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Search Results: 1 - 10 of 1020 matches for " Vui Pham "
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H?lder-Type Global Error Bounds for Non-degenerate Polynomial Systems
Si Tiep Dinh,Ha Huy Vui,Pham Tien Son
Mathematics , 2014,
Abstract: Let $F := (f_1, \ldots, f_p) \colon {\Bbb R}^n \to {\Bbb R}^p$ be a polynomial map, and suppose that $S := \{x \in {\Bbb R}^n \ : \ f_i(x) \le 0, i = 1, \ldots, p\} \ne \emptyset.$ Let $d := \max_{i = 1, \ldots, p} \deg f_i$ and $\mathcal{H}(d, n, p) := d(6d - 3)^{n + p - 1}.$ Under the assumption that the map $F \colon {\Bbb R}^n \rightarrow {\Bbb R}^p$ is convenient and non-degenerate at infinity, we show that there exists a constant $c > 0$ such that the following so-called {\em H\"older-type global error bound result} holds $$c d(x,S) \le [f(x)]_+^{\frac{2}{\mathcal{H}(2d, n, p)}} + [f(x)]_+ \quad \textrm{ for all } \quad x \in \mathbb{R}^n,$$ where $d(x, S)$ denotes the Euclidean distance between $x$ and $S,$ $f(x) := \max_{i = 1, \ldots, p} f_i(x),$ and $[f(x)]_+ := \max \{f(x), 0 \}.$ The class of polynomial maps (with fixed Newton polyhedra), which are non-degenerate at infinity, is generic in the sense that it is an open and dense semi-algebraic set. Therefore, H\"older-type global error bounds hold for a large class of polynomial maps, which can be recognized relatively easily from their combinatoric data.
Adenylate Kinase 3 Sensitizes Cells to Cigarette Smoke Condensate Vapor Induced Cisplatin Resistance
Xiaofei Chang,Rajani Ravi,Vui Pham,Atul Bedi,Aditi Chatterjee,David Sidransky
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0020806
Abstract: The major established etiologic risk factor for bladder cancer is cigarette smoking and one of the major antineoplastic agents used for the treatment of advanced bladder cancer is cisplatin. A number of reports have suggested that cancer patients who smoke while receiving treatment have lower rates of response and decreased efficacy of cancer therapies.
Clinical significance of heterotopic gastric mucosal patch of the proximal esophagus
Vui Heng Chong
World Journal of Gastroenterology , 2013, DOI: 10.3748/wjg.v19.i3.331
Abstract: Heterotopic gastric mucosa of the proximal esophagus (HGMPE), also referred to as “inlet patch” or “cervical inlet patch”, is a salmon colored patch that is usually located just distal to the upper esophageal sphincter. HGMPE is uncommon with endoscopic studies reporting a prevalence ranging from less than one percent to 18%. Most HGMPE are asymptomatic and are detected incidentally during endoscopy for evaluations of other gastrointestinal complaints. Most consider HGMPE as clinically irrelevant entity. The clinical significance of HGMPE is mainly acid related or neoplastic transformation. The reported prevalence of laryngopharyngeal reflux symptoms varies from less than 20% to as high as 73.1%. However, most of these symptoms are mild. Clinically significant acid related complications such as bleeding, ulcerations, structure and fistulization have been reported. Although rare, dysplastic changes and malignancies in association with HGMPE have also been reported. Associations with Barrett’s esophagus have also been reported but the findings so far have been conflicting. There are still many areas that are unknown or not well understood and these include the natural history of HGMPE, risk factors for complications, role of Helicobacter pylori infection and factors associated with malignant transformations. Follow-up may need to be considered for patients with complications of HGMPE and surveillance if biopsies show intestinal metaplasia or dysplastic changes. Despite the overall low incidence of clinically relevant manifestations reported in the literature, HGMPE is a clinically significant entity but further researches are required to better understand its clinical significance.
