Thứ Tư, 31 tháng 5, 2017

A novel efficient two-phase algorithm for training interpolation radial basis function networks
 nterpolation radial basis function (RBF) networks have been widely used in various applications. The output layer weights are usually determined by minimizing the sum-of-squares error or by directly solving interpolation equations. When the number of interpolation nodes is large, these methods are time consuming, difficult to control the balance between the convergence rate and the generality, and difficult to reach a high accuracy. In this paper, we propose a two-phase algorithm for training interpolation RBF networks with bell-shaped basis functions. In the first phase, the width parameters of basis functions are determined by taking into account the tradeoff between the error and the convergence rate. Then, the output layer weights are determined by finding the fixed point of a given contraction transformation. The running time of this new algorithm is relatively short and the balance between the convergence rate and the generality is easily controlled by adjusting the involved parameters, while the error is made as small as desired. Also, its running time can be further enhanced thanks to the possibility to parallelize the proposed algorithm. Finally, its efficiency is illustrated by simulations. (c) 2007 Elsevier B.V. All rights reserved. Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/31018
Chemical composition of the flower essential oil of Artabotrys hexapetalus (L. f.) bhandare of Vietnam
 The pleasant smelling flower essential oil of Artabotrys hexapetalus (L. f.) Bhandare (Annonaceae) was analyzed by GC and GC/MS. Twenty-six components of the oil including sesquiterpene hydrocarbons (33.3% of the oil) and oxygenated sesquiterpenoids (47.7%) were identified. P-caryophyllene (11.4%) and caryophyllene oxide (31.5%) were identified as the major components of the oil.
Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/31011
Chemical composition of the essential oil from the rhizomes of Alpinia henryi K. Schum. of Vietnam
 The essential oil from the fresh rhizomes of Alpinia henryi K. Schum. (Zingiberaceae) collected in Vietnam was analyzed by GC and GC/MS. Twenty-five compounds, representing 86.4% of the oil, were identified. The oil was characterized by a high content of 1,8-cineole (45.1%).

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Chủ Nhật, 28 tháng 5, 2017

Arsenic in groundwater of the Red River floodplain, Vietnam: Controlling geochemical processes and reactive transport modeling
 The mobilization of arsenic (As) to the groundwater was studied in a shallow Holocene aquifer on the Red River flood plain near Hanoi, Vietnam. The groundwater chemistry was investigated in a transect of 100 piezometers. Results show an anoxic aquifer featuring organic carbon decomposition with redox zonation dominated by the reduction of Fe-oxides and methanogenesis. Enhanced PCO2 pressure causes carbonate dissolution to take place but mainly in the soil and unsaturated zone. The concentration of As increases over depth to a concentration of up to 550 mu g/L. Most As is present as As(III) but some As(V) is always found. Arsenic correlates well with NH4, relating its release to organic matter decomposition and the source of As appears to be the Fe-oxides being reduced. Part of the produced Fe(II) is apparently reprecipitated as siderite containing less As. Results from sediment extraction indicate most As to be related to the Fe-oxide fractions. The measured amount of sorbed As is low. In agreement, speciation calculations for a Fe-oxide surface suggest As(III) to constitute only 3% of the surface sites while the remainder is occupied by carbonate and silica species. The evolution in water chemistry over depth is homogeneous and a reactive transport model was constructed to quantify the geochemical processes along the vertical groundwater flow component. A redox zonation model was constructed using the partial equilibrium approach with organic carbon degradation in the sediment as the only rate controlling parameter. Apart from the upper meter a constant degradation rate of 0.15 C mmol/L/yr could explain the redox zonation throughout the aquifer. Modeling also indicates that the Fe-oxide being reduced is of a stable type like goethite or hematite. Arsenic is contained in the Fe-oxides and is first released during their dissolution. Our model further suggests that part of the released As is adsorbed on the surface of the remaining Fe-oxides and in this way may be retarded. (c) 2007 Elsevier Ltd. All rights reserved.
 Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30997
Systematic testing of an integrated systems model for coastal zone management using sensitivity and uncertainty analyses
 Systematic testing of integrated systems models is extremely important but its difficulty is widely underestimated. The inherent complexity of the integrated systems models, the philosophical debate about the model validity and validation, the uncertainty in model inputs, parameters and future context and the scarcity of field data complicate model validation. This calls for a validation framework and procedures which can identify the strengths and weaknesses of the model with the available data from observations, the literature and experts' opinions. This paper presents such a framework and the respective procedure. Three tests, namely, Parameter-Verification, Behaviour-Anomaly and Policy-Sensitivity are selected to test a Rapid assessment Model for Coastal-zone Management (RaMCo). The Morris sensitivity analysis, a simple expert elicitation technique and Monte Carlo uncertainty analysis are used to facilitate these three tests. The usefulness of the procedure is demonstrated for two examples. (C) 2006 Published by Elsevier Ltd.
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A new approach to testing an integrated water systems model using qualitative scenarios

