bluuebunny/crossref_metadata_2025 huggingface dataset:
Planetary cycloid roller gear reducer
Authors: Phuc Nguyen Thien
Published: April 2018

In this paper we present some results of the shaping tooth profile and the method of the relationships between gear parameters and of the analysis for properties of the planetary cycloid roller gear reducer.
Simulation of liquefied petroleum gas jet in combustion chamber of spark ignition engine
Authors: Ga Bui Van , Dung Duong Viet , Nam Tran Van
Published: April 2018

Based on the mathematical validated by experimental data, the present paper introduces the evolution of concentration and velocity fields of Liquefield Petroleum Gas (LPG) jet in combustion chamber of spark ingnition enegine under effects of injection conditions and surrounding environment. The results allow us to predict the development of jet for an efficient organization of mixture preparation and combustion process in LPG direct injection spark ignition engine
The Poincare method for a strongly nonlinear Duffing oscillator
Authors: Dinh Nguyen Van
Published: April 2018

It is well-known that the classical Poincare method is limited to weakly nonlinear systems and for extending the range of validity of this method to strongly non-linear systems, various modifications have been developed.
Calculation of the horizontal two-dimensional unsteady flows by the method of characteristics
Authors: Lich Tran Gia , Son Nguyen Minh , Cuong Le Viet
Published: April 2018

This paper will be concerned with the characteristic form of the two dimensional Saint-Venant equation system, the supplementary equations at the boundaries, the methods of characteristics for solving the equation system and some numerical experiments.
Geometric nonlinear vibration analysis of steel frames with semi-rigid connections and rigid-zones
Authors: Anh Vu Quoc , Hien Nghiem Manh
Published: April 2018

To obtain an accurate insight into the behavior of the most realistic steel frames, joint flexibility should be allowed for in the analysis. So far, most research work is concentrated on the linear and geometric nonlinear static analysis of steel frames with flexible connections. Very few papers were contributed to the dynamic and vibration analysis of these types of frames. This paper proposes a numerical method for geometric nonlinear vibration analysis of frames with semi-rigid connections and rigid-zones. The effect of initial stress due to the applied load is accounted for in the suggested method, which is believed to be more general than the existing methods and does not involve complex calculations.
Frequency entrainment in a self-oscillatory system under parametric excitation
Authors: Da Hoang Van , Sy Nguyen Thac
Published: April 2018

In the present paper, the frequencies for appearing the entrained oscillations in a self-oscillatory system under the parametric excitation, have been determined. The almost periodic oscillation which develops from the entrained oscillation when the driving frequency is given just outside the region of entrainment also have been investigated by the method of the phase plane.
A model of spreading forest fires
Authors: Quang V. D. , Nam N. T. , Lien H. D. , Antonov I. S. , Krastanska T. T.
Published: April 2018

Current article describes a mathematical model for throwing burning wood material out of a main body of fire with a help of wind. A problem is solved by numerical way and it is given some of results, which are received during numerical experiment.
TEST
Authors: Tran Trung Ngoc
Published: April 2018

Abstract
Vibration of rigid bodies in the visco-elastic Hook-Maxwell model
Authors: Dao Nguyen Van
Published: April 2018

In this paper the self-excited and forced vibrations of rigid bodies fastened to visco-elastic beam are considered. Two parameters solutions of motion equations of third order are found in the asymptotic series and their stability is investigated. It was shown that in comparison with Hook material the Hook-Maxwell material of beam limits the growth of amplitudes of both self-excited and forced vibrations. The theoretical results agree well with experimental ones.
Subharmonic oscillation in third order non-linear systems
Authors: Dao Nguyen Van
Published: April 2018

In this paper the subharmonic oscillation with frequency n times smaller than that of exciting force is considered. The first paragraph is devoted to the formulation of problem. Here an example of third order equation in which there exists pure subharmonic solution is given. In the second paragraph the condition (2.5), (2.7) for the existence of pure odd subharmonic oscillation in the dynamical system governed by equation (2.1) are derived. The mixed subharmonic oscillation is studied in the third paragraph. The family of tow parameters solutions (3.2) of equation (3.1) with subharmonic term is found by means of asymptotic method. The stationary oscillations are given by formulae (3.14)-(3.16). The stability of subharmonic is oscillation is studied by Liapunov-Routh-Hurwitz criterium in the fourth paragraph. In general, the stability conditions (4.5) lead to the results which are different from those in second order system. To illustrate the presented method a concrete example has been analysed in the fifth paragraph.
On a method for investigation of random oscillations of the linear visco-elastic system
Authors: Khiem Nguyen Tien , Anh Nguyen Dong
Published: April 2018

The paper deals with the method for investigation of the random excited integro-differential equations, appeared frequently in the theory of the visco-elastic system. By this method the linear random excited integro-differential equations can be approximated by a linear random excited differential one. In the case of non-random excited systems the results coincide with the ones obtained by averaging method' for the determined integro-differential equations.
Cách tính thanh mềm chịu uốn
Authors: Trinh Leu Tho
Published: April 2018

None
Về phương trình chuyển động của các hệ cơ học
Authors: Sanh Do
Published: April 2018

None
Tính gần đúng chuyển vị thẳng của hệ khung nhiều tầng nhiều nhịp theo thuật toán truyền nhảy nút mômen không cân bằng
Authors: Cau Vu Nhu
Published: April 2018

None
Xác định dao động của hệ có số hạng quán tính phi tuyến bằng phương pháp tham số bé
Authors: Khang Nguyen Van
Published: April 2018