Gender preference and implications for screening colonoscopy: Impact of endoscopy nurses
Vui Heng Chong
World Journal of Gastroenterology , 2012, DOI: 10.3748/wjg.v18.i27.3590
Abstract: AIM: To assess the gender preferences, specifically the gender of the nursing staff (endoscopy assistants) and the impact on acceptance for screening colonoscopy (SC). METHODS: Patients or relatives attending the clinics or health care workers working in a tertiary center were invited to participate in this questionnaire study. The questionnaire enquired on the general demographics (1) age, gender, ethnicity, education level, and employment status, previous history of colonoscopy, family or personal history of colonic pathologies, personal and family history of any cancers; (2) subjects were asked if they would go for an SC if they had appropriate indications (age over 50 years, family history of colorectal cancer (CRC), fecal occult blood positive, anemia especially iron deficiency anemia, bleeding per rectum with or without loss of appetite, weight loss and abdominal pain) with and without symptoms attributable to CRC; and (3) preferences for the gender of the endoscopists and assistants and whether they would still undergo SC even if their preferences were not met. RESULTS: Eighty-four point seven percent (470/550) completed questionnaire were analysed. More female subjects expressed gender preferences for the endoscopists [overall 70%; female (67.7%) and male (2.3%)] compared to male subjects [overall 62.8%; male (56%) and female (6.8%), P = 0.102]. Similarly, more female subjects expressed gender preferences for the assistants [overall 74.5%; female (73.4%) and male (1.1%)] compared to male subjects [overall 58%, male (49.3%) and female (8.7%), P < 0.001]. Overall, a third would decline an SC, despite having appropriate indications, if their preferences were not met. On univariate analysis, male gender, non-Malay ethnicity (Chinese and others) and previous colonoscopy experience were more likely to undergo an SC, even if their preferences were not met (all P < 0.05). Gender and previous experience [odds ratio (OR) 1.68, 95% confidence interval (CI) 1.00-2.82, P < 0.05] with colonoscopy (OR 4.70, 95% CI 1.41-15.66, P < 0.05) remained significant on multivariate analysis. CONCLUSION: Genders preference for the endoscopy nurses/assistants is more common than for the endoscopist among women and has implications for the success of a screening colonoscopy program.
The Third National Writing Workshop: 10th to 12th May 2012.
Vui Heng CHONG
Brunei International Medical Journal , 2012,
Abstract: The Third National Writing Workshop that was jointly organised by the Clinical Research Unit, Raja Isteri Pengiran Anak Saleha Hospital and the Asia Pacific Association of Medical Editors (APAME) washeld in the Health Promotion Centre (HPC) Ministry of Health from the 10th to 12th May 2012. This workshop brought back the two professors (Prof. Wilfred Peh Chin Guan and Prof. Jose Lapena) who were involved the previous year’s workshop. The other faculty members included doctors from the Ministry of Health and lecturer from the Pengiran Anak Puteri Rasidah Sa’adatul Bolkiah (PAPRSB) Institute of Health Science, Universiti of Brunei Darussalam.
Spectrum of endoscopic findings among patients referred for colonoscopy in RIPAS Hospital.
Vui Heng CHONG,Steven TAN,Anand JALIHAL
Brunei International Medical Journal , 2012,
Abstract: Introduction: Colonoscopy is an investigation for the evaluation of lower gastrointestinal symptoms. Just like any other conditions, it is important to be aware of the spectrum of findings so that appropriate referral and decisions can be made. Materials and Methods: Patients (mean age 52.3 ± 15.3 years old with almost equal proportion of genders) referred for colonoscopy in RIPAS Hospital over a five year period (January 2003 to December 2007) were retrospectively identified and studied. Results: The most common indication for colonoscopy was bleeding per rectum (22.9%), followed by evaluation of abdominal pain (18.6%), anaemia (11.7%), colorectal cancer screening (11.7%), evaluation of constipation (5.9%) and altered bowel habits (3.8%). A large proportion (58.4%) colonoscopy was normal. The most common positive finding was haemorrhoids (30.3%), majority of which were categorised as grade I. This was followed by colonic polyps (17.6%), diverticular disease (12.1%), non-specific colitis (4.0%), colorectal cancers (4.0%) and ulcers (3.6%), melanosis coli (0.4%) and telangiectasia (0.1%). Colorectal cancer was most common among the Malays (4.4%), followed by the Chinese (4.0%), the indigenous (2.8) and the others (1.2%). Conclusions: Our study showed that the most common indication was for the evaluation of bleeding per rectum. Majority had normal colonoscopy and the most common positive finding was haemorrhoids. Importantly colorectal neoplasms accounted for one fifth of procedures with colorectal cancers accounting for four percent.