 Integrated systems models have been developed over decades, aiming to support the decision-makers in the planning and managing of natural resources. The inherent model complexity, lack of knowledge about the linkages among model components, scarcity of field data, and uncertainty involved with internal and external factors of the real system call their practical usefulness into doubt. Validation tests designed for such models are just immature, and are argued to have some characteristics that differ from the ones used for validating other types of models. A new approach for testing integrated water systems models is proposed, and applied to test the RaMCo model. Expert knowledge is elicited in the form of qualitative scenarios and translated into quantitative projections using fuzzy set theory. Trend line comparison of the projections made by the RaMCO model and the qualitative projections based on expert knowledge revealed an insufficient number of land-use types adopted by the RaMCo model. This insufficiency makes the model inadequate to describe the consequences of the changes in socio-economic factors and policy options on the erosion from the catchment and the sediment yields at the inlet of a storage lake. (C) 2007 Elsevier Ltd. All rights reserved.
Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30973
Chemical composition of the essential oil of Ocimum Basilicum cultivated in Mongolian Desert-Gobi
 Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30964
Isolation and identification of antiplatelet aggregatory principles from the leaves of Piper lolot

The methanolic extract of Piper lolot, having shown potent inhibitory activity on platelet aggregation induced by arachidonic acid (AA) and platelet activating factor (PAF), was subjected to activity-guided isolation to yield twelve new amide alkaloids, piperlotine A-L (1-12), along with twenty-nine known compounds. Their structures were elucidated on the basis of spectroscopic analysis. The isolated compounds were tested for their inhibitory activity on the rabbit platelet aggregation. The compounds piperlotine A (1), piperlotine C (3), piperlotine D (4), piperlotine E (5), 3-phenyl-1-(2,4,6-trihydroxyphenyl)propan-1-one (21), 3-(4-methoxyphenyl)-1-(2,4,6-trihydroxyphenyl)propan-1-one (22), 1-trans-cinnamoylpyrrolidine (24), sarmentine (26), pellitorine (27), methyl 3-phenylpropionate (32), and (10S)-10-hydroxypheophorbide a methyl ester (40) showed potent antiplatelet aggregation activity.
 Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30952



An improved approximation of Bergmann's form for the Rayleigh wave velocity
 In the present paper an improved approximation for the Rayleigh wave velocity in isotropic elastic solids is obtained using the method of least squares. It is of Bergmann's form, i.e. the form of the ratio of two binomials. It is shown that this approximation is the best one of the Rayleigh wave velocity, in the sense of least squares, with respect to the class of functions whose elements are the ratio of two binomials. This approximation is much more accurate than Bergmann's one. Its maximum percentage error is 10 times smaller than that of Bergmann's. It is 7.6 times better than the one obtained recently by Royer and Clorennec [ D. Royer, D. Clorennec, An improved approximation for the Rayleigh wave equation, Ultrasonics 46 (2007) 23-24]. An approximation of Bergmann's form for the squared Rayleigh wave velocity is also derived and its maximum percentage error is 5 times smaller than that of Royer and Clorennec's approximation. Some polynomial approximations with very high accuracy are also obtained. (c) 2007 Elsevier B.V. All rights reserved.

Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30941
The contribution of the exchange biased field direction in multilayer thin films to planar Hall resistance
Recently, planar Hall effect (PHE) has been widely pursued due to its application potential for biosensors. Planar Hall sensor is based on the anisotropy magnetoresistance and exhibits many advantages, such as large signal-to-noise ratio at low frequencies and high sensitivity at low applied field. The planar Hall resistance (PHR) curve in multilayer thin films with spinvalve structure has pre-eminent sensitivity when compared to single layer and bilayer thin films. In this work, we report a model for PHR calculation that includes the behaviour of single domain basic structure in the external magnetic field. Our results show a qualitative dependence between PHR curves and the angle (beta) between the exchange biased field direction and the easy axis of the free layer. As the beta increases the sensitivity of the PHR curves also increases. Further, it is shown that our calculation helps to determine the exchange biased field direction. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Influence of Nb substituted for Fe on the microstructure and magnetic properties of Fe-based nanocomposite alloy

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Thứ Bảy, 27 tháng 5, 2017

Planar Hall resistance sensor for biochip application

 in this work, we introduce a new type of sensor by using planar Hall effect in spin valve structure for biochip application due to advantage of increasing sensor sensitivity. A single Dynabeads (R) M-280 Streptavidin detection has been accomplished with the sensor pattern size of 3 X 3 mu m(2) that was fabricated from NiFe(6.0 nm)/Cu(3.5 nm)/NiFe(3.0 nm)/IrMn(10.0 nm) spin valve structure. Furthermore, it is also developed to integrated arrays by including 24 sensor patterns. In comparison with the other groups, our sensor performance is highlighted with the advantages of increased stability and high signal to noise; as such, the planar Hall effect sensor's behavior has proved a possibility for detection of the biomolecule. It is also feasible to provide a vehicle for studying other molecule interactions, particular single DNA molecule and for the detection of binding of the streptavidin functionalized magnetic beads to sensor bound biotin. Due to the simple fabrication scheme, this kind of Planar Hall effect based sensor can be easily integrated into other systems for applications. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30911
Cytochrome P3A4 inhibitors and other constituents of Fibraurea tinctoria

 Four ne v furanoditerpenoids, fibrauretin A (1), fibrauretinoside A (2), epi-fibrauretinoside A (3), and epi-12-palmatoside G (4), and a new ecdysteroid glucoside, fibraurecdyside A (5), together with seven known compounds including two furanoditerpenoids (6 and 7), an ecdysteroid (8), and four quaternary protoberberine alkaloids (9-12) were isolated from the stems of Fibraurea tinctoria. The structures of 1-5 were established on the basis of spectroscopic evidence. Among these compounds, palmatine (9) and jatrorrhizine (10) showed inhibitory effects against cytochrome P450 3A4 (CYP3A4) with IC50 values of 0.9 and 2.1 mu M, respectively.