None
Về tác dụng của ngẫu lực và quan hệ đối ngẫu chuyền vị - nội lực của thanh không gian
Authors: Lai Vu Dinh
Published: April 2018

None
A note on the method of harmonic balance
Authors: Dinh Nguyen Van
Published: April 2018

Free oscillation period of the Duffing oscillator with cubic non-linearity was examined. A comparison between the exact period and those obtained by the asymptotic and the harmonic balance methods was done. It was shown that the remits given by the harmonic balance are acceptable even for large oscillations whereas the asymptotic method can only be applied for small oscillations.
Calculation of the matter propagation in the river or open channel system
Authors: Lich Tran Gia
Published: April 2018

In this paper, we consider the following problems: The existence of solution the stability of finite difference scheme and the non-negative property of numerical solution
The problem of first integral of nonholonomic systems
Authors: Sanh Do
Published: April 2018

In this paper, the problem of first integrals of a nonholonomic system is discussed. The aim of this work is concentra.ted on finding the condition for existence of first integrals. The obtained results are applied for the construction of linear and quadratic integrals of nonholonomic systems. It obtains two important affirmations; they are: Any first integral could be treated as a particular nonholonomic constraint and contrarily, any nonholonomic constraint could be regarded as a first integral of the nonholonomic system.
Calculation of turbulent diffusion jets under effects of gravity and moving surrounding air
Authors: Ga Bui Van , Quang Nhan Hong , Vignon Jean Marc
Published: April 2018

The basis theory for the turbulent diffusion of jet and flame has been presented previously [1, 2]. But that one applies only in quiet surrounding air with the effects of buoyancy neglected. In the present paper, the theory is developed further by establishing an integral model for a jet in more general conditions with variable inclined angles, under effects of gravity and surrounding air velocity in any direction compared to the jet axis. The system of equations is closed by turbulence k-E model and is solved by 4th order Runge-Kutta method. In the first stage, the model is applied to predict the velocity field, the concentration field and with development of a 0.3 m diameter jet.
Taylor bubble velocity measurements in two-phase air/water vertical flow
Authors: Dinh T. Bui
Published: April 2018

An experimental technique for the measurement of the instantaneous rising velocity of a single Taylor bubble in two-phase air/water vertical flow is proposed. Measurements are based on the multiple successive digital images and binary image processing techniques. The instantaneous velocity of a bubble is expressed as a function separation distance between the two consecutive bubble nose tips (or the position of the center of the bubble). This experimental technique allows studying and measuring with high accuracy both types of flow: full developed and developing slug flows. The major part of this work(experimental set-up, images digitization) is carried out at Kwangju Institute of Science &Technology (KJIST) in Korea.
The use of vibration characteristic to update the structure model
Authors: Khang Pham Xuan
Published: April 2018

Many authors studied algorithms adjusting the structure model based on modal data. This paper proposes an algorithm to detect the structure model using correlation factors between experimental and theoretical modal data in a damage library. The result from an experiment on 1-40 bridge (New Mexico USA) is presented to illustrate.
A form of equations of motion of a mechanical system in quasi-coordinates
Authors: Sanh Do
Published: April 2018

In [3, 4, 5] the form of equations of motion in holonomic coordinates has constructed. The equations obtained give an effective tool for investigating complicated systems. In the present paper the form of equations of motion is written in quasi-coordinates. These equations are solved with respect to quasi-accelerations, which allow to define the motion of a holonomic and nonholonomic systems by a closed set of algebraic – differential equations. The reaction forces of constraints imposed on the system under consideration are calculated by means of a simple algorithm. For illustrating the effectiveness of this form of equations an example is considered.
The balancing of rotating machinery as nonlinear system
Authors: Menh Nguyen Cao
Published: April 2018

In this paper a method for dynamical balancing of rotating machines as a nonlinear system is proposed. After analyzing and identifying the nonlinear system, procedure of dynamical balance including measurement and processing of vibration signals, for calculating magnitude and location of imbalance mass is presented. An example of simulation and calculation is investigated for illustration of the method.
On Generalized q-deformed Fermionic Oscillators
Authors: Kim Thanh Luu Thi
Published: April 2018

In this work we consider a version of generalized q-deformed fermionic oscillators and some their applications. The corresponding coherent states are constructed. The statistical distribution of generalized q-deformed fermionic oscillators system, expressions for quadrature variances and the average particle number in the coherent states are calculated.
BRST Charge Operator for Generalized Deformed SU(2) Algebra
Authors: Loan Nguyen Thi Ha , Ha Nguyen Hong
Published: April 2018

The BRST Charge plays a prominent role in interaction theory based on the Gauge

symmetry group. In this work we find the explicit expression of the BRST charge for Generalized

deformed SU(2) algebra.
Quaternionic Reformulation of Generalized Superluminal Electromagnetic Fields of Dyons
Authors: Bisht Praveen Singh
Published: April 2018

Superluminal electromagnetic fields of dyons are described in T^{4}- space and Quaternion formulation of various quantum equations is derived. It is shown that on passing from subluminal to superluminal realm via quaternion the theory of dyons becomes the Tachyonic dyons. Corresponding field Equations of Tachyonic dyons are derived in consistent, compact and simpler form.
Influence of Sintering Temperature on Low-field Spin-polarized Tunneling Magnetoresistance of La0.7Ca0.3MnO3
Authors: Phong Pham Thanh , Manh Do Hung , Hong Le Van , Phuc Nguyen Xuan , Khiem Nguyen Van , Hung Vu Van
Published: April 2018

In this study we report the effect of sintering temperature on the low field magnetoresistance

