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Search Results: 1 - 10 of 195368 matches for " Uyen D Nguyen "
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Thermal modeling of lesion growth with radiofrequency ablation devices
Isaac A Chang, Uyen D Nguyen
BioMedical Engineering OnLine , 2004, DOI: 10.1186/1475-925x-3-27
Abstract: We present an axisymmetric two-dimensional finite element model that calculates cell damage in tissues and compare lesion sizes using common tissue damage and iso-temperature contour definitions. The model accounts for both temperature-dependent changes in the electrical conductivity of tissue as well as tissue damage-dependent changes in local tissue perfusion. The data is validated using excised porcine liver tissues.The data demonstrate the size of thermal lesions is grossly overestimated when calculated using traditional temperature isocontours of 42°C and 47°C. The computational model results predicted lesion dimensions that were within 5% of the experimental measurements.When modeling radiofrequency ablation problems, temperature isotherms may not be representative of actual tissue damage patterns.The mitigation of primary and metastatic tumors by radiofrequency ablation is a developing research area. The goal of ablation is to necrose treatment volumes by raising the temperature of targeted tissues. Ablation probes are inserted percutaneously, laparoscopically, or during surgery into cancerous tumors. Once positioned, high frequency alternating current (450–550 kHz) is delivered through an uninsulated electrode into the surrounding tissues to a dispersive ground pad that is applied to the patient. The electromagnetic energy is converted to heat by resistive heating.While the usage of radiofrequency ablation devices is well established, efforts to optimize treatment strategies are ongoing. An important consideration in optimizing ablation is determining what treatment volumes are necessary and acceptable. In liver ablation, for example, treatment volumes generally extend a centimeter beyond the dimensions of a tumor [1-3]. Since the liver possesses regenerative characteristics, it is more critical to insure that necrosis is achieved in 100% of the cancerous cell volume than to minimize damage to healthy tissues. In contrast, a centimeter margin in cardiac abla
Reference Ranges for Bone Mineral Density and Prevalence of Osteoporosis in Vietnamese Men and Women
Lan T Ho-Pham, Uyen D T Nguyen, Hoa N Pham, Nguyen D Nguyen, Tuan V Nguyen
BMC Musculoskeletal Disorders , 2011, DOI: 10.1186/1471-2474-12-182
Abstract: This cross-sectional study involved 357 men and 870 women aged between 18 and 89 years, who were randomly sampled from various districts within Ho Chi Minh City, Vietnam. BMD at the femoral neck, lumbar spine and whole body was measured by DXA (Hologic QDR4500). Polynomial regression models and bootstraps method were used to determine peak BMD and standard deviation (SD). Based on the two parameters, we computed T-scores (denoted by TVN) for each individual in the study. A similar diagnosis was also done based on T-scores provided by the densitometer (TDXA), which is based on the US White population (NHANES III). We then compared the concordance between TVN and TDXA in the classification of osteoporosis. Osteoporosis was defined according to the World Health Organization criteria.In post-menopausal women, the prevalence of osteoporosis based on femoral neck TVN was 29%, but when the diagnosis was based on TDXA, the prevalence was 44%. In men aged 50+ years, the TVN-based prevalence of osteoporosis was 10%, which was lower than TDXA-based prevalence (30%). Among 177 women who were diagnosed with osteoporosis by TDXA, 35% were actually osteopenia by TVN. The kappa-statistic was 0.54 for women and 0.41 for men.These data suggest that the T-scores provided by the Hologic QDR4500 over-diagnosed osteoporosis in Vietnamese men and women. This over-diagnosis could lead to over-treatment and influence the decision of recruitment of participants in clinical trials.Osteoporosis and its consequence of fragility fracture represent a major public health problem not only in developed countries, but in developing countries as well [1]. The number of fractures in Asia is higher than that in European countries combined. Of all the fractures in the world, approximately 17% was found to occur in Southeast Asia, 29% in West Pacific, as compared to 35% occurring in Europe [2]. However, the prevalence of and risk factors for osteoporosis in Asian populations have not been well documented.