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Crotonkinins A and B and related diterpenoids from Croton tonkinensis as anti-inflammatory and antitumor agents

 Cytotoxicity-guided phytochemical investigation of a methanolic extract of Croton tonkinensis afforded two new kaurane diterpenoids (1, 2) and 10 known ent-kaurane-type diterpenoids (3-12). The structures of I and 2 were based on analysis of spectroscopic and mass spectral data. Compounds 3-12 were identified by comparison of their spectroscopic and physical data with those reported in the literature. Selected compounds from this plant were examined for cytotoxic and anti-inflammatory activities. Compounds 4 and 9 showed the highest cytotoxic activity against the tested tumor cell lines. Compounds 3, 4, 6, 8, 9, and 11 had IC50 values less than 5 mu M and were more potent than the nonspecific NOS inhibitor L-NAME in inhibiting LPS-induced NO production.
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Strict partitions and discrete dynamical systems

 We prove that the set of partitions with distinct parts of a given positive integer under dominance ordering can be considered as a configuration space of a discrete dynamical model with two transition rules and with the initial configuration being the singleton partition. This allows us to characterize its lattice structure, fixed point, and longest chains as well as their length, using Chip Firing Game theory. Finally, we study the recursive structure of infinite extension of the lattice of strict partitions. (c) 2007 Elsevier B.V. All rights reserved

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Optical transitions in polarized CdSe, CdSe/ZnSe, and CdSe/CdS/ZnS quantum dots dispersed in various polar solvents

 The optical transitions in ensembles of colloidal CdSe-based quantum dots (QDs) have been systematically studied as a function of the net QDs' polarity/polarization and of the solvent's polarity. While the general trend observed for all QD systems dispersed in different solvents is similar, the spectral shifts are more pronounced in core QDs than in core/shell structures. Our results can be rationalized by taking account of the electric field experienced by the QDs that results from their effective polarization in solvents of different polarities (quantum confined Stark effect) as well as from the effect of the external dielectric environment (solvatochromatic effect). (C) 2007 American Institute of Physics.

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Thứ Năm, 25 tháng 5, 2017

Tin-dioxide nanocrystals as Er3+ luminescence sensitizers: Formation of glass-ceramic thin films and their characterization

 Silica-tin dioxide thin films doped with Er3+ ions were fabricated and investigated. Different parameters such as heat-treatment temperatures, molar concentrations of SnO2 as well as Er3+ ions concentration were changed in order to obtain the best properties of presented thin films. Using several techniques, thin films were characterized and proved to be crack-free, water-free and smooth after a heat-treatment at 1200 degrees C Aiming to application in optics, the transparency of thin films was also evidenced by transmission spectra. Based on the photoluminescence measurements, the mechanism of energy transfer from SnO2 nanocrystals to Er3+ ions was examined and discussed. (C) 2016 Elsevier B.V. All rights reserved.
Mời bạn đọc xem tại đây http://repository.vnu.edu.vn/handle/VNU_123/28880
Constituents of the Rhizomes of Boesenbergia pandurata and Their Antiausterity Activities against the PANC-1 Human Pancreatic Cancer Line

 Human pancreatic cancer cell lines have a remarkable tolerance to nutrition starvation, which enables them to survive under a tumor microenvironment. The search for agents that preferentially inhibit the survival of cancer tells under low nutrient conditions represents a novel antiausterity strategy in anticancer drug discovery. In this investigation, a methanol extract of the rhizomes of Boesenbergia pandurata showed potent preferential cytotoxicity against PANC-1 human pancreatic cancer cells under nutrient-deprived conditions, with a PC50 value of 6.6 mu g/mL. Phytochemical investigation of this, extract led to the isolation of 15 compounds, including eight new cyclohexene chalcones (1-8). The structures of the new compounds were elucidated by NMR spectroscopic data analysis. Among the isolated compounds obtained, isopanduratin A1 (14) and nicolaioidesin C (15) exhibited potent preferential cytotoxicity against PANC-1 human pancreatic canter cells under nutrition deprived conditions, with PC50 values of 1.0 and 0.84 mu M, respectively.

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DNA barcoding of East Asian Amentotaxus (Taxaceae): Potential new species and implications for conservation

DNAbarcoding is a useful tool for species identification using standardized genomic DNA fragments. The genusAmentotaxus, consisting offive or six species, is confined to South China, Northeast India, Laos, and Vietnam. All species have been assessed as globally or nationally threatened. However, there is uncertainty about the number of species involved, especially in the border areas of southern China, northern Vietnam, and Laos. We selectedfive DNA barcodes (rbcL,matK,trnH-psbA,trnL-F, and internal transcribed spacer (ITS)) to evaluate their discrimination ability in this genus, and to investigate the current taxonomy ofAmentotaxus. Our results indicate that all the selected barcoding regions showed a high level of universality for PCR and sequencing. When six species are recognized, thenuclear ribosomal DNA region ITS and the chloroplast DNA regiontrnL-Fusedon their ownprovided the highest identification success (60%). Two barcode combinations that included either ITS ortrnL-Fhad the same species discrimination ability. Combinations using additional barcodes did not improve the species identification success. When only five species are recognized, withA. hatuyenensisT. H. Nguyen treated as a synonym of A. yunnanensisH. L. Li, the discrimination rate rises to 100%. Our results also indicate that recent collections from Yunnan province, China, Lao Cai province, Vietnam, and Laos may represent a potential new species. Thefindings from this study will be very useful for the formulation of appropriate conservation strategies for threatened Amentotaxusspecies in national and trans-boundary regions.
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Polygonum multiflorum root extract as a potential candidate for treatment of early graying hair

