Papers by CHUNG OONG CHANG
Statistica Sinica
The issue of combining individual p-values to aggregate multiple small effects is a longstanding ... more The issue of combining individual p-values to aggregate multiple small effects is a longstanding statistical topic. Many classical methods are designed for combining independent and frequent signals using the sum of transformed p-values with the transformation of lighttailed distributions, in which Fisher's method and Stouffer's method are the most well-known. In recent years, advances in big data promoted methods to aggregate correlated, sparse and weak signals; among them, Cauchy and harmonic mean combination tests were proposed to robustly combine p-values under "arbitrary" dependency structure. Both of the proposed tests are the transformation of heavy-tailed distributions for improved power with the sparse signal. Motivated by this observation, we investigate the transformation of regularly varying distributions, which is a rich family of heavy-tailed distribution, to explore the conditions for a method to possess robustness to dependency. We show that only an equivalent class of Cauchy and harmonic mean tests has sufficient robustness to dependency in a practical sense. We also show an issue caused by large negative penalty in the Cauchy method and propose a simple, yet practical modification with fast computation. Finally, we present simulations and apply to a neuroticism GWAS application to verify the discovered theoretical insights.
Cancers, 2021
Cervical squamous cell carcinoma (CESC) is one of the most common malignant tumors in women world... more Cervical squamous cell carcinoma (CESC) is one of the most common malignant tumors in women worldwide with a low survival rate. Acetyl coenzyme A synthase 2 (ACSS2) is a conserved nucleosidase that converts acetate to acetyl-CoA for energy production. Our research intended to identify the correlations of ACSS2 with clinical prognosis and tumor immune infiltration in CESC. ACSS2 is highly expressed in many tumors and is involved in the progression and metastasis of these tumors. However, it is not clear how ACSS2 affects CESC progression and immune infiltration. Analysis of the cBioPortal, GEPIA2, UALCAN, and TCGA databases showed that ACSS2 transcript levels were significantly upregulated in multiple cancer types including CESC. Quantitative RT-PCR analysis confirmed that ACSS2 expression was significantly upregulated in human cervical cancer cells. Here, we performed tissue microarray analysis of paraffin-embedded tissues from 240 cervical cancer patients recorded at FIGO/TNM cance...
Journal of the Chinese Institute of Engineers, 1997
ABSTRACT
PloS one, 2017
It is often helpful to classify biomarker values into groups of different risk levels to facilita... more It is often helpful to classify biomarker values into groups of different risk levels to facilitate evaluation of a biological, physiological, or pathological state. Stratification of patients into two risk groups is commonly seen, but there is always need for more than two groups for fine assessment. So far, there are no standard methods or tools to help decide how many cutoff points are optimal. In this study, we developed a comprehensive package that included methods to determine both the optimal number and locations of cutoff points for both survival data and dichotomized outcome. We illustrated workflow of this package with data from 797 patients with cervical cancer. By analyzing several risk factors of cervical cancer such as tumor size, body mass index (BMI), number of lymph nodes involved and depth of stromal invasion, in relation to survival and clinical outcome such as lymph nodal metastasis and lymphovascular invasion, we demonstrated that the best choice for BMI and str...