On the volume and the number of lattice of some semialgebraic sets
Ha Huy Vui,Tran Gia Loc
Mathematics , 2015,
Abstract: Let $f = (f_1,\ldots,f_m) : \R^n \longrightarrow \R^m$ be a polynomial map; $G^f(r) = \{x\in\R^n : |f_i(x)| \leq r,\ i =1,\ldots, m\}$. We show that if $f$ satisfies the Mikhailov - Gindikin condition then \begin{itemize} \item[(i)] $\text{Volume}\ G^f(r) \asymp r^\theta (\ln r)^k$ \item[(ii)] $\text{Card}\left(G^f(r) \cap \overset{o}{\ \Z^n}\right) \asymp r^{\theta'}(\ln r)^{k'}$, as $r\to \infty$, \end{itemize} where the exponents $\theta,\ k,\ \theta',\ k'$ are determined explicitly in terms of the Newton polyhedra of $f$. \\ \indent Moreover, the polynomial maps satisfy the Mikhailov - Gindikin condition form an open subset of the set of polynomial maps having the same Newton polyhedron.
Comparisons of VAR Model and Models Created by Genetic Programming in Consumer Price Index Prediction in Vietnam  [PDF]
Pham Van Khanh
Open Journal of Statistics (OJS) , 2012, DOI: 10.4236/ojs.2012.23029
Abstract: In this paper, we present an application of Genetic Programming (GP) to Vietnamese CPI in?ation one-step prediction problem. This is a new approach in building a good forecasting model, and then applying inflation forecasts in Vietnam in current stage. The study introduces the within-sample and the out-of-samples one-step-ahead forecast errors which have positive correlation and approximate to a linear function with positive slope in prediction models by GP. We also build Vector Autoregression (VAR) model to forecast CPI in quaterly data and compare with the models created by GP. The experimental results show that the Genetic Programming can produce the prediction models having better accuracy than Vector Autoregression models. We have no relavant variables (m2, ex) of monthly data in the VAR model, so no prediction results exist to compare with models created by GP and we just forecast CPI basing on models of GP with previous data of CPI.
Optimal Stopping Time for Holding an Asset  [PDF]
Pham Van Khanh
American Journal of Operations Research (AJOR) , 2012, DOI: 10.4236/ajor.2012.24062
Abstract: In this paper, we consider the problem to determine the optimal time to sell an asset that its price conforms to the Black-Schole model but its drift is a discrete random variable taking one of two given values and this probability distribution behavior changes chronologically. The result of finding the optimal strategy to sell the asset is the first time asset price falling into deterministic time-dependent boundary. Moreover, the boundary is represented by an increasing and continuous monotone function satisfying a nonlinear integral equation. We also conduct to find the empirical optimization boundary and simulate the asset price process.
Clinical Implementation of a 3D Dosimeter for Accurate IMRT and VMAT Patient Specific QA  [PDF]
Thuc Pham, Jianjie Luo
Open Journal of Biophysics (OJBIPHY) , 2013, DOI: 10.4236/ojbiphy.2013.31A013
Abstract:

The Delta4 3D dose verification device was commissioned in the current work for pre-treatment quality assurance (QA) of Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) plans. The cross calibration and relative array calibration were performed to enable absolute dose comparison. The linearity of response with dose and temperature sensitivity tests were also conducted to investigate dosimetric properties of the Delta4 device. The need to modify the original CT image of the Delta4 phantom for accurate dose calculation and comparison is addressed in this work, applying a CT extension algorithm. A number of test plans varying from simple 4—field conformal to IMRT and VMAT plans were measured to evaluate the accuracy of this device. It was found that the Delta4 device measured dose accurately to within ±1%. In order to maintain this level of accuracy the machine output fluctuations need to be corrected prior to each measurement and the relative array calibration needs to be performed every six months.

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