Sung-Ki Kim

Local existence and blow-up criterion of Hölder continuous solutions of the Boussinesq equations

In this paper we prove the local existence and uniqueness of C 1+γ solutions of the Boussinesq equations with initial data υ 0 , θ 0 ∈ C 1+γ , ω 0 , ∇θ 0 ∈ L q for 0 q 2. We also obtain a blow-up criterion for this local solutions. More precisely we show that the gradient of the passive scalar θ controls the breakdown of C 1+γ solutions of the Boussinesq equations.

Post-maturation zona perforation improves porcine parthenogenetic trophoblast culture

This study was designed to optimize a method to improve porcine parthenogenetic embryo hatching and trophoblast culture. Mature oocytes (D0PPA) and day 6 blastocysts (D6PPA) were perforated with a 20 μm diameter needle for assisted hatching. The two groups showed a significant difference in hatching rate and blastocyst cell doubling when compared to a non-perforated control group. D0PPA blastocysts were able to form tertiary trophoblast colonies but D6PPA and control groups were not able to grow beyond primary colonies. Quantitative real-time PCR analysis showed significant differences in BAX, BAX/BCL2L1 and HSP70-2 mRNA expression between the experimental groups.

Performance analysis of a rapid thermal processor via physics-based modeling and convex optimization

Rapid thermal processing (RTP) is a key fabrication technology in the advanced cluster tool. Ever-decreasing feature sizes require extremely tight process control, which rely on a good chamber design. The empirical approach to the RTP design has its own limitations in two areas, although widely adopted and successful in delivering necessary performance specifications: (1) reduction in time-to-market and development cost and (2) quantification of performance limits. With the advent of powerful computing resources at relatively low cost, a model-based approach provides an alternative and has better chance to achieve optimal design by virtue of its capability to quantify performance limits at minimal time and cost. In an effort to realize the model-based approach, a physics-based model is derived and validated against experimental data. With a predictive model available, the performances of an RTP design are analyzed via convex optimization to qualify an RTP design, which also serves as a basis for control implementation once the RTP design parameters are set.

The Effect of Recurrent Glomerulonephritis and Acute Rejection Episodes in Zero Human Leukocyte Antigen-Mismatched Kidney Transplantation

BACKGROUND Although human leukocyte antigen (HLA)-identical renal transplantation achieves superior graft outcomes, it does not uniformly allow indefinite graft survival. Recurrence of the original disease and effects of acute rejection episodes (ARE) may preclude indefinite survival. Herein, we have analyzed the factors that affect the graft outcomes among HLA zero-mismatch cases. METHODS We performed a retrospective, single-center study to evaluate the effect of recurrent glomerulonephritis (GN) and ARE on outcomes of grafts with zero HLA-mismatches (n = 122) versus three to four mismatches (n = 317), and five to six mismatches (n = 102). Forty-one percent of patients had GN as underlying disease. RESULTS Overall graft survival was 92.4% at 5 years and 79.6% at 10 years. HLA incompatibility did not affect graft survival: zero versus three to four versus five to six mismatches = 92.8% versus 90.8% versus 95.8% at 5 years and 82.5% versus 74.3% versus 85.1% at 10 years, respectively (P = .399). Subgroup analysis for subjects with GN revealed that ARE (P = .001) and recurrent GN (P = .003) were the risk factors for graft loss, whereas living donation was protective (P = .029). ARE was more prevalent with greater HLA incompatibility [0 (reference) < three to four < five to six mismatches; P = .047 and P = .014]. However, recurrent GN showed the opposite trend [0 (reference) > three to four > five to six mismatches; P = .106 and P = .022]. Furthermore, graft loss due to recurrent GN was significant among the HLA zero versus the three- to four-mismatch group (P = .047). CONCLUSIONS Graft survival was not affected by the degree of HLA incompatibility, which was mainly due to the recurrence of underlying disease. Therefore, a main focus should be the management of recurrence, especially among HLA-identical kidney transplantations.

Assessment of blood flow velocity profiles in heart ventricles and aorta with phase contrast magnetic resonance imaging

Accurate measurement of blood flow is usually very difficult and invasive to make in spite of its important roles in clinical diagnosis. Therefore, an alternative method capable of determining the cardiac output non-invasively will be of good use. Furthermore, measurement of blood velocity with high resolution either in the heart or in any part of circulatory system without any cardiac catheterization would play an important role in the evaluation of patients with circulatory disorders. The MRI phase contrast technique (PC-MRI) can be used for this purpose. It can provide flow velocity information in addition to anatomic imaging by applying bipolar gradient in the velocity encoding direction. We can obtain velocity encoded MR images computed by the phase difference between two images acquired with different gradient first moments but identical zeroth moments. We combined phase contrast sequence and cine method to acquire the velocity map across the entire cardiac cycle. ECG gating was used for triggering. We calculated volume flow by pixel unit velocity analysis in the region of interest. Also by visualizing the velocity profile dynamically with 3D representation, we could assess more easily how the appearances of blood flow patterns are. The proposed method was tested both with a phantom where a pulsatile waveform was generated by ventricular assistance device and in vivo at the heart of normal volunteer on a GE 1.5 T scanner. As a conclusion, the dynamically represented 3D images obtained by the cine PC method could be confirmed as a good method for assessment of cardiac function.