Nguyen Dung - Academia.edu (original) (raw)

Papers by Nguyen Dung

We give an estimate of the first eigenvalue of the Laplace operator on a complete noncompact stab... more We give an estimate of the first eigenvalue of the Laplace operator on a complete noncompact stable minimal hypersurface MMM in a complete simply connected Riemannian manifold with pinched negative sectional curvature. In the same ambient space, we prove that if a complete minimal hypersurface MMM has sufficiently small total scalar curvature then MMM has only one end. We also obtain a vanishing theorem for L2L^2L2 harmonic 1-forms on minimal hypersurfaces in a Riemannian manifold with sectional curvature bounded below by a negative constant. Moreover we provide sufficient conditions for a minimal hypersurface in a Riemannian manifold with nonpositive sectional curvature to be stable.

Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association, 2008

In the present study, the essential oil isolated from the buds of Cleistocalyx operculatus by hyd... more In the present study, the essential oil isolated from the buds of Cleistocalyx operculatus by hydrodistillation was analyzed by GC and GC/MS. A total of 55 compounds representing 93.71% of the oil were identified. The oil significantly inhibited the growth of food spoilage (FS), food-borne (FB), skin pathogens (SP), methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococci (VRE) and multiantibiotic-resistant bacteria (MARB). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the oil against the tested microorganisms were found in the range of 1-20muL/mL. Whereas the ethanol extract exhibited potential antibacterial activity against the entire tested Gram positive bacteria and one food spoilage Gram negative bacterium P. aeruginosa. The MIC and MBC values of ethanol extract against the tested bacteria were found in the range of 0.25-32mg/mL. The scanning electron microscopic (SEM) studies demonstrated potential detrimental effect of the essential oil on the morphology of MRSA-P249 and VRE-B2332 at the used MIC values, along with the potential effect on cell viabilities of the tested bacteria. Moreover, the total antioxidant capacity and the scavenging effect on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals of the essential oil and the ethanol extract were also evaluated.

Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association, 2009

Cleistocalyx operculatus (Roxb.) Merr and Perry buds (Myrtaceae) are widely used in folk medicine... more Cleistocalyx operculatus (Roxb.) Merr and Perry buds (Myrtaceae) are widely used in folk medicine for the treatment of gastric ailments as well as an antiseptic agent in China, Vietnam and some other tropical countries. However, to be clinically useful, more scientific data are needed. In the present study, we investigated the in vitro and in vivo anti-inflammatory activities of the essential oil of the C. operculatus buds (EO-CO). In the applied tests, EO-CO significantly inhibited lipopolysaccharide (LPS)-induced secretion of pro-inflammatory cytokines, including tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta), in RAW 264.7 cells, a mouse macrophage-like cell line. Also the mRNA expression of TNF-alpha and IL-1beta was suppressed by treatment with EO-CO in LPS-stimulated RAW 264.7 cells. Moreover, reporter gene analysis revealed that the EO-CO significantly blocked LPS-induced transcriptional activation of NF-kappaB in RAW 264.7 cells. Nuclear translocation of p65 subunit was also suppressed by EO-CO treatment. In addition, EO-CO inhibited phorbol ester-induced increase in ear swelling and skin water content in BALB/c mice. These results suggest that EO-CO might exert an anti-inflammatory effect by suppressing the expression of pro-inflammatory cytokines which is mediated, at least in part, by blocking NF-kappaB activation.

Proteomics insights, 2012

Serum and membrane proteins are two of the most attractive targets for proteomic analysis. Previo... more Serum and membrane proteins are two of the most attractive targets for proteomic analysis. Previous membrane protein studies tend to focus on tissue sample, while membrane protein studies in serum are still limited. In this study, an analysis of membrane proteins in normal human serum was carried out. Nano-liquid chromatography-electrospray ionization mass spectrometry (NanoLC-ESI-MS/MS) and bioinformatics tools were used to identify membrane proteins. Two hundred and seventeen membrane proteins were detected in the human serum, of which 129 membrane proteins have at least one transmembrane domain (TMD). Further characterizations of identified membrane proteins including their subcellular distributions, molecular weights, post translational modifications, transmembrane domains and average of hydrophobicity, were also implemented. Our results showed the potential of membrane proteins in serum for diagnosis and treatment of diseases.

Bulletin of The Chemical Society of Japan, 1997

Analytical Sciences, 1994

The photocatalytic oxidation of Reactive Blue 2 (RB2), an anthraquinone dye with triazine reactiv... more The photocatalytic oxidation of Reactive Blue 2 (RB2), an anthraquinone dye with triazine reactive group was investigated using P25 Degussa as catalyst and UV- light in aqueous solution. The photooxidation of RB2 has been studied at different pH values. The kinetics of RB2 disapperance follows first-order and the constant colourization rate is fastest at pH = 10. The mineralization of RB2 and the evolutions of intermediates products were performed until 30 hours. RB2 was completely oxidated with a mineralization of organic carbon into CO2. Heteroatoms were released into innocuous diluted inorganic final products such as sulfate and nitrate ions. The kinetics of TOC had have two stages corresponding to the decolourization and the mineralization. The triazine ring was converted into cyanuric acid.