 Despite Polygonum multiflorum (PM) has been experiencely used as a drug to treat early graying hair phenomenon in Asian countries for a long time, there is limited study examined the real biological effects of PM on hair graying in vitro and in vivo. In this study, we investigated the effects of PM root extract (PM-RE) on melanin synthesis in human melanoma SKMEL-28 cells and embryos/larvae of wild-type strain AB zebrafish. We also preliminary revealed the molecular mechanism of early hair graying phenomenon in both in vitro and in vivo models. Our results showed that PM-RE significantly induced melanin synthesis in melanin-producing SKMEL-28 melanoma cells and also in zebrafish embryos/larvae at 4-day postfertilization through activation of MC1R/MITF/tyrosinase-signaling pathway. We also investigated the differences in genotype between graying hair follicle and black hair follicle of young peoples and found that early hair graying phenomenon may be related to downregulation of MC1R/MITF/tyrosinase pathway. Taken together, we suggested that PM-RE at safe doses could be used as a potential agent for the treatment of early hair graying and other loss pigmentation-related diseases.
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Contamination of drinking water resources in the Mekong delta floodplains: Arsenic and other trace metals pose serious health risks to population

 This study presents a transnational groundwater survey of the 62,000 km 2 Mekong delta floodplain (Southern Vietnam and bordering Cambodia) and assesses human health risks associated with elevated concentrations of dissolved toxic elements. The lower Mekong delta generally features saline groundwater. However, where groundwater salinity isb1gL −1 Total Dissolved Solids (TDS), the rural population started exploiting shallow groundwater as drinking water in replacement of microbially contaminated surface water. In groundwater used as drinking water, arsenic concentrations ranged from 0.1–1340 µg L −1 , with 37% of the studied wells exceeding the WHO guidelines of 10 µg L −1 arsenic. In addition, 50% exceeded the manganese WHO guideline of 0.4 mg L −1 , with concentrations being particularly high in Vietnam (range 1.0–34 mg L −1 ). Other elements of (minor) concern are Ba, Cd, Ni, Se, Pb and U. Our measurements imply that groundwater contamination is of geogenic origin and caused by natural anoxic conditions in the aquifers. Chronic arsenic poisoning is the most serious health risk for the ~2million people drinking this groundwater without treatment, followed by malfunction in children's development through excessive manganese uptake. Government agencies, water specialists and scientists must get aware of the serious situation. Mitigation measures are urgently needed toprotect the unaware people from such health problems. Published by Elsevier Ltd.

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Persistent organic pollutants in Vietnam: Environmental contamination and human exposure

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Extragradient algorithms extended to equilibrium problems

 We make use of the auxiliary problem principle to develop iterative algorithms for solving equilibrium problems. The first one is an extension of the extragradient algorithm to equilibrium problems. In this algorithm the equilibrium bifunction is not required to satisfy any monotonicity property, but it must satisfy a certain Lipschitz-type condition. To avoid this requirement we propose linesearch procedures commonly used in variational inequalities to obtain projection-type algorithms for solving equilibrium problems. Applications to mixed variational inequalities are discussed. A special class of equilibrium problems is investigated and some preliminary computational results are reported.

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NAD-Malic Enzyme Affects Nitrogen Fixing Activity of Bradyrhizobium japonicum USDA 110 Bacteroids in Soybean Nodules

 The NAD(+)-dependent malic enzyme (DME) has been reported to play a key role Supporting nitrogenase activity in bacteroids of Sinorhizobium meliloti. Genetic evidence for a similar role in Bradyrhizobium japonicum USDA110 was obtained by constructing a dine mutant. Soybean plants inoculated with a dme mutant did not show delayed nodulation, but formed small root nodules and exhibited significant nitrogen-deficiency symptoms. Nodule numbers and the acetylene reducting activity per nodule as a dry weight value 14 and 28 days after inoculation with the dme mutant were comparable to those of plants inoculated with wild-type B. japonicum. However, shoot dry weight and acetylene reducting activity per nodule decreased to ca. 30% of the values in plants with wild-type B. japonicum. The sucrose and organic acid (malate, succinate, acetate, alpha-ketoglutarate and lactate) contents of the nodules were investigated. Amounts of sucrose, malate and alpha-ketoglutarate increased on inoculation with the dine mutant, suggesting that the decreased DME and nitrogenase activities in the bacteroids resulted in a reduction in the consumption of these respiratory metabolites by the nodules. The data suggest that the DME activity of B. japonicum bacteroids plays a role in nodule metabolism and supports nitrogen fixation.