Survey Evaluating Sleep Education Catalyzed Change in Residency Training  [PDF]
Demetra S. Stamm, Sandra Taylor, Uyen Thao Nguyen, Kimberly Hardin
International Journal of Clinical Medicine (IJCM) , 2015, DOI: 10.4236/ijcm.2015.67058
Background: Despite the high prevalence and negative effects of sleep disorders, sleep issues often remain unexplored during medical encounters. Research has shown that primary care physicians regard their knowledge as inadequate. Objective: We investigated residents’ perceived adequacy of sleep education and level of competency in diagnosing and treating sleep disorders. Methods: A questionnaire via Survey Monkey was administered to senior residents in University of California, Davis (UCD) from family medicine, internal medicine, neurology, and psychiatry to assess perception of their knowledge and training of sleep disorders. Likert scale ratings were used, from 1 (not adequate/competent) to 5 (extremely adequate/competent). Non-parametric statistical methods were used to evaluate differences in survey responses among specialties and assess the correlation between survey responses. Results: Only 33 residents responded with a 29.5% response rate. Neurology residents routinely rotate with a sleep medicine attending and subsequently reported the highest self-competency, adequacy of training, hours of didactics received and frequency of asking patients about sleep. All other residents reported receiving insufficient sleep medicine education. The combined mean score was 1.5 across the specialties regarding adequacy of sleep education in their respective medical schools with 31.3% reporting no sleep medicine training. Conclusions: This study demonstrated that there is a perceived deficit in most residents’ training and competency regarding sleep disorders. These results prompted 2 of the 4 residency programs to change their educational structure with electives in clinical sleep medicine. We believe that this paper illuminates potential need for increasing sleep medicine education throughout various levels of training. Nationwide educational research is needed to promote ACGME to incorporate the fundamentals of sleep medicine into core curriculum. Current Knowledge/Study Rationale: There are no studies, to our knowledge, directly measuring residents’ perceived adequacy of sleep medicine education provided and their perceived level of competency in diagnosing and treating sleep disorders. The aim of this study was to evaluate both the amount of time and quality of sleep education provided to residents as insufficient knowledge in addressing sleep problems may reflect gaps in educational
Task Allocation Model for Rescue Disabled Persons in Disaster Area with Help of Volunteers
Kohei Arai,Tran Xuan Sang,Nguyen Thi Uyen
International Journal of Advanced Computer Sciences and Applications , 2012,
Abstract: In this paper, we present a task allocation model for search and rescue persons with disabilities in case of disaster. The multi agent-based simulation model is used to simulate the rescue process. Volunteers and disabled persons are modeled as agents, which each have their own attributes and behaviors. The task of volunteers is to help disabled persons in emergency situations. This task allocation problem is solved by using combinatorial auction mechanism to decide which volunteers should help which disabled persons. The disaster space, road network, and rescue process are also described in detail. The RoboCup Rescue simulation platform is used to present proposed model with different scenarios.
A Prospective Study of the Causes of Febrile Illness Requiring Hospitalization in Children in Cambodia
Kheng Chheng, Michael J. Carter, Kate Emary, Ngoun Chanpheaktra, Catrin E. Moore, Nicole Stoesser, Hor Putchhat, Soeng Sona, Sin Reaksmey, Paul Kitsutani, Borann Sar, H. Rogier van Doorn, Nguyen Hanh Uyen, Le Van Tan, Daniel Paris, Stuart D. Blacksell, Premjit Amornchai, Vanaporn Wuthiekanun, Christopher M. Parry, Nicholas P. J. Day, Varun Kumar
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0060634
Abstract: Background Febrile illnesses are pre-eminent contributors to morbidity and mortality among children in South-East Asia but the causes are poorly understood. We determined the causes of fever in children hospitalised in Siem Reap province, Cambodia. Methods and Findings A one-year prospective study of febrile children admitted to Angkor Hospital for Children, Siem Reap. Demographic, clinical, laboratory and outcome data were comprehensively analysed. Between October 12th 2009 and October 12th 2010 there were 1225 episodes of febrile illness in 1180 children. Median (IQR) age was 2.0 (0.8–6.4) years, with 850 (69%) episodes in children <5 years. Common microbiological diagnoses were dengue virus (16.2%), scrub typhus (7.8%), and Japanese encephalitis virus (5.8%). 76 (6.3%) episodes had culture-proven bloodstream infection, including Salmonella enterica serovar Typhi (22 isolates, 1.8%), Streptococcus pneumoniae (13, 1.1%), Escherichia coli (8, 0.7%), Haemophilus influenzae (7, 0.6%), Staphylococcus aureus (6, 0.5%) and Burkholderia pseudomallei (6, 0.5%). There were 69 deaths (5.6%), including those due to clinically diagnosed pneumonia (19), dengue virus (5), and melioidosis (4). 10 of 69 (14.5%) deaths were associated with culture-proven bloodstream infection in logistic regression analyses (odds ratio for mortality 3.4, 95% CI 1.6–6.9). Antimicrobial resistance was prevalent, particularly in S. enterica Typhi, (where 90% of isolates were resistant to ciprofloxacin, and 86% were multi-drug resistant). Comorbid undernutrition was present in 44% of episodes and a major risk factor for acute mortality (OR 2.1, 95% CI 1.1–4.2), as were HIV infection and cardiac disease. Conclusion We identified a microbiological cause of fever in almost 50% of episodes in this large study of community-acquired febrile illness in hospitalized children in Cambodia. The range of pathogens, antimicrobial susceptibility, and co-morbidities associated with mortality described will be of use in the development of rational guidelines for infectious disease treatment and control in Cambodia and South-East Asia.
