Vietnam Academy of Science and Technology
Hanoi, Vietnam

The Vietnam Academy of Science and Technology is a large national university in Vietnam. It was founded in 1975 as the Vietnam Academy of Science, and renamed the Vietnam Academy of Science and Technology in 2008. Its infrastructure spans Hanoi, Ho Chi Minh City, Hai Phong, Nha Trang, Da Lat, and Huế.In March 2010, the Vietnam Academy of Science and Technology launched a peer reviewed open access journal Advances in Natural science: Nanoscience and Nanotechnology . The journal is jointly published with IOP Publishing. Wikipedia.

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Thinh P.D.,Vietnam Academy of Science and Technology
Marine drugs | Year: 2013

Three different fucoidan fractions were isolated and purified from the brown alga, Sargassum mcclurei. The SmF1 and SmF2 fucoidans are sulfated heteropolysaccharides that contain fucose, galactose, mannose, xylose and glucose. The SmF3 fucoidan is highly sulfated (35%) galactofucan, and the main chain of the polysaccharide contains a →3)-α-L-Fucp(2,4SO3 -)-(1→3)-α-L-Fucp(2,4SO3 -)-(1→ motif with 1,4-linked 3-sulfated α-L-Fucp inserts and 6-linked galactose on reducing end. Possible branching points include the 1,2,6- or 1,3,6-linked galactose and/or 1,3,4-linked fucose residues that could be glycosylated with terminal β-D-Galp residues or chains of alternating sulfated 1,3-linked α-L-Fucp and 1,4-linked β-D-Galp residues, which have been identified in galactofucans for the first time. Both α-L-Fucp and β-D-Galp residues are sulfated at C-2 and/or C-4 (and some C-6 of β-D-Galp) and potentially the C-3 of terminal β-D-Galp, 1,4-linked β-D-Galp and 1,4-linked α-L-Fucp residues. All fucoidans fractions were less cytotoxic and displayed colony formation inhibition in colon cancer DLD-1 cells. Therefore, these fucoidan fractions are potential antitumor agents.

News Article | January 13, 2016

Digging foundations for temples or schools, harvesting rice in paddy fields: these are some of the ways that the decaying remains of Vietnam War victims still turn up, 40 years after the conflict ended. Now an effort has begun that will use smart DNA technologies to identify the bones of the half a million or more Vietnamese soldiers and civilians who are thought still to be missing. It is the largest ever systematic identification effort; only the identification of more than 20,000 victims of armed conflicts in Bosnia and Herzegovina during the 1990s comes close. “When I was a 21-year-old in the medical corps there, I never imagined that such a project could ever become possible,” says Vietnam veteran and genomics pioneer Craig Venter, head of the J. Craig Venter Institute in La Jolla, California. “We thought of body counts as statistics — now, decades later, it may be possible to put names to them.” Although the United States has repatriated and identified most of its war dead, Vietnam has so far identified just a few hundred people, using outdated techniques. Yet people in Vietnam remain desperate to acquire the remains of family members. A few years ago, the government responded to their plight and asked the Advanced International Joint Stock Company (AIC) in Hanoi to investigate how best to proceed. The AIC consulted medical-diagnostics company Bioglobe in Hamburg, Germany, on how to equip the Vietnamese labs and train their scientists. In 2014, the Vietnamese government announced an investment of 500 billion dong (US$25 million) in the project and said that it would upgrade its three existing DNA-testing centres. This was great news, says Truong Nam Hai, head of the Institute of Biotechnology at the Vietnam Academy of Science and Technology, which hosts the first DNA-testing laboratory to be upgraded. In the 1990s, his institute proposed plans for identifying the missing, he says. However, “due to difficult circumstances at the time”, these did not take off. Last month, the government signed a training and consultancy contract with Bioglobe, which will allow the sequencing effort to start. “The technical challenges are considerable but tractable,” says Bioglobe’s chief executive, Wolfgang Höppner, who crafted the proposal for Vietnam. In the country’s hot and humid climate, DNA in bones that have lain in shallow graves for decades is likely to have degraded extensively. Moreover, contaminants from soil microbes can inhibit the enzymes that scientists use to amplify what little DNA remains to levels that can be analysed. And because of the large numbers of bones involved, the work needs to be done efficiently, adds Höppner. Höppner’s proposal makes use of kits from Germany-based biotech company Qiagen, which have been designed to protect and reveal as much DNA as possible when dealing with difficult sources such as old, buried bones, and are also amenable to automated, ‘high throughput’ processes. The identification process involves powdering bone samples and chemically breaking down their cells. Before amplification, the DNA is extracted in sealed Qiagen cartridges that contain chemicals to wash away substances that could inhibit the process. Another Qiagen kit then checks the amplified DNA against a large set of genomic markers to create a DNA profile of the sample. The kit can also detect whether inhibitors are still present. In cases in which inhibitors prove stubborn, samples will be analysed manually by slower, more complex methods that have been optimized by an experienced forensic laboratory run by the International Commission on Missing Persons (ICMP). That lab, in Bosnia and Herzegovina’s capital Sarajevo, led the effort to identify people killed during the 1990s conflict, including nearly all of the 8,000 or so who were massacred in 1995 in Srebrenica. The ICMP will also have a role in training Vietnamese scientists. Truong’s lab will next month send six scientists on a three-month programme. They will spend most of their time in Hamburg focusing on DNA tests, but they will also have a stint at the ICMP to learn other critical aspects of identification: how to avoid jumbling bones from different skeletons when exhuming them from mass graves, or how to look for clues in bones that might aid identification, such as pointers to height or gender. It was possible to extract useful levels of DNA from around 80% of the bones from the Srebrenica victims, says Thomas Parsons, head of the ICMP lab. The Vietnamese bones have been in the ground for longer and in a more damaging climate, but highly optimized methods and careful selection of skeletal samples will help, he says. The Vietnam project will also need reference DNA from family members to compare with the bone DNA from victims. It plans to have an outreach programme calling for people to donate saliva samples to create a reference data bank — but this will not be easy. Many war victims may have died too young to have had children, and their parents may also be dead, so reference samples will have to come from more distant relatives whose DNA is less similar. “That is why it is particularly important to do the DNA analysis with a larger than normal set of markers,” says Höppner. The outreach programme will also call for people to come forward with information on where bones might be buried. Unlike in Bosnia, where investigators could in some cases use satellite imagery to identify mass graves, the Vietnamese effort will rely on witness reports, as well as on common and military knowledge. Once all three government DNA-testing centres are upgraded, probably by 2017, they will together be able to identify between 8,000 and 10,000 people a year, says Truong. He also anticipates that the DNA project will improve Vietnam’s scientific culture.