(LFMR) of La0.7Ca0.3MnO3 manganite synthesized through sol-gel technique. The

La0.7Ca0.3MnO3 has been sintered at 600°C, 700°C, 800°C, 900°C and 1200°C. The crystallite

as well as particle size also show strong dependence on the sintering temperature. While

the ferromagnetic – paramagnetic (FM-PM) transition temperature remains almost constant,

the metal – insulation transition temperature drop gradual and the low field magnetoresistance

(LFMR) increase with a decrease in grain size. We have analyzed our data based on the spin –

polarized transport of conduction electrons at the grain boundaries.
Study of the Isomeric Ratio of 135m,g 54Xe in Photofission 23793Np in Giant Dipole Resonance Region
Authors: Thiep Tran Duc , An Truong Thi , Vinh Nguyen The , Cuong Phan Viet , Khai Nguyen Tuan , Gangrski Iu. P. , Penhionzkevich Iu. E. , Zemenhik V. I. , Mishinski G. V.
Published: April 2018

In this work we present the results of measurement of the isomeric ratio of fission fragment e in photofission of 237Np induced by bremsstrahlung in the Giant Dipole Resonance Region by the method using the inert gaseous flow. The experiments have been performed at the electron accelerator Microtron MT-25 of the Flerov laboratory of Nuclear Reaction, Joint Institute for Nuclear Research, Dubna, Russia. The results were discussed and compared with that of other authors.
Effect of Spontaneous Polarization Charges on the Electron Mobility in ZnO Surface Quantum Wells
Authors: Tien Nguyen Thanh , Tuan Le , Quang Doan Nhat
Published: April 2018

We present a theoretical study of the effect due to spontaneous polarization of ZnO on the low-temperature mobility of the two-dimensional electron gas (2DEG) in a ZnO surface quantum well (SFQW). We proved that for the O-polar face this causes an attraction of electrons by the positive charges bound on the surface, while for the Zn-polar face a repulsion of them far away therefrom by the negative bound charges of the same magnitude. Accordingly, surface roughness scattering is drastically enhanced in the former case, but reduced in the latter one. Therefore, the low-% temperature 2DEG mobility in ZnO SFQWs with O-polar face is found to be dominated by surface roughness. Our theory was illustrated for the sample prepared by bombardment of the O-polar face by 100-eV hydrogen ions. The surface roughness scattering enables an explanation of the 2DEG mobility, especially, the reason of low values for the mobility in the dependence from the carrier density which has not been understood when starting from impurity scattering.
Entanglement of a Scattered Single Photon and an Exciton
Authors: Giang Nguyen Duc , Van Tran Thi Thanh , Thanh Ngo Van , Viet Nguyen Ai
Published: April 2018

A single photon which is initially uncorrelated with an exciton will evolve to be entangled with the exciton on their continuous kinetic variables in the process of resonant scattering. We find the relations between the entanglement and their physical control parameters, which indicates that high entanglement can be reached by changing specific parameters of exciton.
One Loop Corrections to Decay \(\tau\rightarrow \mu\gamma\) in Economical 3-3-1 Model
Authors: Thuc Truong Trong , Hue Le Tho , Khoi Dinh Phan , Phong Nguyen Thanh
Published: April 2018

Lepton flavor violating (cLFV) decays of charged leptons such as \(\tau\rightarrow \mu\gamma\), \(\tau\rightarrow e\gamma\), \(\mu\rightarrow e\gamma\),..., are now the subjects of experiments as signals of new Physics beyond the Standard Model (SM). In the limit of the unitary gauge, we prove that contributions from one loop corrections to the above decays are very small in the framework of the economical 3-3-1 model.
Magnetism in the Interfaces of the Sandwiched PbTiO\(_3\)/LaAlO\(_3\)/SrTiO\(_3\) Hetero-structure
Authors: Giang Bach Huong , Trang Nguyen Thuy , Nam Tran Van , Cong Bach Thanh
Published: April 2018

We investigate the effect of PbTiO3 on the LaAlO\(_3\)/SrTiO\(_3\) hetero-structure by density functional theory, where the asymmetrysandwich not only forms a quasi-two dimensional electron gas but also reveals a ferromagnetic state in the TiO\(_2\) interfaces. Itis found out that magnetic moments of TiO\(_2\) interface layers are around 0.18 \(\mu_B\) while they are mostly negligible in the pure LaAlO\(_3\)/SrTiO\(_3\) system. Even though magnetic moments are mainly produced by Ti t2g orbitals, oxygen plays a key role in the formation of the ferromagnetic state since polar distortions primarily occur in oxygen positions of the SrTiO\(_3\) and PbTiO\(_3\) sides in opposite directions.
Au plasmonic effect on the Voc, Jsc and efficiency of the Au-embedded TiO2-based DSSC solar cell
Authors: Long Pham Duy
Published: April 2018

In this study the influence of the plasmonic effect of gold nanoparticles on the parameters (Voc, Jsc and efficiency) of Au-embedded TiO2-based DSSC solar cells was investigated. The gold nanoparticles were successfully embedded into the TiO2 films by means of vacuum evaporation combined with thermal annealing. A thin Au layer was deposited first on TiO2 film by the thermal evaporation then annealed at a temperature of 400 oC to get nanocomposite films. It was found that the Au nanoparticles were well dispersed on the TiO2 films and their average size changed from 14 nm to 35 nm when the deposited gold layer changed from 3 nm to 8 nm. The surface plasmon resonance (SPR) absorption spectrum of Au@TiO2 films was observed in the wavelength range from 534 nm to 614 nm, depending on the gold nanoparticles size. The Au@TiO2 thin films were used as photo-anode for manufacturing the DSSC solar cells in configuration of FTO/Au@TiO2/(I-/I2-) electrolyte/Pt. The I-V characteristics of the cells were measured under irradiation of the visible light. The results indicate that, the short-circuit current (Jsc) and open-circuit voltage (Voc) of the Au@TiO2 films based solar cell and its efficiency were much improved, due to a contribution of the surface plasmon resonance (SPR) effect
Using bioinformatic tools in exploited gene encoding enzyme to decompose lignocellulose from metagenome of free - living bacteria in the gut of the lower termite Coptotermes gestroi
Authors: Giang Nguyễn Minh , Huyền Đỗ Thị , Hải Trương Nam
Published: April 2018