Elevated Adiponectin Serum Levels in Women with Systemic Autoimmune Diseases
éric Toussirot,Béatrice Gaugler,Malika Bouhaddi,Nhu Uyen Nguyen,Philippe Saas,Gilles Dumoulin
Mediators of Inflammation , 2010, DOI: 10.1155/2010/938408
Abstract: Adipose tissue produces a wide range of proteins that may influence the immune system. In this study, we assessed the serum levels of leptin, adiponectin, and ghrelin, in association with the measurements of body composition, in 15 female patients with various autoimmune diseases (systemic lupus erythematosus, primary Sj?gren's syndrome, sarcoidosis, mixed connective tissue disease, vasculitis, CREST syndrome, and polymyositis) and in 15 healthy female controls. There were no statistically significant differences between the patients and controls with regard to serum leptin, serum ghrelin, global fat mass, adiposity, and fat mass in the android or gynoid regions, whereas serum adiponectin levels were higher in patients than controls ( ?μg/mL versus ?μg/mL; ). As adiponectin is known to exhibit potent anti-inflammatory properties, a high adiponectinemia in patients with systemic autoimmune disease may mitigate the inflammatory response. However, the precise consequences of these elevated serum adiponectin levels on the metabolic syndrome development and atherosclerotic cardiovascular risk in this patient population still needs to be determined. 1. Introduction It is now well established that the adipose tissue, and more precisely the white adipose tissue, is not only a storage organ but plays an active role in that it can produce and release various mediators that might play a role in the physiological processes [1, 2]. Indeed, adipocytes produce specific proteins or adipokines with a broad range of biological and physiological activities related to glucose homeostasis, lipid metabolism, appetite regulation, angiogenesis, hemostasis, and reproduction as well as immunity. Adipose tissue is composed of different cellular types, of which the adipocytes are the most abundant, but it also contains macrophages. These macrophages can release various cytokines including TNFα and IL-6 [1–3]. In obese patients, a low-grade systemic inflammation has been reported [1], as shown by increased CRP and IL-6 levels compared to those observed in lean subjects. This relationship between fat tissue and systemic inflammation reflects the adipose tissue’s potential contribution with regard to the inflammatory response, which may be partly explained by the production of inflammatory cytokines. In fact, macrophages from adipose tissue have been shown to contribute to up to 30% of circulating IL-6, indicating that adipose tissue is a significant production site of circulating proinflammatory cytokines [1, 2]. The main adipokines studied were leptin and adiponectin. Leptin’s role
Estimating Riparian and Agricultural Actual Evapotranspiration by Reference Evapotranspiration and MODIS Enhanced Vegetation Index
Pamela L. Nagler,Edward P. Glenn,Uyen Nguyen,Russell L. Scott,Tanya Doody
Remote Sensing , 2013, DOI: 10.3390/rs5083849
Abstract: Dryland river basins frequently support both irrigated agriculture and riparian vegetation and remote sensing methods are needed to monitor water use by both crops and natural vegetation in irrigation districts. We developed an algorithm for estimating actual evapotranspiration (ET a) based on the Enhanced Vegetation Index (EVI) from the Moderate Resolution Imaging Spectrometer (MODIS) sensor on the EOS-1 Terra satellite and locally-derived measurements of reference crop ET (ET o). The algorithm was calibrated with five years of ET a data from three eddy covariance flux towers set in riparian plant associations on the upper San Pedro River, Arizona, supplemented with ET a data for alfalfa and cotton from the literature. The algorithm was based on an equation of the form ET a = ET o [a(1 ? e ?bEVI) ? c], where the term (1 ? e ?bEVI) is derived from the Beer-Lambert Law to express light absorption by a canopy, with EVI replacing leaf area index as an estimate of the density of light-absorbing units. The resulting algorithm capably predicted ET a across riparian plants and crops (r 2 = 0.73). It was then tested against water balance data for five irrigation districts and flux tower data for two riparian zones for which season-long or multi-year ET a data were available. Predictions were within 10% of measured results in each case, with a non-significant (P = 0.89) difference between mean measured and modeled ET a of 5.4% over all validation sites. Validation and calibration data sets were combined to present a final predictive equation for application across crops and riparian plant associations for monitoring individual irrigation districts or for conducting global water use assessments of mixed agricultural and riparian biomes.