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New 3-level response surface designs constructed from incomplete block designs

Box and Behnken [1958. Some new three level second-order designs for surface fitting. Statistical Technical Research Group Technical Report No. 26. Princeton University, Princeton, NJ; 1960. Some new three level designs for the study of quantitative variables. Technometrics 2, 455-475.] introduced a class of 3-level second-order designs for fitting the second-order response surface model. These 17 Box-Behnken designs (BB designs) are available for 3-12 and 16 factors. Although BB designs were developed nearly 50 years ago, they and the central-composite designs of Box and Wilson [1951. On the experimental attainment of optimum conditions. J. Royal Statist. Soc., Ser. B 13, 1-45.] are still the most often recommended response surface designs. Of the 17 aforementioned BB designs, 10 were constructed from balanced incomplete block designs (BIBDs) and seven were constructed from partially BIBDs (PBIBDs). In this paper we show that these seven BB designs constructed from PBIBDs can be improved in terms of rotatability as well as average prediction variance, D- and G-efficiency. In addition, we also report new orthogonally blocked solutions for 5, 8, 9, 11 and 13 factors. Note that an 11-factor BB design is available but cannot be orthogonally blocked. All new designs can be found at http://www.math.montana.edu/-jobo/bbd/. (C) 2007 Elsevier B.V. All rights reserved.

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Chemical constituents from Abutilon indicum

 The investigation on the chemical constituents of the whole plant of Abutilon indicum has resulted in the isolation of two new compounds, abutilin A (1) and (R)-N-(1 '-methoxycarbonyl- 2 '-phenylethyl)-4-hydroxybenzamide (2), as well as 28 known compounds. The structures of the two new compounds were established on the basis of the spectroscopic analysis, and the known compounds were identified by comparison of their spectroscopic and physical data with those reported in the literature.

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The higher Tamm-Dancoff approximation: Theoretical context and phenomenological aspects

 We present the key aspects of the theoretical foundations of the Higher Tamm-Dancoff Approximation which can be interpreted as a truncated shell-model approach based on a Hartree Fock solution, ensuring the conservation of the particle number. Then we discuss some phenomenological aspects of the residual interactions used, namely the delta interaction to describe the neutron neutron and proton proton pairing correlations and the quadrupole-quadrupole interaction to describe vibrational correlations.

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Criticizing in an L2: Pragmatic strategies used by Vietnamese EFL learners

 Criticizing has been a rather under-represented speech act in interlanguage pragmatics (ILP) literature. Native speakers (NSs) find this speech act challenging, often needing to pre-plan how to perform it (Murphy & Neu 1996). Thus, it can be expected that second-language (L2) learners will also experience considerable difficulty. This paper reports a study of the pragmatic strategies used by Vietnamese learners of English as a foreign language (EFL) when criticizing in English with a view to shedding light on the pragmatic properties of this under-researched act. Interlanguage data were collected from 36 adult learners via a peer-feedback task, a written questionnaire, and a retrospective interview. First and second language baseline data were collected from two respective groups of 12 Vietnamese NSs and 12 NSs of Australian English, via the same peer feedback task and questionnaire. Results showed that the English language learners criticized in significantly different ways from the Australian NSs in terms of their preference for realization strategies, their choice of semantic formulae, and their choice and frequency of use of mitigating devices. A number of interplaying factors might explain these differences: learners' limited L2 linguistic competence and lack of fluency, which seemed to load their processing capability under communicative pressure, their lack of L2 pragmatic knowledge, and the influence of L1 pragmatics.

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Streamlining the Design of MEMS Devices: An Acceleration Sensor
 A synthesis and optimization process is proposed and applied to the design of a specific MEMS device, namely an acceleration sensor. The design synthesis methodology exploits the fast and accurate simulation of the SUGAR tool (based on modified modal analysis) along with the full simulation capability of ANSYS (based on the finite element method). A three degrees-of-freedom piezoresistive acceleration sensor was designed to validate the proposed design flow. During the course of design, the modified nodal analysis and the finite element methods were combined in optimizing the sensor structure. In the latter, the piezoresistance effect was employed in sensing the acceleration in three dimensions.
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Holding the line: family responses to pregnancy and the desire for a child in the context of HIV in Vietnam

 Health services around the world offer many guidelines for HIV-positive women who are pregnant or who want to become pregnant, and for women with HIV infected partners. These guidelines are addressed to women and, increasingly, also to men, but pay little or no attention to the role of other members of the family in fertility decisions. This study looked at factors influencing decisions about fertility in families with an HIV-positive member. In Vietnam, the whole family takes a crucial role in deciding whether a woman should become pregnant and whether she will keep her child. This decision is taken in the context not only of the close family but also under the influence of ancestors and the weight given to them within the culture. Key in this regard is the need for parents and grandparents to have male offspring. Health workers share these ideas about preferred family composition and support men and women in the quest for male offspring. Policies and guidelines should take into account these additional family factors and goals as a basis for the design of appropriate programmes to reduce HIV transmission.

