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- Chen, Baowei, et al.
(author)
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Methylation mechanism of tin(II) by methylcobalamin in aquatic systems
- 2007
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In: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 68:3, s. 414-419
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Journal article (peer-reviewed)abstract
- The methylation reaction of tin(II) with methylcobalamin (CH(3)B(12)) in aquatic systems was modeled in the laboratory. The products were detected by a sensitive gas chromatography-flame photometric detector (GC-FPD), and further identified by gas chromatography-mass spectrometry (GC-MS). Both monomethyltin (MMT) and dimethyltin (DMT) were found as methylation products. Three important effecting factors during the methylation reaction, salinity, pH and aerobic or anaerobic, were studied. The results showed that methyl group can be transferred from CH(3)B(12) to tin in aquatic solutions as a radical or carbonium, as well as a carbanion. Two explanations for the pH-dependency of the methylation reaction between tin(II) and CH(3)B(12) were proposed: pH-dependency of the equilibrium states of CH(3)B(12), and pH-dependency of inorganic tin(II) species whose reactivity vary with the redox potential in the solution. Salinity can influence the activity of the methyl donor, which cause changes in the methylation efficiency. Kinetic experiments showed that the methylation reaction was pseudo-first-order for CH(3)B(12).
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| 3. |
- Kou, Wen, et al.
(author)
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A 3D numerical simulation of stress distribution and fracture process in a zirconia-based FPD framework
- 2011
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In: Journal of Biomedical Materials Research. Part B - Applied biomaterials. - : John Wiley & Sons. - 1552-4973 .- 1552-4981. ; 96B:2, s. 376-385
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Journal article (peer-reviewed)abstract
- In this study, a numerical approach to the fracture behavior in a three-unit zirconia-based fixed partial denture (FPD) framework was made under mechanical loading using a newly developed three-dimensional (3D) numerical modeling code. All the materials studied were treated heterogeneously and Weibull distribution law was applied to describe the heterogeneity. The Mohr-Coulomb failure criterion with tensile strength cut-off was utilized to judge whether the material was in an elastic or failed state. For validation, the fracture pattern obtained from the numerical modeling was compared with a laboratory test; they largely correlated with each other. Similar fracture initiation sites were detected both in the numerical simulation and in an earlier fractographic analysis. The numerical simulation applied in this study clearly described the stress distribution and fracture process of zirconia-based FPD frameworks, information that could not be gained from the laboratory tests alone. Thus, the newly developed 3D numerical modeling code seems to be an efficient tool for prediction of the fracture process in ceramic FPD frameworks.
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| 4. |
- Kou, Wen, et al.
(author)
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Numerical simulation of the fracture process in ceramic FPD frameworks caused by oblique loading
- 2015
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In: Journal of The Mechanical Behavior of Biomedical Materials. - : Elsevier BV. - 1751-6161 .- 1878-0180. ; 50, s. 206-214
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Journal article (peer-reviewed)abstract
- Using a newly developed three-dimensional (3D) numerical modeling code, an analysis was performed of the fracture behavior in a three-unit ceramic-based fixed partial denture (FPD) framework subjected to oblique loading. All the materials in the study were treated heterogeneously; Weibull׳s distribution law was applied to the description of the heterogeneity. The Mohr-Coulomb failure criterion with tensile strength cut-off was utilized in judging whether the material was in an elastic or failed state. The simulated loading area was placed either on the buccal or the lingual cusp of a premolar-shaped pontic with the loading direction at 30°, 45°, 60°, 75° or 90° angles to the occlusal surface. The stress distribution, fracture initiation and propagation in the framework during the loading and fracture process were analyzed. This numerical simulation allowed the cause of the framework fracture to be identified as tensile stress failure. The decisive fracture was initiated in the gingival embrasure of the pontic, regardless of whether the buccal or lingual cusp of the pontic was loaded. The stress distribution and fracture propagation process of the framework could be followed step by step from beginning to end. The bearing capacity and the rigidity of the framework vary with the loading position and direction. The framework loaded with 90° towards the occlusal surface has the highest bearing capacity and the greatest rigidity. The framework loaded with 30° towards the occlusal surface has the least rigidity indicating that oblique loading has a major impact on the fracture of ceramic frameworks.
