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- Duong, T. C., et al.
(författare)
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A hierarchical computational thermodynamic and kinetic approach to discontinuous precipitation in the U-Nb system
- 2015
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Ingår i: PTM 2015 - Proceedings of the International Conference on Solid-Solid Phase Transformations in Inorganic Materials 2015. - : International Conference on Solid-Solid Phase Transformations in Inorganic Materials. - 9780692437360 ; , s. 887-894
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Konferensbidrag (refereegranskat)abstract
- U-Nb alloys decompose via discontinuous precipitation (DP) over a broad range of aging conditions, adversely affecting their properties. The growth kinetics, lamellar spacing, and Nb partitioning have been measured, but the thermodynamic and kinetic factors underlying these specific transformation characteristics and reaction paths, vis-a-vis the monotectoid reaction, are not fully resolved. In this work, a hierarchical computational thermodynamic and kinetic approach was carried out to investigate DP. The hierarchical approach started with density-functional theory (DFT) investigations of ground-state formation energies of bcc-based U-Nb alloys. The estimated energetic data was then utilized as an imposed first-principles-based constraint to improve the consistency of the CALPHAD thermodynamic and, subsequently, kinetic assessments of U-Nb. Phasefield simulations were then carried out to study DP's microstructure evolution using the assessed CALPHAD thermodynamic and kinetic representations. Good agreement with experiments on different physical/length scales was achieved, which validates the present theoretical contributions to a better understanding of DP in U-Nb alloys.
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- Harms, H. J., et al.
(författare)
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Cardiopulmonary transit time : A novel PET imaging biomarker of in vivo physiology for risk stratification of heart transplant recipients
- 2022
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Ingår i: Journal of Nuclear Cardiology. - : Springer Nature. - 1071-3581 .- 1532-6551. ; 29, s. 1234-1244
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Tidskriftsartikel (refereegranskat)abstract
- Background: Myocardial blood flow (MBF) can be quantified using dynamic PET studies. These studies also inherently contain tomographic images of early bolus displacement, which can provide cardiopulmonary transit times (CPTT) as measure of cardiopulmonary physiology. The aim of this study was to assess the incremental prognostic value of CPTT in heart transplant (OHT) recipients.Methods: 94 patients (age 56 +/- 16 years, 78% male) undergoing dynamic N-13-ammonia stress/rest studies were included, of which 68 underwent right-heart catherization. A recently validated cardiac allograft vasculopathy (CAV) score based on PET measures of regional perfusion, peak MBF and left-ventricular (LV) ejection fraction (LVEF) was used to identify patients with no, mild or moderate-severe CAV. Time-activity curves of the LV and right ventricular (RV) cavities were obtained and used to calculate the difference between the LV and RV bolus midpoint times, which represents the CPTT and is expressed in heartbeats. Patients were followed for a median of 2.5 years for the occurrence of major adverse cardiac events (MACE), including cardiovascular death, hospitalization for heart failure or acute coronary syndrome, or re-transplantation.Results: CPTT was significantly correlated with cardiac filling pressures (r = .434, P = .0002 and r = .439, P = .0002 for right atrial and pulmonary wedge pressure), cardiac output (r = - .315, P = .01) and LVEF (r = - .513, P < .0001). CPTT was prolonged in patients with MACE (19.4 +/- 6.0 vs 14.5 +/- 3.0 heartbeats, P < .001, N = 15) with CPTT >= 17.75 beats showing optimal discriminatory value in ROC analysis. CPTT >= 17.75 heartbeats was associated with a 10.1-fold increased risk (P < .001) of MACE and a 7.3-fold increased risk (P < .001) after adjusting for PET-CAV, age, sex and time since transplant.Conclusion: Measurements of cardiopulmonary transit time provide incremental risk stratification in OHT recipients and enhance the value of multiparametric dynamic PET imaging, particularly in identifying high-risk patients.
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- Shi, Z. J., et al.
(författare)
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Chorioamnionitis in the Development of Cerebral Palsy: A Meta-analysis and Systematic Review
- 2017
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Ingår i: Pediatrics. - : American Academy of Pediatrics (AAP). - 0031-4005 .- 1098-4275. ; 139:6
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Forskningsöversikt (refereegranskat)abstract
- CONTEXT: Chorioamnionitis (CA) has often been linked etiologically to cerebral palsy (CP). OBJECTIVES: To differentiate association from risk of CA in the development of CP. DATA SOURCES: PubMed, Cochrane Library, Embase, and bibliographies of original studies were searched by using the keywords (chorioamnionitis) AND ((cerebral palsy) OR brain). STUDY SELECTION: Included studies had to have: (1) controls, (2) criteria for diagnoses, and (3) neurologic follow-up. Studies were categorized based on: (1) finding incidence of CP in a CA population, or risk of CP; and (2) incidence of CA in CP or association with CP. DATA EXTRACTION: Two reviewers independently verified study inclusion and extracted data. RESULTS: Seventeen studies (125 256 CA patients and 5 994 722 controls) reported CP in CA. There was significantly increased CP inpreterm histologic chorioamnionitis (HCA; risk ratio [RR] = 1.34, P < .01), but not in clinical CA (CCA). Twenty-two studies (2513 CP patients and 8135 controls) reported CA in CP. There was increased CCA (RR = 1.43, P < .01), but no increase in IICA in preterm CP. Increased IICA was found (RR = 4.26, P < .05), as well as CCA in term/near-term CP (RR = 3.06, P < .01). CONCLUSIONS: The evidence for a causal or associative role of CA in CP is weak. Preterm HCA may be a risk factor for CP, whereas CCA is not. An association with term and preterm CP was found for CCA, but only with term CP for HCA.
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