Phat V.N.,Vietnam Academy of Science and Technology
Journal of the Franklin Institute | Year: 2010

This paper deals with the problem of stabilization for a class of hybrid systems with time-varying delays. The system to be considered is with nonlinear perturbation and the delay is time varying in both the state and control. Using an improved Lyapunov-Krasovskii functional combined with Newton-Leibniz formula, a memoryless switched controller design for exponential stabilization of switched systems is proposed. The conditions for the exponential stabilization are presented in terms of the solution of matrix Riccati equations, which allow for an arbitrary prescribed stability degree. © 2009 The Franklin Institute.

Nguyen K.V.,Vietnam Academy of Science and Technology
Engineering Structures | Year: 2013

In this paper, based on the comparison between open and breathing crack detections of a vehicle-bridge system subjected to a moving vehicle, a wavelet spectrum technique for detection of breathing crack phenomenon is presented. The stiffness of element with an open crack is calculated from fracture mechanics and the stiffness of element with a breathing crack is modeled as a time dependent stiffness matrix using the stiffness of the element with an open crack. When there is a breathing crack, the stiffness matrix of the structure at each moment depends on the curvature of the structure at the crack position. The simulation results show that when the crack "breaths" the amplitude of the vibration of the beam is smaller than in the case of an open crack. This is a warning for crack detection by using the amplitude of the dynamic response when there is a breathing crack in the structure. The open and breathing cracks can be distinguished by monitoring the instantaneous frequency (IF) of the system using the wavelet spectrum. While the IF in the case of open cracks remains unchanged during vibration, it is varying when there is a presence of breathing cracks. It is interesting that peaks in the wavelet transform of the response used to determine crack positions in case of breathing crack(s) are much larger in comparison with the case of open crack(s). The cracks can be detected with a noise level up to 10% for the case of breathing cracks while it is only 5% for the case of open cracks [28]. These imply that the wavelet-based method for crack detection is much more efficient when breathing crack(s) are present in comparison with the case of open crack(s). © 2013 Elsevier Ltd.

