Vietnam Academy of Science and Technology: Journals Online
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Effect of bias voltage and carrier gas on the hydrogen gas-sensing properties of tungsten oxide nanobeads
No full textWe investigated the effect of bias voltage and carrier gas on the hydrogen sensing performance of tungsten oxide nanobeads. The tungsten oxide nanobeads were prepared by a template-assisted method followed by calcination. The porous single walled carbon nanotube thin film was used as sacrificed template for the deposition of tungsten, followed by thermal calcination at high temperature to oxidize W into WO3 and to burn out the template. The crystal structures and morphology of the synthesized materials were characterized by X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy and Raman spectra. Hydrogen gas sensing properties were tested in air and in N2 as refence for comparison. Our results indicated that Schottky junction was formed at the interface of WO3 and Pt electrodes. The sensor operated under revered bias voltage processed excellent hydrogen sensing performance. In addition, the H2 sensing performance of the WO3 nanobeads is higher when measured in N2 gas as reference
Some species of macro-gastropods in the coastal zone of Khanh Hoa province
No full textFrom November 2013 to March 2014, 104 species were collected, belonging to 27 families, 58 genera of Gastropoda in coastal area of Khanh Hoa province. Some families have a large number of species such as Conidae - 15 species; Strombidae - 15 species; Cypraeidae - 10 species; Terebridae - 7 species and Muricidae - 6 species. Many species of economic value are used for food and fine arts. 11 species are listed in Vietnam Red Data Book. Besides, images and information of samples (collecting date, place of sample collection,...) are presented
SUPPORTED LIQUID MEMBRANE WITH STRIP DISPERSION FOR RECOVERING INDIUM FROM ETCHING SOLUTION OF LCD INDUSTRY: INFLUENCE OF FACTORS ON PERFORMANCE
No full textSupported liquid membrane with strip dispersion (SLMSD) is a promising process for metal recovery from e-waste or waste streams because of many advantages such as the ability to combine extraction and stripping into one single step and thus have non-equilibrium mass transfer characteristics and maximum driving force. This paper investigated the effect of important factors on SLMSD performance to recover indium from etching solution such as: pH of feed solution, extractant (Di-(2-ethylhexyl) phosphoric acid (D2EHPA)) concentration, oxalic acid concentration. It was found that 99.5 % In3+ was removed from feed solution in about 20 minutes with high concentration factor (4.5) under suitable conditions (pH 1; 0.6M Di-(2-ethylhexyl) phosphoric acid (D2EHPA), 2 wt% oxalic acid)
Vanillin conversion by aldol condensation using hydrotalcite Mg-Al and modified-Y zeolite as heterogeneous catalysts
No full textMg-Alhydrotalcite, MgO-Al2O3 mixed oxides and modified-Y zeolite (sulfated Y zeolite and copper ion-exchanged Y zeolite) were prepared and characterized by XRD, EDX and XRF techniques. These materials were used as heterogeneous catalysts in aldol condensation of vanillin and acetone.The obtained results showed that the heterogeneous acid catalysts as modified-Y zeolites were more effective than the heterogeneous base catalysts as hydrotalcite Mg-Al and MgO-Al2O3 mixed oxides in aldol condensation reaction of vanillin. The highest conversion of vanillin was 95.5% when the reaction was carried out at 120oC in 5 hours, using sulfated Y zeolite.