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Dealing with a positive result: routine HIV testing of pregnant women in Vietnam

 HIV testing is an essential component of PMTCT. It can be offered to pregnant women through different testing models, ranging from voluntary counseling and testing (VCT) to routine and mandatory testing. This study was conducted in Hanoi, Vietnam, where HIV-prevalence is low among the general population, but high among young, urban, sexually active, male intravenous drug users. Women who want to deliver in a state hospital are routinely tested for HIV in the absence of well-defined opt-out procedures. In-depth interviews with a convenience sample of 38 seropositive pregnant women and mothers and 53 health workers explored the acceptability of routine testing. Patients and healthcare workers appeared to accept routine 'blood' tests (including HIV tests) because they feel uncomfortable discussing issues specific to HIV/AIDS. To avoid having to inform women directly about their HIV status, health workers at routine testing sites rely on the official notification system, shifting the responsibility from the hospitals to district and commune health staff. The notification system in Hanoi informs these local officials about the HIV status of people living in their catchment area without patients' consent. Our study shows that this non-confidential process can have serious social, economic and health consequences for the HIV-positive women and their children.

 Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30385
Magnetic sensors based on piezoelectric-magnetostrictive composites

 Magnetoelectric (ME) composites have been fabricated by sandwiching a lead titanate (PZT) laminate between two magnetostrictive (Tb(Fe0.55Co0.45)1.5) (known as Terfecohan) films. Giant ME effect at low fields obtained is associated to large magnetostriction as well as high magnetostrictive susceptibility of the Terfecohan films. Magnetoelectric voltage coefficients,αE=(∂E/∂H), as large as 3350 and 9650 V m/kA m were achieved, respectively, for the as-deposited, and annealed films. The coefficientαEwas, however, highly dependent on the direction of the magnetic field with respect to the electrical polarization. On the basic of this magnetoelectric composite, a magnetic sensor operating in an ac magnetic field of 0.1 mT at a resonant frequency of 40 Hz has been prepared. The ME voltage response in applied magnetic fields (dVME/dH)as large as 130 mV/mT was obtained.

 Mời bạn đọc xem tại đây:  http://repository.vnu.edu.vn/handle/VNU_123/30377
Economic reforms and mangrove forests in central Vietnam

 Community-based natural resource management (CBNRM) is increasingly viewed as especially suitable for promoting the sustainable development of common-pool resources. It is considered an alternative to state control or privatization because it ostensibly brings about decentralization, meaningful participation, and conservation. Although attracting international attention, CBNRM has not been widely implemented in Vietnam, where the main strategies are centralized management by state agencies and assignment of management responsibility to individual households. Findings are presented of a study of mangrove forest use and management in a commune in central Vietnam since the introduction of economic reforms in 1986. This article argues that the promotion of nationalization or privatization, rather than solving problems of resource degradation and overexploitation, has deprived many rural households of their livelihoods. Further research is needed to define what mix of economic incentives and state and community regulation will best achieve and maintain sustainable and equitable management of local resources.
Mời bạn đọc xem tại đây:  http://repository.vnu.edu.vn/handle/VNU_123/30371
Improved parallel-iterated pseudo two-step RK methods for nonstiff IVPs

 The aim of this paper is to consider a parallel predictor–corrector (PC) iteration scheme for a general class of pseudo two-step Runge–Kutta methods (PTRK methods) of arbitrary high-order for solving first-order nonstiff initial-value problems (IVPs) on parallel computers. Starting with ans-stage pseudo two-step RK method of orderp ∗ withwimplicit stages, we apply a highly parallel PC iteration process inPE(CE) m Emode. The resulting parallel PC method can be viewed as a parallel-iterated pseudo two-step Runge–Kutta method (PIPTRK method) with an improved (new) predictor formula and therefore will be called the improved PIPTRK method (IPIPTRK method). The IPIPTRK method uses an optimal number of processors equal tow p ∗ /2. Numerical experiments show that the IPIPTRK methods proposed in this paper are superior to the efficient sequentialDOPRI5andDOP853 codes and parallel PIRK methods available in the literature.

Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30363
Spectra profile expansion of Bragg wavelength on nano-particle embedded fiber-Bragg-grating

 This article presents the results of a detailed study on the effects of spectra profile expansion of Bragg wavelength on the performance of the nano-particle embedded fiber-Bragg-grating (nano-EFBG) for sensing applications. The fiber-Bragg- grating (FBG) was coated by CdSe-nano-particle layers with various thicknesses (600-2000 nm) and bonded on substrates of epoxy or epoxy/Teflon with a large thermal expansion coefficient. With this embedding method, a variation of the line-width expansion of Bragg wavelength with cooling down FBG has been controlled. The nano-EFBG morphology was investigated by FE-SEM and the nano-EFBG sensors are studied in ambient from 77 K (liquid nitrogen) to 393 K. The expansion of spectral profile, which caused by transverse loading from nano-particle/epoxy layers, can be changed in the range of 0.1-1.3 nm between before and after cooling down. This result is for the strain-temperature sensors, but has the potential application in the FBG dispersion compensation devices and many other measurands.

