Tạp chí Phát triển Khoa học và Công nghệ Đại học Quốc gia Thành phố Hồ Chí Minh

Geomechanics applications play an important role in both drilling and production of oil and gas field. There are many important properties such as Unconfined compression strength (UCS), Poison ratio (PR), Internal Friction Coefficient (IF) and Porosity (PHIE) need to be estimated properly. To estimate these properties, there are many methods that can be used but geostatistics has more advantages. This research presents geomecanical propertiesfor two offset wells according to experiment relations existing. Then, variogramand spatial continuity will be analyzed. The Ordinary-Kriging (OK) methods will be used to interpolatethe properties in the cross section between two offset wells and then for a planned well. The predicted properties were compared with the actual measured data to find the linear correlation coefficient. Most of these values arenearly 1. As a result, the quality of the modelbuilt could be practically accurate and reliable to predict geomechanical properties for planned wells used in wellbore stability, sanding studies.

Bacterial strain SH1 was isolated from entomopathogenic nematodes (EPN) Heterorhabditis indica CP16 released from insect cavaders (Spodoptera litura). Their identification by API 20E Kit as well as by 16S rDNA sequencing showed that it belongs to the species Serratia marcescens. The isolate expressed the toxicity to Spodoptera litura. In the injection assay more than 65 % insects were killed after 10 h at 23 cfu/insect; in the ingestion assay (droplet on leaf surface), more than 50 % insects were killed after 72 h at 170 cfu/cm2. The red pigment produced by the isolate SH1 was confirmed to be one of its secondary metabolites – prodigiosin based on its color, UV/VIS spectra và ESI-MS results. When injected to Spodoptera litura at a dose of 422 ng/insect, the active compound killed approximately 65 % insects after 10 h of treatment, and in the ingestion assay (droplet on the leaf surface) at a dose of 27.66 ng/cm2 killed approximately 90 % insects after 120 h of treatment.

Indian neem oil, petroleum ether extract (laboratory neem oil), ethanol and methanol extracts of neem seed kernels at 250 ppm - 4000 ppm concentrations were investigated us antifungal agents on the phytopathogenic fungus Fusarium oxysporum. All treatments exhibit the antifungal activity on phytopathogenic fungus Fusarium oxysporum with different activities depending on the type of treatment materials and concentrations. The highest antifungal activity is at 4000 ppm concentration. The ICso values showed that the ethanol extract has the highest antifungal activity on the growth of the fungus Fusarium oxysporum. Besides, the purified azadirachtin at 4000 ppm was also used for investigating the antifungal activity on fungus Fusarium oxysporum and purified azadirachtin exhibited a very little inhibition on the radial growth of this fungus. It probably showed that the antifungal activity of neem seed kernel extracts are the synergistic effect of many compounds other than azadirachtin.

Introduction: The formation of G-quadruplex plays a key role in many biological processes. Therefore, visualization of G-quadruplex is highly essential for design of G-quadruplex-targeted small molecules (drugs). Herein, we report on an engineered fluorescent protein probe which was able to distinguish G-quadruplex topologies. Methods: The fluorescent protein probe was generated by genetically incorporating yellow fluorescent protein (YFP) to RNA helicase associated with AU-rich element (RHAU) peptide motif. Results: This probe could selectively bind and visualize parallel G-quadruplex structure (T95-2T) at high affinity (Kd~130 nM). Visualization of the parallel G-quadruplex by RHAU-YFP could be easily observed in vitro by using normal Gel Doc or the naked eye. Conclusion: The YFP probe could be encoded in cells to provide a powerful tool for detection of parallel G-quadruplexes both in vitro and in vivo.  

In this study, the effect of Galactooligosaccharide (GOS) (0% và 2% w/v) on microencapsulated L.casei in whey protein 10% (w/v) and maltodextrin 5% (w/v) by spray dry method were investigated. The physical characterization included analysis of morphology, particle size. The viable cell counts of the microcapsule were determined during storage for 50 days at 10oC and in simulated gastric fluid (SGF) and intestinal fluid (SIF). All microcapsules with (WMG sample) or without GOS (WM sample) in this study showed similar morphology and particle size, between 3 to 11µm. There no differences between WMG and WM sample in cell viability were observed. For spray dry conditions tested in this work the cell viable yield with WM sample about 86.14% whereas for WMG sample about 86.78%. The viability of the microcapsules in WMG and WM were reduced about 0.44 and 0.63 log(CFU/g), respectively and remained > 6 log(CFU/g) after 2 hour in SGF or 4 hour in SIF incubating. Microcapsules made by spray dry method with whey protein 10% (w/v) and maltodextrin 5% (w/v) as encapsulating which enhancing L.casei survival, maltodextrin’s role not only as a wall material in microencapsulation but also as a prebiotic potential, eventually leading to added GOS was not necessary.

Face recognition, that has a lot of applications in modern life, is still an attractive research for pattern recognition community. Due to the similarity of human face, face recognition presents a significant chalenge for pattern recognition researchers. Modified Hausdorff distance (MHD) is a low computational cost while giving high accuracy for face recognition. In this paper, a modification of MHD (MMHD) is proposed. By applying the ratio of high confident into the calculation of the distance between images, the MMHD gives higher accuracy in face recognition in comparing with MHD method. The MMHD method also gives higher performance than MHD method in face recognition in various non-ideal conditions of image: 1) varying lighting conditions, 2) varying face expressions and 3) varying of poses.

GIS with the ability in analysing-composing-visualizing is a neccessary means of teaching, studying and researching in the field of geology. But geological maps are too complex to be digitized on digitizer, that blocks the application GIS in teaching geological materials. Wingis - GIS software can automatically digitizes the image information and can work with other GIS software. This primary experiment result open the ability of improving teaching method for the traditional geological materials.

Multiphase drives are more and more used in specific applications leading to a necessity of control strategy development. This paper presents the Generalized Vectorial Formalism (GVF) theory to control multiphase series-connected permanent magnet synchronous motors (PMSM) fed by one voltage source inverter (VSI). Based on a decomposition of multiphase machine, a proposed control strategy has been achieved. Some experimental results are given to illustrate this control method.

Carbon aerogel was obtained by pyrolysis of organic aerogel by ambient pressure drying technique. The effect of pyrolysis conditions on characteristics of carbon aerogel such as density, specific surface area and conductivity was studied. The properties and structure of carbon aerogel samples were investigated by nitrogen adsorption, four-point probe method and XRD diffraction. The results showed that carbon aerogel had structure between amorphous and graphite state. The highest specific surface area was 800 m2/g at pyrolysis temperature of 700oC. The pore-size was distributed in microporous, with the maximum total pore volume of 0.44 cm3/g. The electrical conductivity of carbon aerogel was highest at pyrolysis temperature of 800-900oC with the value in the range of 1.744-1.923 S/cm.

We have developed a system for supporting the query in a database of DNA sequences. We would like to develop a system for grouping similar DNA sequences into clusters based on frequent motifs or motif phrases. Each cluster is represented by a cluster feature vector of maximal frequent motifs or motif phrases). A motif tree of cluster features is built. The similarity search will be divided into two steps. Firstly, the system will search the clusters which have the high matching with the query pattern. Secondly, the traditional matching techniques (FASTA or BLAST) will be used for matching between pattern and a small number of DNA sequences of selected cluster.