Nguyen K.,Vietnam Academy of Science and Technology
Advances in Structural Engineering | Year: 2015

This paper presents the influence of a crack on the dynamic behavior of a beam-type bridge subjected to separately or simultaneously a moving vehicle and earthquake excitation. In this study, the bridge is modelled as a 3D beam by the finite element method. The stiffness matrix of a cracked beam element with rectangular section adopted from fracture mechanics is presented. The influences of crack appearance time, crack location, crack depth, and vehicle speed on the dynamic response of the bridge are investigated. When a crack is induced during external excitation the stiffness of the structure is changed leading to a change in natural frequencies during vibration. This change in the frequency is analysed by wavelet spectrum, a time-frequency analysis which can examine locally a signal in both time and frequency domains. The relationship between the crack depth and the instantaneous frequency (IF) of the structure is established which may prove useful for assessment of the crack depth. Numerical simulation results are presented to investigate the efficiency of the method.

Dong P.V.,Vietnam Academy of Science and Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

We argue that the gauge symmetry which includes SU(3)L as a higher weak-isospin symmetry is manifestly given by SU(3)C - SU(3)L - U(1)X - U(1)N, where the last two factors determine the electric charge and B-L, respectively. This theory not only provides a consistent unification of the electroweak and B-L interactions, but also gives insights in dark matter, neutrino masses, and inflation. The dark matter belongs to a class of new particles that have wrong B-L numbers, and is stabilized due to a newly realized W-parity as residual gauge symmetry. The B-L breaking field is important to define the W-parity, seesaw scales, and the inflaton. Furthermore, the number of fermion generations and the electric charge quantization are explained naturally. We also show that the previous 3-3-1 models are only an effective theory, as the B-L charge and the unitarity argument are violated. This work substantially generalizes our recently proposed 3-3-1-1 model. © 2015 American Physical Society. © 2015 American Physical Society.

Buong N.,Vietnam Academy of Science and Technology
Computers and Mathematics with Applications | Year: 2011

In this paper, on the base of the Ishikawa iteration method and the hybrid method in mathematical programming, we give two new strong convergence methods for finding a point in the common fixed point set of a nonexpansive semigroup in Hilbert space. © 2011 Elsevier Ltd. All rights reserved.

A new species of karst-dwelling bent-toed gecko, Cyrtodactylus martini sp. nov., is described from the isolated karst formations of the Hoang Lien Son Mountain range in northwestern Vietnam. It differs from all other congeners by the presence of symmetrical or subsymmetrical reticulations on top of head; no nuchal loop; four precloacal pores separated medially by one poreless scale; 14-18 enlarged femoral scales beneath thighs continuous with precloacal scales; four to six irregular, narrow, yellowish-white bands on dorsum between limb insertions; and six or seven incomplete white rings on tail. Copyright © 2011 · Magnolia Press.

Trung N.N.,Vietnam Academy of Science and Technology
Journal of Petroleum Science and Engineering | Year: 2012

Based on the relationship among water depth, sea water temperature, geothermal gradient and geological setting, the gas hydrate potential in the South China Sea (SCS) is estimated. The thickness of the gas hydrate stability zone (GHSZ) and the minimum sea water depth in order to form the gas hydrate structures I (100% CH 4), II (95.9% CH 4) and H (90.4% CH 4) are calculated and defined by the relationship among sea water depth, seawater temperature, geothermal gradient and gas composition. The average thickness of the GHSZ in the SCS is estimated to be 225m, 270m and 365m for the gas hydrate structures I, II and H, respectively. The calculation also shows that the gas hydrate accumulation is at the water depth equal to or deeper than 600m, 400m and 300 for gas hydrate structures I, II and H, respectively. Maximum thickness area of the GHSZ in the SCS is also defined in the water depth ranging from 1200 to 2300m. By assuming that gas hydrate is distributed in one third of the calculated GHSZ area, the volume of gas hydrate reservoir is estimated to contain 1.38×10 14m 3, 1.41×10 14m 3 and 1.7 10 14m 3 of methane gas at the standard temperature and pressure (STP) for the gas hydrate structures I, II and H, respectively. © 2012 Elsevier B.V.

Nguyen D.K.,Vietnam Academy of Science and Technology
Composites Part B: Engineering | Year: 2013

The large displacement response of tapered cantilever beams made of axially functionally graded material is investigated by the finite element method. A co-rotational beam element taking the effects of the material inhomogeneity, shear deformation and nonuniform cross section into account is formulated and employed in computing the response of the beams. The numerical results show that the large displacement response of the beam is governed by the material distribution, the taper ratio and taper type. The axial displacement at the free end of the beam is most sensitive to the taper ratio, and the transverse displacement at the point is least affected by this parameter. The influence of the length to height ratio is also investigated and highlighted. © 2013 Elsevier Ltd. All rights reserved.

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