An In-Depth Examination of a Thermodynamic Framework for the Phase-Field Crystal Model.

In this dissertation, we examine the phase-field crystal (PFC) model, which is a simulation method for modeling atomistic phenomena on diffusive time scales. We develop thermodynamic relationships that are used to derive procedures for calculating equilibrium material properties from the PFC model. The first set of relationships links the PFC free energy to thermodynamic state variables and are based on the thermodynamic formalism for crystalline solids [Larche and Cahn, Acta Metall., 21 1051 (1973)]. These relationships are employed to examine the thermodynamic processes associated with varying the input parameters of the PFC model. The equilibrium conditions between bulk solid and liquid phases are imposed on the relationships to obtain a procedure for determining solid-liquid phase coexistence. The resulting procedure is found to be in agreement with the common-tangent construction commonly used in the PFC community. We apply the procedure to an eighth-order-fit (EOF) PFC model that has been parameterized to body-centered-cubic (bcc) Fe [Jaatinen et al., PRE 80, 031602 (2009)] and demonstrate that the model does not predict stable bcc structures with positive vacancy densities. The second set of relationships is built on the recent work of Pisutha-Arnond et al. [Pisutha-Arnond et al., PRB, 87 014103 (2013)], and is applied to develop a thermodynamically consistent procedure for determining elastic constants from the PFC model. To implement these procedures, we present two alternative deformation methods, one in real space and the other in Fourier space, that are computationally more accurate and efficient than the method conventionally used in the PFC community. The procedure for determining elastic constants is implemented with the Fourier space deformation method to calculate bulk mechanical properties from the EOF-PFC model. Finally, we present a structural PFC model [Greenwood et al. PRL 105, 045702 (2010)] that yields a stable dc structure. The stabilization of a dc structure is accomplished by constructing a two-body direct correlation function (DCF) approximated by a combination of two Gaussian functions in Fourier space. A phase diagram that contains a dc-liquid phase coexistence region was constructed for the model. We examine the energies of the (100), (110), and (111) solid-liquid interfaces.PhDMaterials Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111344/1/vicchan_1.pd

Development of Self-Compacting Engineered Cementitious Composites

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/84749/1/iwscc_self-c_ecc_98.pd

Are Preoperative Kattan and Stephenson Nomograms Predicting Biochemical Recurrence after Radical Prostatectomy Applicable in the Chinese Population?

Purpose. Kattan and Stephenson nomograms are based on the outcomes of patients with prostate cancer recruited in the USA, but their applicability to Chinese patients is yet to be validated. We aim at studying the predictive accuracy of these nomograms in the Chinese population. Patients and Methods. A total of 408 patients who underwent laparoscopic or open radical resection of prostate from 1995 to 2009 were recruited. The preoperative clinical parameters of these patients were collected, and they were followed up regularly with PSA monitored. Biochemical recurrence was defined as two or more consecutive PSA levels >0.4 ng/mL after radical resection of prostate or secondary cancer treatment. Results. The overall observed 5-year and 10-year biochemical recurrence-free survival rates were 68.3% and 59.8%, which was similar to the predicted values by the Kattan and Stephenson nomograms, respectively. The results of our study achieved a good concordance with both nomograms (Kattan: 5-years, 0.64; Stephenson: 5-years, 0.62, 10-years, 0.71). Conclusions. The incidence of prostate cancer in Hong Kong is increasing together with the patients’ awareness of this disease. Despite the fact that Kattan nomograms were derived from the western population, it has been validated in our study to be useful in Chinese patients as well

Age effect on the characteristics of fibre/cement interfacial properties

The experimental findings of an investigation on the age development of interfacial properties of polyethylene fibers in a cementitious matrix are reported. It was found that the interfacial bond strength matures much faster, in less than 7 days, in comparison with bulk property development, which typically takes 14–28 days. A parallel ESEM study of the microstructure development in the interfacial transition zone supported the fact that the rapid early age saturation of the interfacial adhesive bond strength is associated with the growth of a CH rim around the fibre periphery. The formation of the CH layer appears to be completed much earlier than the hydration process of the bulk material. The slip-dependent friction after initial debonding was found to develop with age up to 28 days, gradually converting from a slip-weakening to a slip-hardening behaviour. These findings should be useful in interpreting early age fibre-reinforced cementitious composite properties.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44741/1/10853_2004_Article_175616.pd