 Mời bạn đọc xem tại đây:   http://repository.vnu.edu.vn/handle/VNU_123/30359
Coastal livelihood transitions: Socio-economic consequences of changing mangrove forest management and land allocation in a commune of Central Vietnam



Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30353http:
Adaptation of turbo coding and equalization in turbo equalization for time-varying and frequency-selective channels

Mời bạn đọc tra cứu tại đây:   http://repository.vnu.edu.vn/handle/VNU_123/30347






Thứ Tư, 24 tháng 5, 2017

Giáo trình lý thuyết tài chính - tiền tệ

Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/34243
Hydrological and sedimentary controls leading to arsenic contamination of groundwater in the Hanoi area, Vietnam: The impact of iron-arsenic ratios, peat, river bank deposits, and excessive groundwater abstraction

 Groundwater contamination by arsenic in Vietnam poses a serious health threat to millions of people. In the larger Hanoi area, elevated arsenic levels are present in both, the Holocene and Pleistocene aquifers. Family-based tubewells predominantly tap the Holocene aquifer, while the Hanoi water works extract more than 600,000 m(3)/day of groundwater from the Pleistocene aquifer. Detailed groundwater and sediment investigations were conducted at three locations exhibiting distinct geochemical conditions, i.e., i) high levels of dissolved arsenic (av. 121 mu g/L) at the river bank, ii) low levels of dissolved arsenic (av. 21 mu g/L) at the river bank and, iii) medium levels of dissolved arsenic (60 mu g/L) in an area of buried peat and excessive groundwater abstraction. Seasonal fluctuations in water chemistry were studied over a time span of 14 months. Sediment-bound arsenic (1.3-22 mu g/g) is in a natural range. Arsenic correlates with iron (r(2) > 0.8) with variation related to grain size. Sediment leaching experiments showed that arsenic can readily be mobilized at each of the three locations. Low levels of arsenic in groundwater (<10 mu g/L) generally exhibit manganese reducing conditions, whereas elevated levels are caused by reductive dissolution under iron- and sulphate reducing conditions. Average arsenic concentrations in groundwater are twofold higher at the river bank than in the peat area. The lower levels of arsenic contamination in the peat area are likely controlled by the high abundance of iron present in both the aqueous and sediment phases. With median molar Fe/As ratios of 350 in water and 8700 in the sediments of the peat area, reduced iron possibly forms new mineral phases that resorb (or sequester) previously released arsenic to the sediment. Despite similar redox conditions, resorption is much less significant at the river bank (Fe/As(aq)=68, Fe/As(s)=4700), and hence, arsenic concentrations in groundwater reach considerably higher levels. Drawdown of Holocene water to the Pleistocene aquifer in the peat area, caused by the pumping for the Hanoi water works, clearly prornotes reducing conditions in Pleistocene groundwater. This demonstrates that excessive abstraction of water from deep wells, i.e.. wells tapping water below the arsenic burdened depth, can cause a downward shift of iron-reducing conditions and concurrently mobilize arsenic along the way. Vertical migration of reduced groundwater may also impact aquifers under natural hydrological conditions. Seepage of DOC-enriched groundwater derived from degradation of organic matter in the clayey sediments at the river bank was observed to enhance (and maintain) iron-reducing conditions in the aquifer where organic matter is scarce. Once the aquifer becomes reduced, arsenic is released from the aquifer solid-hosts but additionally derives from the arsenic-enriched groundwater seeping from the clay into the aquifer. This behaviour is an important mechanism for arsenic contamination in aquifers that might not necessarily contain enough organic matter in their sediments to induce reducing conditions independently.

Mời bạn đọc xem tại đây:  http://repository.vnu.edu.vn/handle/VNU_123/30340
Divalent manganese in A-position of perovskite cell: X-ray absorption finite structure study of La(0.6)Sr(0.4-x)MnTi(x)O(3) manganites

Local structure and magnetic properties of Ti doped A-site deficient La(0.6)Sr(0.4-x)MnTi(x)O(3+delta) manganites (0.15 >= x >= 0) have been studied. The compositions belong to rhombohedral R (3) over barc phase. Segregation of (La(0.6)Sr(0.4-x)Mn(y))(Mn(1-y-z)Ti(x))O(3+delta) phase and fallout of (z/3)Mn(3)O(4) oxide was observed with x increase. Some amount (y) of Mn, being in divalent valence state, occupies the A (=La,Sr)-position of perovskite cell. Samples with x=0 and 0.05 are ferromagnetic with Curie temperature T(C)=350 and 172 K, respectively. Samples with x=0.1 and 0.15 are in spin(cluster)-glass states at low temperatures. (c) 2008 American Institute of Physics.
Mời bạn đọc tra cứu tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30331
Ownership, organization, and income inequality: Market transition in rural Vietnam


 In transitional economies, the scale of economic enterprise and the allocation of property rights shape social structures and influence income distribution. In agrarian economies, where labor-intensive family enterprises dominate, political officials' income advantages decline rapidly relative to those of private entrepreneurs. Larger enterprises, however provide greater income opportunities for officials, especially when a government retains an ownership stake in the initial phases of reform. This article replicates the findings from an earlier study of rural China using comparable survey data from Vietnam. We find that during the first two decades of rural market reform in Vietnam and China, the scale and ownership of firms differed radically. Small family enterprises dominated rural development in Vietnam, whereas China development was dominated by larger firms, initially established by rural governments. Consequently, while cadre income advantages have kept pace with those of private entrepreneurs in China, they have declined rapidly in Vietnam.