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| 5. |
- Reynolds, Harmony R., et al.
(author)
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Association of Sex With Severity of Coronary Artery Disease, Ischemia, and Symptom Burden in Patients With Moderate or Severe Ischemia Secondary Analysis of the ISCHEMIA Randomized Clinical Trial
- 2020
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In: JAMA cardiology. - : American Medical Association (AMA). - 2380-6583 .- 2380-6591. ; 5:7, s. 773-786
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Journal article (peer-reviewed)abstract
- Key PointsQuestion When considering patients who have obstructive coronary artery disease and ischemia on stress testing, are there sex differences in severity of coronary artery disease, ischemia, and/or symptoms?Findings In this secondary analysis of the ISCHEMIA randomized clinical trial of 5179 patients, women had more frequent angina, less extensive coronary artery disease, and less severe ischemia than men. On multivariate analysis, female sex was independently associated with greater angina frequency.Meaning There may be inherent sex differences in the complex relationships between angina, ischemia, and atherosclerosis that may have implications for testing and treatment of patients with suspected coronary artery disease.AbstractImportance While many features of stable ischemic heart disease vary by sex, differences in ischemia, coronary anatomy, and symptoms by sex have not been investigated among patients with moderate or severe ischemia. The enrolled ISCHEMIA trial cohort that underwent coronary computed tomographic angiography (CCTA) was required to have obstructive coronary artery disease (CAD) for randomization.Objective To describe sex differences in stress testing, CCTA findings, and symptoms in ISCHEMIA trial participants.Design, Setting, and Participants This secondary analysis of the multicenter ISCHEMIA randomized clinical trial analyzed baseline characteristics of patients with stable ischemic heart disease. Individuals were enrolled from July 2012 to January 2018 based on local reading of moderate or severe ischemia on a stress test, after which blinded CCTA was performed in most. Core laboratories reviewed stress tests and CCTAs. Participants with no obstructive CAD or with left main CAD of 50% or greater were excluded. Those who met eligibility criteria including CCTA (if performed) were randomized to a routine invasive or a conservative management strategy (N = 5179). Angina was assessed using the Seattle Angina Questionnaire. Analysis began October 1, 2018.Interventions CCTA and angina assessment.Main Outcomes and Measures Sex differences in stress test, CCTA findings, and symptom severity.Results Of 8518 patients enrolled, 6256 (77%) were men. Women were more likely to have no obstructive CAD (<50% stenosis in all vessels on CCTA) (353 of 1022 [34.4%] vs 378 of 3353 [11.3%]). Of individuals who were randomized, women had more angina at baseline than men (median [interquartile range] Seattle Angina Questionnaire Angina Frequency score: 80 [70-100] vs 90 [70-100]). Women had less severe ischemia on stress imaging (383 of 919 [41.7%] vs 1361 of 2972 [45.9%] with severe ischemia; 386 of 919 [42.0%] vs 1215 of 2972 [40.9%] with moderate ischemia; and 150 of 919 [16.4%] vs 394 of 2972 [13.3%] with mild or no ischemia). Ischemia was similar by sex on exercise tolerance testing. Women had less extensive CAD on CCTA (205 of 568 women [36%] vs 1142 of 2418 men [47%] with 3-vessel disease; 184 of 568 women [32%] vs 754 of 2418 men [31%] with 2-vessel disease; and 178 of 568 women [31%] vs 519 of 2418 men [22%] with 1-vessel disease). Female sex was independently associated with greater angina frequency (odds ratio, 1.41; 95% CI, 1.13-1.76).Conclusions and Relevance Women in the ISCHEMIA trial had more frequent angina, independent of less extensive CAD, and less severe ischemia than men. These findings reflect inherent sex differences in the complex relationships between angina, atherosclerosis, and ischemia that may have implications for testing and treatment of patients with suspected stable ischemic heart disease.
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