FISH SCALE DERIVED COLLAGEN/GINSENOSIDE RB1 BIOCOMPOSITES: PREPARATION, CHARACTERIZATION AND THEIR HEMOSTATIC ABILITY
No full textThis paper reports the characteristics and hemostatic ability of the collagen/ginsenoside Rb1 composites with different ginsenoside Rb1 content, in which, collagen was extracted from fresh water fish scales and ginsenoside Rb1 was extracted from Panax notoginseng. Glucose and glutaraldehyde were used as crosslinking agents for collagen molecules. Infrared (IR) spectroscopy and Field emission scanning electron microscopy (FESEM) were applied to assess the functional groups, interactions and morphology of the collagen/ginsenoside Rb1 composites. Glutaraldehyde exhibits a positive effect on improvement the dispersion of ginsenoside Rb1 in collagen matrix as well as on the interactions between ginsenoside Rb1 and collagen. In addition, the biocompatibility of the collagen/ginsenoside Rb1 in simulated body fluid was evaluated by ultraviolet-visible spectroscopy (UV-Vis). The obtained result shows that ginsenoside Rb1 can release well from the composite containing 1 wt.% of ginsenoside Rb1. Besides, the hemostatic ability of the composites was also tested and discussed
Nuclear Mean-Field Description of Proton Elastic Scattering by C at Low Energies
No full textNuclear reactions of proton by light nuclei at low energies play a key role in the study of nucleosynthesis which is of interest in nuclear astrophysics. The most fundamental process which is very necessary is the elastic scattering. In this work, we construct a microscopic proton-nucleus potential in order to describe the differential cross-sections over scattering angles of the proton elastic scattering by C and C in the range of available energies 14 - 22 MeV. The microscopic optical potential is based on the folding model using the effective nucleon-nucleon interaction CDM3Yn. The results show the promising use of the CDM3Yn interactions at low energies, which were originally used for nuclear reactions at intermediate energies. This could be the premise for the study of nuclear reactions using CDM3Yn interaction in astrophysics at low energies
Lithographic fabrication and spectroscopic characterization of a THz metamaterial absorber
No full textTHz metamaterial absorbers are often studied by computational techniques, where the influence of actual material parameters and fabricating limitation has not been completely understood. Here we present an experimental investigation on a far-infrared metamaterial absorber composed of a gold disk-shaped resonator, a silicon oxide spacer, and a gold film. The samples are fabricated using the UV laser lithography technique in combination with the electron-beam evaporation. The absorption feature of fabricated samples is examined by Fourier-transformed infrared spectroscopy and supported by finite integration simulations.
Assessment of fungi and viruses in Artichoke (Cynara scolymus L.) in Da Lat, Lam Dong province
No full textArtichoke (Cynara scolymus L.), a high economic value crop, was brought to Vietnam by the French in the late 19th century. The artichoke was mainly planted in Lam Dong, Lao Cai, Vinh Phuc provinces, etc. At present, the disease situation of Artichoke plants and the lack of disease-free seedlings result in insufficient source of Artichoke for producers. Artichoke plants are mainly vegetative propagation and pathogens easily transferred from mother to daughter plants. Therefore, low propagation rate and fungal infection are two main factors hindering the expansion and development of Artichoke cultivation (in Lam Dong). Therefore, studying and evaluating the situation of fungi and viruses as well as establishing the in vitro propagation procedures in order to produce high number of disease-free seedlings are urgent for the current Artichoke shortage. In this study, samples of purple and white Artichoke varieties, which suspected fungal manifestations, were collected to assessment of fungi and viruses in artichoke. In addition, in vitro propagation by cultivating apical meristem was applied to produce disease-free seedlings. The recorded results showed that, 19 strains of mold were identified on purple and white Artichoke belonged to nine genera including Mucor (M. sp., M. circinelloides, M. fragilis, M. irregularis, and M. racemosus), Alternaria (Alternaria sp., A. alterinata, A. gaisen, A. tenuissima, and A. tillandsiae), Fusarium (F. acuminatum and F. solani), Cylindrobasidium (Cylindrobasidium sp1 and Cylindrobasidium sp2), Actinomucor elegans, Curvalaria clavata, Plectosphaerella oligotrophica, Phoma herbarum, Rhizomucor variabillis; meanwhile, the Tomato mosaic virus (ToMV) was isolated only purple Artichoke. Shoot explants obtained from apical meristem culture were completely disease-free and used for micropropagation at the next stage
Contributions to Developments of Photoelectron Spectroscopy and X-ray Absorption Fine Structure Applied to Materials Studies
No full textThis work reviews the contributions of author to the developments and applications of Photoelectron Spectroscopy (PES) and X-ray Absorption Fine Structure (XAFS) to materials studies. Focusing on Angle resolved PES (ARPES) the energy distribution is discussed for angle-resolved photoemission from valence bands of single crystals. The important influence of the spectrometer angle of acceptance on the results of X-ray PES (XPS) is investigated in detail. The Plane Density of States (PDOS) is introduced as a new property of the electronic structure. Most meaningful contributions to XAFS consist of the developments of multiple-scattering and anharmonic XAFS theory. Anharmonic correlated Einstein model (ACEM) and anharmonic correlated Debye model (ACDM) have been derived to obtain Debye-Waller factors (DWF) presented in terms of cumulant expansion which describe the thermodynamic properties and anharmonic effects in XAFS of substances contributing to their accurate structural determination. The anharmonic effective potential (AEP) procedure and first shell near neighbor contributions approach have developed to include many-body effects in the one-dimensional model by a simple measure. Based on DWFs a thermodynamic lattice theory has been derived for studying melting curve and eutectic points of binary alloys. Several applications of the derived methods are performed and the good agreement of the calculated results with experiment illustrate the advantages and efficiencies of the achieved developments