Mời bạn đọc tham khảo tại đây:  http://repository.vnu.edu.vn/handle/VNU_123/30319
Characteristics of polyimide-based composite membranes fabricated by low-temperature plasma polymerization





http://repository.vnu.edu.vn/handle/VNU_123/30303
Ab initio study of the optical phonons in one-dimensional antiferromagnet Ca(2)CuO(3)

http://repository.vnu.edu.vn/handle/VNU_123/30276
Acceleration of fast multipole method using special-purpose computer GRAPE

http://repository.vnu.edu.vn/handle/VNU_123/30269
Effects of dilution on magnetic and transport properties of La(0.7)Ca(0.3)Mn(1-x)M(x)(')O(3)

http://repository.vnu.edu.vn/handle/VNU_123/30256
Occurrence, fate and antibiotic resistance of fluoroquinolone antibacterials in hospital wastewaters in Hanoi, Vietnam

 Occurrence and behavior of fluoroquinolone antibacterial agents (FQs) were investigated in hospital wastewaters in Hanoi, Vietnam. Hospital wastewater in Hanoi is usually not treated and this untreated wastewater is directly discharged into one of the wastewater channels of the city and eventually reaches the ambient aquatic environment. The concentrations of the FQs, ciprofloxacin (CIP) and norfloxacin (NOR) in six hospital wastewaters ranged from 1.1 to 44 and from 0.9 to 17 mu g l(-1), respectively. Total FQ loads to the city sewage system varied from 0.3 to 14 g d(-1). Additionally, the mass flows of CIP and NOR were investigated in the aqueous compartment in a small wastewater treatment facility of one hospital. The results showed that the FQ removal from the wastewater stream was between 80 and 85%, probably due to sorption on sewage sludge. Simultaneously, the numbers of Escherichia coli (E. coli) were measured and their resistance against CIP and NOR was evaluated by determining the minimum inhibitory concentration. Biological treatment lead to a 100-fold reduction in the number of E. coli but still more than a thousand E. coli colonies per 100 ml of wastewater effluent reached the receiving water. The highest resistance was found in E. coli strains of raw wastewater and the lowest in isolates of treated wastewater effluent. Thus, wastewater treatment is an efficient barrier to decrease the residual FQ levels and the number of resistant bacteria entering ambient waters. Due to the lack of municipal wastewater treatment plants, the onsite treatment of hospital wastewater before discharging into municipal sewers should be considered as a viable option and consequently implemented

Mời bạn đọc tham khảo tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30251
Stability radii of differential algebraic equations with structured perturbations

 This paper deals with a formula for computing stability radii of a differential algebraic equation of the form A X 0 (t ) − B X (t ) = 0, where A, B are constant matrices. A computable formula for the complex stability radius is given and a key difference between the ordinary differential equation (ODEs for short) and the differential algebraic equation (DAEs for short) is pointed out. A special case where the real stability radius and the complex one are equal is considered.

Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30242
Improved approximations of the Rayleigh wave velocity

 Mời bạn đọc tra cứu tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30237
Persistent organochlorine residues in estuarine and marine sediments from Ha Long Bay, Hai Phong Bay, and Ba Lat Estuary, Vietnam

 Mời bạn đọc tra cứu tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30129
Polymeric thermal microactuator with embedded silicon skeleton: Part II - Fabrication, characterization, and application for 2-DOF microgripper

http://repository.vnu.edu.vn/handle/VNU_123/30127
Concentrations of atmospheric polycyclic aromatic hydrocarbons in particulate matter and the gaseous phase at roadside sites in Hanoi, Vietnam

 Mời bạn đọc nghé thăm tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30125
An algorithmic approach to constructing mixed-level orthogonal and near-orthogonal arrays

 Mời bạn đọc xem tay đây: http://repository.vnu.edu.vn/handle/VNU_123/30119
Salinization problems in the NEGB: results from thermohaline simulations
 Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30117
Salinization of groundwater in the North German Basin: results from conjoint investigation of major, trace element and multi-isotope distribution

 Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30114
A generalization of Ostrowski inequality on time scales for k points

 Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30112
Analysis Method of Microstrip Antennas on Hemispherical Multilayer Structures

http://repository.vnu.edu.vn/handle/VNU_123/30109
Semi-supervised learning integrated with classifier combination for word sense disambiguation

http://repository.vnu.edu.vn/handle/VNU_123/30108
On data-dependence of exponential stability and stability radii for linear time-varying differential-algebraic systems

http://repository.vnu.edu.vn/handle/VNU_123/30106
Detection of the sul1, sul2, and sul3 genes in sulfonamide-resistant bacteria from wastewater and shrimp ponds of north Vietnam

 Mời bạn đọc vào xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30104
HIV-positive mothers in Viet Nam: using their status to build support groups and access essential services

http://repository.vnu.edu.vn/handle/VNU_123/30102
Xu hướng đồng nhất hóa và bản địa hóa của thói quen, phong tục, tập quán trong quá trình giao lưu văn hóa: nghiên cứu trường hợp các dân tộc Tây Nguyên

Mời bạn xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/24430
Twostep-by-twostep PIRK-type PC methods with continuous output formulas
http://repository.vnu.edu.vn/handle/VNU_123/30099
Magnetic Relaxation Behavior in Nd0.5Sr0.5MnO3: Observation of Negative Imaginary Component of ac Magnetic Susceptibility

 Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30098
Effects of carbon supports on Pt nano-cluster catalyst

 Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30095
The role of ligands in controlling the electronic structure and magnetic properties of Mn-4 single-molecule magnets

 Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/30093