Fuel and Energy Abstracts, 2011

It is a fact that in Viet Nam, Muscovy ducks are raised in large populations (approximately 8 mil... more It is a fact that in Viet Nam, Muscovy ducks are raised in large populations (approximately 8 million), usually kept in small flocks together with mallards and chickens. As a result, it is a great concern for epidemiologists to elucidate possible differences in relation to these species being exposed to infection with H5N1. To do this, an experimental study on infections with different genotypes of H5N1 in mallards and Muscovy ducks have been conducted, where it was found that the mortality of the inoculated Muscovy ducks was at least 80%, regardless of the virus strain employed. In contrast, the mortality of the mallards ranged from nil to 100%, which suggests that Muscovy ducks are more susceptible to HPAIV H5N1 infection in terms of disease development and mortality. It was also found that higher virus titers developed in vital organs of Muscovy ducks compared to mallards, particularly in the brain. Due to their high susceptibility, it is unlikely that Muscovy ducks act as a silent reservoir. The virus strains used in this study, to a certain degree, differed in their virulence properties to the bird species in question.

Journal of infection and chemotherapy : official journal of the Japan Society of Chemotherapy, 2014

The use of tenofovir has been rapidly increasing in Vietnam. Several studies identified low body ... more The use of tenofovir has been rapidly increasing in Vietnam. Several studies identified low body weight as a risk factor for tenofovir-induced nephrotoxicity. However, little is known about the impact of tenofovir on renal function in HIV-infected Vietnamese with generally low weight. An observational single-center cohort of adult HIV-infected patients on antiretroviral therapy at National Hospital of Tropical Diseases, Hanoi. Patients on tenofovir or with creatinine clearance ≤60 ml/min at baseline were excluded. The incidence of renal dysfunction was compared between patients who switched to tenofovir and those who did not. Renal dysfunction was defined as 25% decline of creatinine clearance from baseline. Time to renal dysfunction was analyzed by the Kaplan-Meier method between the two groups. The Cox hazard model was used to determine risk factors for renal dysfunction in uni- and multivariate analyses. Of 556 patients enrolled in this study, 403 were non-tenofovir group while 153 were the tenofovir-switched group. Renal dysfunction occurred at a higher rate in the tenofovir-switched group (92.5 per 1000 person-years) than the non-tenofovir group (47.8 per 1000 person-years)(p = 0.023, Log-rank test). Multivariate analysis confirmed that tenofovir use, low body weight and glucosuria were significant risk factors for renal dysfunction (hazard ratio = 1.980; 95% confidential interval, 1.094-3.582, HR = 1.057; 95%CI, 1.016-1.098, HR = 5.202; 95%CI, 1.245-21.738, respectively). Tenofovir use, low body weight and glucosuria were significant risk factors for renal dysfunction. We suggest close monitoring of renal function in patients with these risk factors even in resource-limited setting.

Taiwanese Journal of Mathematics, 2013

Taiwanese Journal of Mathematics, 2014

Communications in Physics, 2012

The 2012 International Conference on Advanced Technologies for Communications, 2012

ABSTRACT Deployment of wireless sensor networks always faces the issue of energy limitation. With... more ABSTRACT Deployment of wireless sensor networks always faces the issue of energy limitation. Without appropriate control policy, data messages might be routed over already-exhausted routes, quickly disrupting network connectivity. If a node transmits data at an excessively high power level, it not only depletes its own energy budget wastefully, but also interferes in other parallel transmissions. In this study, we introduce a cooperative power control strategy in which nodes of routes jointly tune their transmit power regularly over time and upon route setup. Tuning is made under hints of surrounding nodes. Routes are selected based on link metrics that is a function of signal strength, remaining energy, and path loss. To keep balancing power consumption among nodes, energy-aware established routes are considered re-routing periodically. Transmit power of each node is set at a level is just high enough under the hint of its adjacent downstream node. Simulation outputs do demonstrate the soundness of our proposals with respect to connectivity and throughput.

Computer Methods in Applied Mechanics and Engineering, 2008

A finite element formulation is presented for modelling geometrically nonlinear thin shells which... more A finite element formulation is presented for modelling geometrically nonlinear thin shells which exploits standard Lagrange finite element basis functions without introducing rotation degrees of freedom. The classical regularity requirements associated with thin bending problems are circumvented by introducing special integrals over inter-element edges. The use of Lagrange finite element basis functions and the absence of rotation degrees of freedom make the formulation relatively simple, and discontinuities in material properties and non-smooth shell geometry can be incorporated trivially. The variational problem can be exactly linearised, leading to an efficient Newton–Raphson solution process. The performance of the approach is demonstrated via a range of numerical benchmarks for both geometrically linear and nonlinear problems. It is shown that cubic elements perform particularly well.

The known system of nonlinear differential equations (PDE) describing vortical motions of an idea... more The known system of nonlinear differential equations (PDE) describing vortical motions of an ideal electron-ion plasma with viscosity in the presence of a slightly inhomogeneous magnetic field is reduced to a Lorentz type system of 3 ordinary differential equations (ODE). The numerical solution of this system, with a set of values for real plasma physical parameters, shows the occurrence of a state with strange attractors. This means that the beginning of the vortices' formation is essentially a nonlinearity effect.

International Journal of Low Radiation, 2009

... Dose response of polyvinyl alcohol films dyed by methyl red under gamma irradiation Nguyen Tr... more ... Dose response of polyvinyl alcohol films dyed by methyl red under gamma irradiation Nguyen Trieu Tu and Nguyen Van Dung ... Nguyen Van Dung is an MSc in Physics at the College of Sciences, Hanoi National University, Vietnam. ...

Topology and its Applications, 2013

Radiation Physics and Chemistry, 1995

rhe acrylamide was grattrd by radiatlon onto starth which is a kind polymeric biomaterial.The ure... more rhe acrylamide was grattrd by radiatlon onto starth which is a kind polymeric biomaterial.The urease was immobilized on the grattrd stnrc h.Somr experiments to observe the quantitative relationshlps between the percent gratt and th(l nc-tivily of immobilized enzyme were determined.The enzyme ac-tivlty was maintained by morc2 thdn sclvrn batch enzyme reactions.