Microbial metagenome DNA in the guts of Coptotermes gestroi has been extracted and sequenced by metagenomic techniques. In previous studies, we acquired and sequenced more than 5 Gb of DNA metagenome DNA of the termite gut microbiota by next-generation sequencing (Illumina). Software MGA (MetaGeneAnnotator) exploited 125.431 open reading frames with 8508 ORFs related to carbohydrate metabolism, including 587 ORFs coding for enzymes involved in the hydrolysis of lignocellulose. We identified software to reliably predict function, structure and characteristics of proteins corresponding to DNA sequences encoding alkaline enzymes from the metgenome of C gestroi. The online software Alcapred was used to predict alkaline enzymes, Blastp to predict conserved domains of amino acid sequences deduced from ORFs, Phyre2 to predict the three dimentional structure and substrate binding site of the enzymes, TBI to predict melting temperature of the enzyme. We identified 6 ORFs encoding alkaline cellulases (GL0101308, GL0038126) or alkaline hemicellulases (GL0120095, GL0074258, GL0112518, GL0067868). The amino acid sequences deduced from ORFs had 90% coverage and from 44% to 99% identity to the corresponding sequences in NCBI by BLASTP. All of them contained conserved domains with corresponding activities and binding sites of the enzyme to the substrate. The three dimentional structures of amino acid sequences were predicted by Phyre2 with reliability from 98% to 100% to the annotated activities. Among six selected amino acid sequences, two sequences of enzymes had the melting temperature above 65 ℃, three sequences had melting temperature from 55℃ to 65℃ and only one below 55℃.
Isolation and characterization of the cellulose-degrading bacteria from Ngoc Linh ginseng soil in Quang Nam province
Authors: Trâm Trần Bảo , Sơn Phạm Hương , Hiền Ngô Thị , Hoa Ngô Thị , Hiền Nguyễn Thu , Hoàng Nguyễn Huy
Published: April 2018

Ngoc Linh ginseng (Panax vietnamensis Ha et Grushv.) is an endemic species in Vietnam and was discovered at the Ngoc Linh mountain (Kon Tum/Quảng Nam). Investigations showed that the soil with a thick layer of humus was the ideal condition for growth and development of Ngoc Linh ginseng. Therefore research on microbial flora as well as cellulose-degrading bacteria in ginseng soil may elucidate factors contributing to acclimatized cultivation of this ginseng in Vietnam. From the soil sample with cultivated Ngoc Linh ginseng in Quang Nam, five bacteria strains with cellulose-degrading activities were isolated (QN1, QN2, QN3, QN4, QN5 with respectively hydrolyzed CMC halos diameters of 10, 11, 22, 7, 22 mm) with cellulase activities of 1,31; 1,23; 2,99; 0,99; 2,51 U/ml. The combination of 16S rRNA gene sequences and cultured/biochemical characteristics of the bacteria showed that the five bacteria strains was classified to be Pseudomonas sp. QN1; Pseudomonas sp. QN4; Bacillus sp. QN2; Bacillus sp. QN3; Roseomonas sp. QN5.
Effect of some factors on the growth and regeneration of cell suspension of Ngoc Linh ginseng (Panax vietnamensis Ha et Grushv.)
Authors: Cương Lê Kim , Hoàng Nguyễn Hồng , Nhựt Dương Tấn
Published: April 2018

Ngoc Linh ginseng also known as Vietnamese ginseng (Panax Vietnamensis Ha et Grushv.) is a perennial medicinal plant. This plant is extremely rare and belongs to the Araliaceae family. Scientists are focusing on studies of Ngoc Linh ginseng nowadays. In this research, the effects of 2,4-dichlorophenoxyacetic acid (2,4-D), a-naphthaleneacetic acid (NAA), indole-3-butyric acid (IBA), 6-benzylaminopurine (BA), Kinetin (KIN), mineral salt formulations and cultural conditions, pH, sucrose concentration, medium volume on cell suspension culture of Panax vietnamensis Ha et Grushv. were investigated. In addition, growth curves and the effect of several plant grow regulators including a-naphthaleneacetic acid (NAA), indole-3-butyric acid (IBA), 6-benzylaminopurine (BA) on the regeneration of Ngoc Linh ginseng‘s cell suspension were also presented in this study. After 28 days in culture, the results showed that the best growth of a cell suspension of Ngoc Linh ginseng were obtained on ½MS liquid medium supplemented with 1.5 mg/l NAA, 50 g/l sucrose and the most suitable pH was 6.3. The acceptable medium volume for cell suspension growth was 30 ml. The growth curve of Ngoc Linh ginseng’s cell suspension showed that it should be subcultured at the beginning of the stationary phase approximately the 14th-16th day of culture. Ngoc Linh ginseng’s cell suspension exhibited the strongest growth at this time. When Ngoc Linh ginseng’s cell suspension was transferred to fresh medium, somatic embryos were formed in MS medium supplemented with 3.0 mg/l NAA after 30 days culture. The results shown that the potential regeneration of cell suspension of Ngoc Linh ginseng is very high.
Isolation of stress-inducible promoter Oshox24 from rice
Authors: Hội Phạm Xuân , Nga Trần Thị Thúy , Phương Nguyễn Duy
Published: April 2018