Gate-Controlled Ionization and Screening of Cobalt Adatoms on a Graphene Surface

We describe scanning tunneling spectroscopy (STS) measurements performed on individual cobalt (Co) atoms deposited onto backgated graphene devices. We find that Co adatoms on graphene can be ionized by either the application of a global backgate voltage or by the application of a local electric field from a scanning tunneling microscope (STM) tip. Large screening clouds are observed to form around Co adatoms ionized in this way, and we observe that some intrinsic graphene defects display a similar behavior. Our results provide new insight into charged impurity scattering in graphene, as well as the possibility of using graphene devices as chemical sensors.Comment: 19 pages, 4 figure

Safety of two-dose COVID-19 vaccination (BNT162b2 and CoronaVac) in adults with cancer: a territory-wide cohort study

BACKGROUND: The World Health Organization has defined a list of adverse events of special interest (AESI) for safety surveillance of vaccines. AESI have not been adequately assessed following COVID-19 vaccination in patients with cancer contributing to vaccine hesitancy in this population. We aimed to evaluate the association between BNT162b2 and CoronaVac vaccines and the risk of AESI in adults with active cancer or a history of cancer. PATIENTS AND METHODS: We conducted a territory-wide cohort study using electronic health records managed by the Hong Kong Hospital Authority and vaccination records provided by the Department of Health. Patients with a cancer diagnosis between January 1, 2018, and September 30, 2021, were included and stratified into two cohorts: active cancer and history of cancer. Within each cohort, patients who received two doses of BNT162b2 or CoronaVac were 1:1 matched to unvaccinated patients using the propensity score. Cox proportional hazards regression was used to estimate hazard ratios (HR) and 95% confidence intervals (CIs) for AESI 28 days after the second vaccine dose. RESULTS: A total of 74,878 patients with cancer were included (vaccinated: 25,789 [34%]; unvaccinated: 49,089 [66%]). Among patients with active cancer, the incidence of AESI was 0.31 and 1.02 per 10,000 person-days with BNT162b2 versus unvaccinated patients and 0.13 and 0.88 per 10,000 person-days with CoronaVac versus unvaccinated patients. Among patients with history of cancer, the incidence was 0.55 and 0.89 per 10,000 person-days with BNT162b2 versus unvaccinated patients and 0.42 and 0.93 per 10,000 person-days with CoronaVac versus unvaccinated patients. Neither vaccine was associated with a higher risk of AESI for patients with active cancer (BNT162b2: HR 0.30, 95% CI 0.08-1.09; CoronaVac: 0.14, 95% CI 0.02-1.18) or patients with history of cancer (BNT162b2: 0.62, 95% CI 0.30-1.28; CoronaVac: 0.45, 95% CI 0.21-1.00). CONCLUSIONS: In this territory-wide cohort study of patients with cancer, the incidence of AESI following vaccination with two doses of either BNT162b2 or CoronaVac vaccines was low. The findings of this study can reassure clinicians and patients with cancer about the overall safety of BNT162b2 and CoronaVac in patients with cancer, which could increase the COVID-19 vaccination rate in this vulnerable group of patients

Endothelial Progenitors: A Consensus Statement on Nomenclature

Endothelial progenitor cell (EPC) nomenclature remains ambiguous and there is a general lack of concordance in the stem cell field with many distinct cell subtypes continually grouped under the term “EPC.” It would be highly advantageous to agree on standards to confirm an endothelial progenitor phenotype and this should include detailed immunophenotyping, potency assays, and clear separation from hematopoietic angiogenic cells which are not endothelial progenitors. In this review, we seek to discourage the indiscriminate use of “EPCs,” and instead propose precise terminology based on defining cellular phenotype and function. Endothelial colony forming cells and myeloid angiogenic cells are examples of two distinct and well‐defined cell types that have been considered EPCs because they both promote vascular repair, albeit by completely different mechanisms of action. It is acknowledged that scientific nomenclature should be a dynamic process driven by technological and conceptual advances; ergo the ongoing “EPC” nomenclature ought not to be permanent and should become more precise in the light of strong scientific evidence. This is especially important as these cells become recognized for their role in vascular repair in health and disease and, in some cases, progress toward use in cell therapy. Stem Cells Translational Medicine 2017;6:1316–132