Response of Spectral Reflectances and Vegetation Indices on Varying Juniper Cone Densities
Dailiang Peng,Zhangyan Jiang,Alfredo R. Huete,Guillermo E. Ponce-Campos,Uyen Nguyen,Jeffrey C. Luvall
Remote Sensing , 2013, DOI: 10.3390/rs5105330
Abstract: Juniper trees are widely distributed throughout the world and are common sources of allergies when microscopic pollen grains are transported by wind and inhaled. In this study, we investigated the spectral influences of pollen-discharging male juniper cones within a juniper canopy. This was done through a controlled outdoor experiment involving ASD FieldSpec Pro Spectroradiometer measurements over juniper canopies of varying cone densities. Broadband and narrowband spectral reflectance and vegetation index (VI) patterns were evaluated as to their sensitivity and their ability to discriminate the presence of cones. The overall aim of this research was to assess remotely sensed phenological capabilities to detect pollen-bearing juniper trees for public health applications. A general decrease in reflectance values with increasing juniper cone density was found, particularly in the Green (545–565 nm) and NIR (750–1,350 nm) regions. In contrast, reflectances in the shortwave-infrared (SWIR, 2,000 nm to 2,350 nm) region decreased from no cone presence to intermediate amounts (90 g/m 2) and then increased from intermediate levels to the highest cone densities (200 g/m 2). Reflectance patterns in the Red (620–700 nm) were more complex due to shifting contrast patterns in absorptance between cones and juniper foliage, where juniper foliage is more absorbing than cones only within the intense narrowband region of maximum chlorophyll absorption near 680 nm. Overall, narrowband reflectances were more sensitive to cone density changes than the equivalent MODIS broadbands. In all VIs analyzed, there were significant relationships with cone density levels, particularly with the narrowband versions and the two-band vegetation index (TBVI) based on Green and Red bands, a promising outcome for the use of phenocams in juniper phenology trait studies. These results indicate that spectral indices are sensitive to certain juniper phenologic traits that can potentially be used for juniper cone detection in support of public health applications.
Statistical Classification Using the Maximum Function  [PDF]
T. Pham-Gia, Nguyen D. Nhat, Nguyen V. Phong
Open Journal of Statistics (OJS) , 2015, DOI: 10.4236/ojs.2015.57068
Abstract: The maximum of k numerical functions defined on \"\", \"\", by \"\", \"\"??is used here in Statistical classification. Previously, it has been used in Statistical Discrimination [1] and in Clustering [2]. We present first some theoretical results on this function, and then its application in classification using a computer program we have developed. This approach leads to clear decisions, even in cases where the extension to several classes of Fisher’s linear discriminant function fails to be effective.
The Relationship between Obligation to Parents and Life Satisfaction for Vietnamese American Adults
Chau Nguyen,Tuyen D. Nguyen
Asian Social Science , 2012, DOI: 10.5539/ass.v8n6p11
Abstract: This paper presents an analysis employing the quantitative research method to study Vietnamese adult children’s obligation to parents. Using primary data gathered from 95 Vietnamese American adults, this study examines the relationship between obligation to parents and life satisfaction of Vietnamese American adults. The findings indicate that obligations to parents have been adapted among the Vietnamese American adults in the sample. Different patterns of change in obligation to parents among the Vietnamese American adults are recognized. Vietnamese American adults are experiencing social, economic, and cultural challenges associated with a new life in the United States but they are struggling in ways that did not significantly alter their traditional familial obligations. The findings also demonstrate a very high level of satisfaction for the sampled Vietnamese Americans who have been Acculturalized/Americanized for about fifteen years.
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