Plant improvement based on plant transformation technology has become a popular trend all over the world. The isolation and characterization of a complete set of genes/promoters associated with abiotic stress and the cross-talk among salinity, drought or temperature stresses are required for success in generating abiotic stress-resistant varieties. Recently, several studies on model plants demonstrated that the stress-responsive genes under the control of rice promoter Oshox24 were expressed specifically under stress conditions, while not affecting plant growth under normal conditions. In this study, we isolated DNA segments carrying the Oshox24 promoter from an Indica rice variety by PCR using specific primers. The Oshox24 promoter was cloned into the pGEM-T vector and fully sequenced. The nucleotide sequence of the isolated promoter Oshox24 was 1612 bp in size and had similarity of 90% in comparison to the Japonica rice promoter Oshox24 (published in GenBank as ID AP004868.3). Results of sequence analysis showed that the Indica Oshox24 promoter contains 15 stress-responsive cis-acting elements including 5 important groups ABRE, MYBRS/MYCRS, DRE, NACRS and ZFHDRS, and a TATA box located at position 1482 to 1488, suggesting that Oshox24 promoter plays an important role on regulation of abiotic stress inducible genes. The Oshox24 promoter was inserted into the expression vector pCAMBIA1300 for generating abiotic stress resistant plants in the future.
Assessment of the mannose inhibition on tobacco regeneration for establishment of a mannose selection system for transgenic plants
Authors: Thủy Lê Thị , Hằng Triệu Thị , Nhân Lâm Đại , Sơn Lê Văn
Published: April 2018

Recently, the application of environmentally friendly methods in transgenic-plant selection has been exploited with an interest to contribute to the commercialization of transgenic products. In this study, mannose was chosen in selecting transgenic tobacco. The ability of mannose to inhibit tobacco regeneration was assessed through three stages: creating multi-shoot, elongating shoot, and rooting of tobacco cultivars K326 and C9-1. The results showed that mannose concentrations at 30 g/l and 20 g/l are suitable for creating multi-shoot of K326 and C9-1, respectively. In addition, mannose concentration at 30 g/l in combination with 7,5 g/l sucrose is fit for elongating shoot while its concentration at 30 g/l is appropriate for rooting transgenic tobacco in both K326 and C9-1 cultivars. The mannose selection of transgenic tobacco using gus gene showed that the transgenic effectiveness is ranging 16-17% of K326 and 9-11% of C9-1 cultivars. The successful establishment of mannose selection system in transgene tobacco contributes to generate bio-safety transgenic plants.
Enhancement of starch production in tobacco through transfer of the gene encoding bacterial ADP glucose pyrophosphorylase
Authors: Ngọc Lê Thu , Hưng Nguyễn Mậu , Hùng Đinh Văn , Hồng Nguyễn Thị Minh , Ngọc Phạm Bích , Hà Chu Hoàng
Published: April 2018

Starch is the primary storage polysaccharide in plants.  It not only plays a role as the most important nutritional component in the diet of humans and many animal species, but is also a raw material in the food processing industry or material industry. Therefore, a current research direction is the improvement of crops by increasing starch yields based on enhancing the activity of key enzymes involved in starch biosynthesis by genetic engineering. ADP-Glc pyrophosphorylase (AGPase) is an important regulatory enzyme for synthesis of glycogen in bacteria and starch in plants. In this paper, the 1.5 kb synthetic mutant of AGPopt gene derived from E. coli AGPase was inserted into the plant expression vector pBI121 under the control of 35S promoter. The efficiency of this construct was tested in transgenic Nicotiana tabacum. The integration of AGPopt into the plant genome was confirmed by PCR and Southern hybridization, and the expression of bacterial AGPase in transgenic lines was detected by Western hybridization. Interestingly, starch assays in 7 tobacco transgenic lines resulted in 5 lines displaying an increase in the levels of starch accumulated in the leaves, approximately 18%–56% higher than those of WT plants. These results indicate that the expression of AGPopt is one of effective strategies for enhanced starch production in plant.
Biological characterization of fungal endophytes isolated from agarwood tree Aquilaria crassna Pierre ex Lecomte
Authors: Chi Hoang Kim , Cuong Le Huu , Hang Tran Thi Nhu , Luyen Nguyen Dinh , Ha Tran Thi Hong , Huong Le Mai
Published: April 2018