Proceedings of 2011 Cross Strait Quad-Regional Radio Science and Wireless Technology Conference, 2011
(MIB) fractal patch resonator are proposed in this paper. The BPF is mainly formed by a square pa... more (MIB) fractal patch resonator are proposed in this paper. The BPF is mainly formed by a square patch resonator in which a MIB fractal configuration with 2nd order iteration is embedded in the patch. By the perturbation and the T -couple/inter-di gital coupling, the wide-band and dual band responses are obtained respectively. For wide-band design, at 2.41 GHz it has
British journal of anaesthesia, Jan 10, 2015
Liver transplant recipients frequently develop acute kidney injury (AKI), but the predisposing fa... more Liver transplant recipients frequently develop acute kidney injury (AKI), but the predisposing factors and long-term consequences of AKI are not well understood. The aims of this study were to identify predisposing factors for early post-transplant AKI and the impact of AKI on patient and graft survival and to construct a model to predict AKI using clinical variables. In this 5-year retrospective study, we analysed clinical and laboratory data from 424 liver transplant recipients from our centre. By 72 h post-transplant, 221 patients (52%) had developed AKI [according to the Kidney Disease Improving Global Outcomes (KDIGO) criteria]. Predisposing factors for development of AKI were female sex, weight (>100 kg), severity of liver disease (Child-Pugh score), pre-existing diabetes mellitus, number of units of blood or fresh frozen plasma transfused during surgery, and non-alcoholic steatohepatitis as the aetiology of end-stage liver disease (P≤0.05). Notably, preoperative serum crea...
Journal of gynecologic oncology, 2014
The objective of this study was to explore the association of longitudinal CA-125 measurements wi... more The objective of this study was to explore the association of longitudinal CA-125 measurements with overall survival (OS) time by developing a flexible model for patient-specific CA-125 profiles, and to provide a simple and reliable prediction of OS. A retrospective study was performed on 275 patients with ovarian cancer who underwent at least one cycle of primary chemotherapy in our institute. Serial measurements of patients' CA-125 levels were performed at different frequencies according to their clinical plans. A statistical model coupling the Cox proportional hazards and the mixed-effects models was applied to determine the association of OS with patient-specific longitudinal CA-125 values. Stage and residual tumor size were additional variables included in the analysis. A total of 1,601 values of CA-125 were included. Longitudinal CA-125 levels, stage, and the residual tumor size were all significantly associated with OS. A patient-specific survival probability could be cal...
39th Aerospace Sciences Meeting and Exhibit, 2001
In this paper, we report the experience of calculating three-dimensional detonations by the Space... more In this paper, we report the experience of calculating three-dimensional detonations by the Space-Time Conservation Element and Solution Element (CE/SE) Method using a cost-effective Beowulf cluster. The Time-Surfer, a 16-processor PC cluster, was built and tested as part of this effort. The total cost was about twenty thousand 1999-dollars. The efficiency and accuracy of the CE/SE method on the Beowulf cluster are assessed to determine feasibility of applying the CE/SE method to CFD calculations of using five million mesh nodes and above on this low-cost platform. The numerical solutions of threedimensional detonations propagating in a square tube are calculated. The diagonal instability pattern of three-dimensional detonations is reported.
Alzheimer's disease (AD) is a chronic neurodegenerative disease, serving as the most common form ... more Alzheimer's disease (AD) is a chronic neurodegenerative disease, serving as the most common form of dementia among the elderly population. AD targets various neurological processes in humans such as the visual pathway and hence resulting in various forms of visual abnormalities. Several studies have reported the loss of retinal ganglion cells, reduced thickness of nerve fibre layers (NFL) and damage of the optic nerve head and fiber layers. These findings suggest a putative link between AD and visual function deficits. As genetic defects have been found to be associated with AD, it is possible to experimentally mimic this condition in animal models. AD gene mutations discovered in human amyloid precursor protein (APP), presenilin 1/2 (PS1/PS2) and microtubuleassociated tau protein have been used to engineer AD animal models. In this review, we discuss the underlying molecular mechanisms of AD in terms of amyloidogenesis and tauopathies, as well as explain the pathological changes leading to vision loss in AD patients. Subsequently, the biology of the genes/proteins which have a causative link to AD, including APP, PS1 and PS2 will be discussed. Several recent reports of retinal degeneration in AD transgenic mouse models are selected to examine the relationship between AD and visual disturbance. We believe that a wellestablished method to generate transgenic mice will enhance our understanding of AD pathology and its correlation with retinal degeneration, leading to possible detection and treatment methods for AD.
