml in all 127 patients 1 year after TF-TAVR (P<0.01). However, the patients could be divided into 2 groups according to decrease (72%) or increase (28%) in plasma BNP level. Multivariate logistic regression analysis revealed that AV peak velocity, preprocedural BNP, and larger left atrial volume index (LAVI) were found to be an independent predictor of increased BNP level 1 year after TAVR (OR 0.55, 95% CI 0.38-0.77; p<0.01). LAVI were negatively correlated with the change in BNP level before and 1 year after TAVR (r=0.47, P<0.01). The ROC analysis demonstrated that 52.9ml/m 2 was the optimal cut-off value of LAVI for decreasing BNP 1 year after TAVR (area under the curve 0.69) with 64% sensitivity and 70% speci city.Conclusions: In addition to AV peak velocity and pre-procedural BNP, LAVI independently predicts future improvement of BNP levels 1 year after TAVR. Our ndings indicate an additive predictive value of assessment of LAVI before TAVR procedure for risk strati cation.