In recent years, a considerable number of studies on the role of microbes in agarwood production have been carried out in plants of the species Aquilaria. Based on the fact that there is a relationship between the microorganisms residing inside the plant and the agarwood formation, we isolated and characterized endophytic fungi associated with A. crassna samples collected from Southern Vietnam. Morphological identification and DNA barcoding analysis of the fungal endophytic isolates indicated that they were classified at least into three groups of diverse genera: Geotrichum, Fusarium and Colletotrichum belonging to families Dipodascaceae, Nectriaceae and Glomerellaceae, respectively.  Noteworthy, Geotrichum candium strain SHTr1 isolated from a dark colored woody sample of agarwood was able to produce a fruity odor and exhibited a slight antimicrobial activity against the test bacterium Staphylococcus aureus. Another fungal isolate, Fusarium verticillioides SHTr3’s, showed a moderate antimicrobial activity against a test Gram positive bacteria Bacillus subtillis and S. aureus with MIC values at 50 μg.mL-1. At 200 μg.mL-1, the ethyl acetate extracts of fungal isolates F. verticillioides SHTr3 and Colletotrichum truncatum SHTrHc7 were found to have comparable scavenging abilities on DPPH-free radicals with 53.87 and 71.82%, respectively. The present results contribute to a depiction of a diverse fungal endophytic community in Vietnamese agarwood plant A. crassna and provide important information for further understanding of the role of endophytic fungi in agarwood formation and therapeutic applications of host plants in general.
Antibacterial activity of marine bacteria associated with sponges from Phu Quoc island in Vietnam
Authors: Trinh Phan Thi Hoai , Ngoc Ngo Thi Duy , Tien Phi Quyet , Hung Le Dinh , Trang Vo Thi Dieu , Hang Cao Thi Thuy , Khanh Huynh Hoang Nhu , Van Tran Thi Thanh , Ly Bui Minh
Published: April 2018

Sponge associated marine microbes recognised as potential candidate for screening and isolation of bioactive compounds. In this work, thirty-one marine bacterial strains associated with seven species of sponges collected from Phu Quoc Island, Vietnam were isolated and screened for antimicrobial activity against selected human and animal pathogens including Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Vibrio parahaemolyticus, Vibrio harveyi, Bacillus cereus, Streptococcus faecalis, Listeria monocytogenes, Proteus mirabilis and Klebsiella pneumoniae using agar well diffusion assay. Twenty-six percent of bacterial strains were found to be antibacterial producers and their activities ranged from broad spectral to species specific (P. aeruginosa, E. coli, P. mirabilis, B. cereus, and L. monocytogenes). Out of the 31 marine bacterial strains subjected to preliminary screening for antibacterial activity, 8 isolates exhibited antibacterial activity against at least two tested pathogens, that 55% against P. mirabilis, 22% against P. aeruginosa, 10% against E. coli and 6% against K. pneumoniae, B. cereus and L. monocytogenes. A strain coded 045-203-4 was found to be highly potent and was cultured for further study. The strain produced metabolites with good activity in medium contained yeast extract (0.8% w/v), glucose (0.5%) at pH 7.0 and after incubated shaking for 30 h at 150 rpm. In addition, strain 045-203-4 was analyzed for morphological and physiological characteristics. Analysis of the nucleotide sequence of 16s rRNA gene of strain 045-203-4 showed a strong similarity (99%) with that of the 16s rRNA gene of Bacillus subtilis. The present investigation reveals that the marine bacteria isolated from sponges at Phu Quoc Island can be a definite source for novel antibiotics.
Development of RB1 mutation detection method based on mRNA
Authors: Nhung Vũ Phương , Quỳnh Lê Thúy , Tôn Nguyễn Đăng , Xuân Nguyễn Thị , Hà Nguyễn Hải
Published: April 2018

Retinoblastoma (Rb) is a malignant tumor of the retina, occurring usually in children before age five. The heritable form acounting for about 40% of Rb making genetic analysis of RB1 gene is a important part of disease management. In previous study, we have successfully employed a method of direct sequencing for RB1 mutation screening from genomic DNA. However, given the large size of this gene and no reported mutation hotspots, the testing can be costly and time consuming method. To overcome this problem, we have developed a method to detect mutation from RB1 mRNA. Total RNA was isolated from blood leukocytes of a healthy individual and a Rb patient, cDNA was subsequently synthesized using reverse-transcriptase PCR. Whole cDNA of RB1 was amplified using six specific primer pairs and sequenced by Sanger method. The PCR products from healthy individual were showed as six specific bands on the agarose gel and could be used as the standard pattern of the normally spilced transcripts. Those of PCR products were sequenced successfuly and data can be aligned with the reference sequence of RB1 cDNA on the Genebanhk to identify nucleotide variants.  We also identified an upnormal splicing of RB1 gene in the Rb patient haboring a c. G1960>C mutation at the end of the exon 19 by amplification of  the RB1 cDNA fragments. Hence using RB1 mRNA test can reveal not only the silent/pathogenic mutations in the coding region of RB1, but also mutations that affect the normal spilcing of RB1 mRNA. This method reduces cost and time, can be used as the first step of RB1 analysis in Rb patients.
Construction of a stable expression system for endoglucanase in Bacillus subtilis 168M
Authors: Minh Phan Thị Tuyết , Việt Nguyễn Quốc , Thoa Nguyễn Kim , Hy Lê Gia , Mấn Trần Đình
Published: April 2018

Beta-D-1,4-endoglucanase plays an important role in biomass hydrolysis, the microorganisms in nature can synthesize this enzyme at very low activity. Together with development of biotechnology, a low enzymatic activity problem has been overcome by using the recombinant method. Several expression systems for β-D-1,4-endoglucanase were designed for use of different cell lines. In this paper, we have constructed a stable expression system for β-D-1,4-endoglucanase gene in Bacillus subtilis 168M. Three main components including the promoter (180 bp) of α–amylase gene from the host strain B. subtilis 168M, the whole open reading frame of β-D-1,4-endoglucanase (1,500 bp) gene from B. amyloliquefacient VLSH08 strain, and the terminator (81 bp) of α–amylase gene from B. licheniformis 3BT2 strain, were reconstructed via megaprimer method. Subsequently, this new reconstitution was ligated into a modified pHT43 vector which was cleaved its own promoter and signal peptide fragment (AmyQ) and transformed into the compotent B. subtilis 168M. The recombinant B. subtilis 168M carrying pHT43[Bspr.endo.Blter] vector showed β-D-1,4-endoglucanase activity at 7 U/ml, 23 times higher than that of the wild type B. amyloliquefacient VLSH08 strain. The successful design and expression of the expression system β-D-1,4-endoglucanase isolated from B. amyloliquefacient strain VLSH08 in pHT43 vector carrying the promoter of the α- amylase gene from B. subtilis strain 168M and the terminator of the α-amylase gene from B. licheniformis strain 3BT2, actively contribute effectively expression of β-D-1,4-endoglucanase for use.
Taxonomic characterization of ten Thraustochytrids strains isolated from mangrove Xuan Thuy, Nam Dinh
Authors: Hà Nguyễn Thị Hoài , Đào Phạm Thị Bích , Tuấn Nguyễn Đình
Published: April 2018