Journal of gynecologic oncology, 2018
The objective was to identify risk factors that were associated with the progression from endomet... more The objective was to identify risk factors that were associated with the progression from endometriosis to ovarian cancer based on medical insurance data. The study was performed on a dataset obtained from the National Health Insurance Research Database, which covered all the inpatient claim data from 2000 to 2013 in Taiwan. The International Classification of Diseases (ICD) code 617 was used to screen the dataset for the patients who were admitted to hospital due to endometriosis. They were then tracked for subsequent diagnosis of ovarian cancer, and available biological, socioeconomic and clinical information was also collected. Univariate and multivariate analyses were then performed based on the Cox regression model to identify risk factors. C-index was calculated and cross validated. A total of 229,617 patients who were admitted to hospital due to endometriosis from 2000 to 2013 were included in the study, out of whom 1,473 developed ovarian cancer by the end of 2013. A variety...
Biomolecules, 2020
Cervical cancer is a common gynecological malignancy, accounting for 10% of all gynecological can... more Cervical cancer is a common gynecological malignancy, accounting for 10% of all gynecological cancers. Recently, targeted therapy for cervical cancer has shown unprecedented advantages. Several studies have shown that ubiquitin conjugating enzyme E2 (UBE2C) is highly expressed in a series of tumors, and participates in the progression of these tumors. However, the possible impact of UBE2C on the progression of cervical squamous cell carcinoma (CESC) remains unclear. Here, we carried out tissue microarray analysis of paraffin-embedded tissues from 294 cervical cancer patients with FIGO/TNM cancer staging records. The results indicated that UBE2C was highly expressed in human CESC tissues and its expression was related to the clinical characteristics of CESC patients. Overexpression and knockdown of UBE2C enhanced and reduced cervical cancer cell proliferation, respectively, in vitro. Furthermore, in vivo experiments showed that UBE2C regulated the expression and activity of the mTOR/...
Molecular Cancer Research, 2006
The tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) can trigger growth inhibition, epit... more The tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) can trigger growth inhibition, epithelial-mesenchymal transition (EMT)–like cell scattering, and migration of hepatoma cells HepG2 in a protein kinase C-α (PKC-α)–dependent manner. Saikosaponin a, an ingredient of antitumorigenic Chinese herb Sho-Saiko-to, inhibited cell growth but did not induce EMT-like cell scattering and cell migration of HepG2. Saikosaponin a and TPA induced transient (for 30 minutes) and sustained (until 6 hours) phosphorylation of extracellular signal-regulated kinase (ERK), respectively. Generation of the reactive oxygen species (ROS) was induced by TPA, but not saikosaponin a, for 3 hours. As expected, scavengers of ROS, such as superoxide dismutase, catalase, and mannitol, and the thiol-containing antioxidant N-acetylcystein dramatically suppressed the TPA-triggered cell migration but not growth inhibition of HepG2. The generation of ROS induced by TPA was PKC, but not ERK, dependent. On the oth...
Journal of Multivariate Analysis, 2009
In many areas of application, the data are of functional nature, such as (one-dimensional) spectr... more In many areas of application, the data are of functional nature, such as (one-dimensional) spectral data and two-or three-dimensional imaging data. It is often of interest to test for the significance of some set of factors in the functional observations (e.g., test for the mean differences between two groups). Testing hypotheses point-by-point (voxelby-voxel in neuroimaging studies) results in a severe multiple-comparisons problem as the number of measurements made per observation is typically much larger than the number of observations (''large p, small n''). Thus solutions to this problem should take into account the spatial correlation structure inherent in the data. Popular approaches in such a setting include the general Statistical Parametric Mapping (SPM) approach and the permutation test, but these rely on strong parametric and exchangeability assumptions. In situations in which these assumptions are not satisfied, a nonparametric multiplier bootstrap approach may be used. Motivated by this problem, we present general results for multiplier bootstraps for sums of independent but not identically distributed processes. We also consider the application of these results to an imaging setting and provide sufficient conditions that will ensure asymptotic control of the familywise error rate.
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Papers by CHUNG OONG CHANG