Thraustochytrids have become of considerable industrial and scientific interest in the past decade due to their health benefits. Thraustochytrids are found in a wide variety of marine habitats such as the coastal, mangrove and sediments including the deep sea. Thraustochytrids are extremely common on the detritus, macroalgae and decaying leaf, they play an important role as organic matter-degrading microorganisms Thraustochytrids are unicellular, eukaryotic, chemo-organotrophic organisms. Ten thraustochytrids strains PT269, PT270, PT273, PT274, PT279, PT284, PT285, PT287, PT81, PT84 were isolated from four locations in Xuan Thuy mangroves, Nam Dinh. In this report, classification is based on morphology and 18S rDNA sequences. Ten Thraustochytrid strains could be classified into three types of colony and four types of cell morphology. Molecular phylogenetic analysis of 18S rDNA sequences showed homology score to be 99-100% and these strains belonged to four genera in the family Thraustochytriaceae. PT269, PT279, PT284 and PT287 strains belong to Aurantiochytrium genus, they produce amoeboid cells and occur successive binary division. PT273 and PT285 strains belong to Thraustochytrium genus, thallus directly develop and cleave into sporangium. PT274 strain belong to Aplanochytrium genus with two distinct development, amoeboid cells are found, they rapidly round up and become sporangium; and successive binary cell division. PT270, PT81 and PT84 strains belong to genus Schizochytrium, they have successive binary cell division, zoospores release.
Influence of zero gravity on germination, growth, development and phenotype variation in Impatiens balsamia
Authors: Nhựt Dương Tấn , Anh Nguyễn Thị Thùy , Tuấn Nguyễn Xuân , Nam Nguyễn Bá , Luận Vũ Quốc , Huy Nguyễn Phúc
Published: April 2018

A general strategy for de novo breeding technique using zero gravity has been emerging in some countries with developed space systems including Russia, the United States of America, China and Japan. In 2011, the first Kibo-ABC programme - "Asian Seeds" - began. Seeds from plants collected in Vietnam, Indonesia, Malaysia, and Thailand including Impatiens balsamia, Antirrhinum majus, and Salvia splendens Ker-Gawl. seed collected by Tay Nguyen Institute for Scientific Research staff were transported to Kibo and then returned to the Earth after a few months. In the present study, germination, growth and development and phenotypic variation of the Impatiens balsamia “zero gravity seeds” were compared with seeds that were not transported into space. Five months after the sowing date, the results indicated that the germination rate of the zero gravity seeds were 2 times higher than the control (22.9% and 9%, respectively). There was no significant difference in some growth and development parameters including plant height, number of branches per plant, leaf diameter, stem diameter and chlorophyll content between the zero gravity seeds and the control. Interestingly, Impatiens balsamia zero gravity seeds derived plants bloomed 16 - 23 days earlier than the control. A few “zero gravity seed” seedlings, however, showed not only lower growth and development abilities than those of the control but also some phenotypic variations such as loss of apex, under-developed apex, unusually large leaf, loss of growth and development and axillary bud formation on internodes, or double petals. This result will be an important prerequisite for the study of plant breeding in space technology - a new way of breeding industry in Vietnam.
Naphthalene degradation by bacterial strain VTPG5 Isolated from oil-contaminated sediment samples collected in Baria - Vungtau
Authors: Công Lê Thị Nhi , Mai Cung Thị Ngọc , Huy Vũ Ngọc , Tuân Đỗ Văn
Published: April 2018

Naphthalene is one of the polycylclic aromatic hydrocarbons (PAHs) which cause environmental pollution leading to mutation and cancer to human. To transform and degrade naphthalene, a number of bioremediation approaches have been investigated. The fact that bacteria can utilize naphthalene as the sole source of carbon and energy was considered as high potential method to remove naphthalene. In this research, our purpose was to find highly degrading-naphthalene bacterial strains to apply in naphthalene removal from oil-polluted sites. Three bacterial strains which could well grow on naphthalene were isolated from oil contaminated sediment samples taken from coastal zones in Baria – Vungtau province. Among them, the Rhodococcus sp. VTPG5 was demonstrated to the best aromatic hydrocarbon degrader then it was selected for further investigation. The VTPG5 strain could grow with the concentration of 200 ppm and the best concentration for degrading capacity was 150 ppm. The optimal physio-chemical conditions for growth of VTPG5 were estimated at 37oC, pH 7 and concentration of NaCl 2.5% after 7 day-incubation. Using these conditions to incubation the VTPG5, by HPLC analysis it was confirmed that 99.9 % of naphthalene was degraded by VTPG5 strain with the initial concentration of 150 ppm after 7 days. The result may lead to the use of this strain in bioremediation technology to treat naphthalene and other PAH components containing in oil-polluted sediment samples.
Isolation of a methane-oxydizing bacterium for the study on single cell protein production from methane
Authors: Thu Nguyễn Thị Hiếu , Hằng Đinh Thuý
Published: April 2018

Single cell protein (SCP) can be produced from biomass of different types of microorganisms that have high protein content such as yeast, filamentous fungi, algae and bacteria. In comparison to animal and plant protein sources, this kind of protein has several advantages, namely high protein and nutrient contents, being produced in fermenters with the use of variety of organic wastes, independence in agriculture land or climate conditions. Methane oxidizing bacteria (MOB) are considered as good candidates for SCP production and have been intensively studied recently. In the present study, a MOB strain BG3 was isolated from wastewater of an anaerobic digester via enrichment and isolation procedures using methane as the only carbon and energy sources. Strain BG3 comprised of oval-shaped cells of 0,8-1´16 -1,8 μm in size, almost nonmotile. Based on comparative analyses of the 16S rDNA partial sequences, strain BG3 was identified as a member of the Methylomonas genus, the most closely related species was Methylomonas koyamae (97% homology). This was also confirmed by analyses of sequence of the pmoA gene, encoding for a-subunit in the methane-monooxygenase in the strain.  Besides methane, strain BG3 also utilized methanol for the growth. It has been shown that methane-fed culture of strain BG3 could produce 68.69 g crude protein per 100 g CDW and the according methane to biomass conversion efficiency was 2,8 m3 methane×kg-1 dry biomassas. Owing the capability of utilization of methane, the second important greenhouse gas, for the production of protein source for animal feed, strain BG3 would have a great application potential in Vietnam. Strain BG3 was designated as Methylomonas sp. BG3 and its 16S rDNA and pmoA gene sequences were deposited at the GenBank with accession numbers of KJ081955 and KJ081956, respectively.
Primary and secondary somatic embryogenesis in Jatropha curcas L. From leaf transverse thin cell layers
Authors: Loan Nguyen Thi Kim , Giap Do Dang , Tuan Tran Trong , Hien Nguyen Thi Thanh , Huy Nguyen Phuc , Du Thai Xuan , Nhut Duong Tan
Published: April 2018

An efficient method for plant regeneration in Jatropha curcas L. via primary and secondary somatic embryogenesis culture from ex vitro leaves of 6-month-old plants was presented in this study. Leaves were cut into transverse thin cell layers (tTCLs) and cultured on MS medium supplemented with kinetin (KIN) at 0.5, 1.0, 1.5, and 2.0 mg/l in combination with indole-3-butyric acid (IBA) at 0.1, 0.5, and 1.0 mg/l or 2,4-dichlorophenoxyacetic acid (2,4-D) at 1.0, 1.5 and 2.0 mg/l . The highest embryogenic callus formation rate (89.3%) was obtained on medium supplemented with 1.0 mg/l KIN and 1.5 mg/l 2,4-D. The calli were selected for the study of primary somatic embryogenesis on MS medium containing 2,4-D (0.01, 0.03, 0.05, and 0.07 mg/l) or KIN (0.5, 1.0, 1.5, and 2.0 mg/l). The highest primary somatic embryos formation rate (76.67%) was achieved on MS medium supplemented with 1.0 mg/l KIN. The primary embryos were cultured on medium supplemented with KIN (0.1, 0.5, 1.0, 1.5, and 2.0 mg/l) combined with 0.2 mg/l indole-3-butyric acid (IBA) or 0.05 mg/l 2,4-D. The combination of 1.5 mg/l KIN and 0.05 mg/l 2,4-D was suitable for secondary embryos formation. Embryos proliferated rapidly, and the highest number of secondary embryos (77.5 embryos) wasobtained from a single primary embryos inoculated. Results also showed that the addition of proline (0.75 g/l) or spermidine (0.15 mM) to the culture medium increased the number of secondary embryos considerably. The fully developed plantlets exhibiting healthy roots and shoots were obtained when somatic embryos were sub-cultured onto B5 medium containing 1.5 mg/l IBA.
Biological and taxonomical characteristics of endophytic Streptomyces TQR8-14 and its production potential of antimicrobial substance
Authors: Thao Phan Thi Hong , Linh Nguyen Vu Mai , Lien Nguyen Thi Hong , Hieu Nguyen Van
Published: April 2018

Endophytic actinomycetes colonize in living plant tissues without causing harm to the host plant. In fact, they are regarded as effective bio-control agents and plant growth promoters due to their ability to activate plant self-immunity and produce biologically active secondary metabolites. Recent studies reported higher rates in finding new strains and antimicrobial substances among endophytes than actinomycetes from soil and plant surface. In this work, endophytic actinomycetes were isolated from Ham Yen orange trees, a famous specialty of Tuyen Quang province, and screened for antimicrobial activity against plant pathogenic bacteria and fungi. The isolate TQR8-14, showing strong activity, was studied with regard to its biological and taxonomical characteristics and production of antimicrobial substance. Based on the mycelial morphology, this isolate was placed in yellow group of streptomycetes. The isolate developed milky to yellow aerial mycelia on all test media and long straight spore chains bearing smooth cylinder spores. The isolate could grow at wide range of temperature 15 to 45oC, of pH 4 to 10; on substrates such as carboxy methyl cellulose, starch, protein and chitin; and tolerated up to 3% salinity. Its 16S rDNA nucleotide sequence (1,404 bp) shared 99% similarity to Streptomyces parvus. Therefore, the isolate was named as Streptomyces parvus TQR8-14. The highest antimicrobial activity was achieved in culture on medium AH4 containing soybean meal and glucose, at 30oC and pH 7.0.