Science and Technology Development Journal 2019-11-18T12:53:06+00:00 Phuc Van Pham Open Journal Systems A high dynamic range imaging algorithm: implementation and evaluation 2019-11-18T12:53:04+00:00 Vu Hong Son <p>Camera specifications have become smaller and smaller, accompanied with great strides in technology and thinner product demands, which have led to some challenges and problems. One of those problems is that the image quality is reduced at the same time. The decrement of radius lens is also a cause leading to the sensor not absorbing a sufficient amount of light, resulting in captured images which include more noise. Moreover, current image sensors cannot preserve whole dynamic range in the real world. This paper proposes a Histogram Based Exposure Time Selection (HBETS) method to automatically adjust the proper exposure time of each lens for different scenes. In order to guarantee at least two valid reference values for High Dynamic Range (HDR) image processing, we adopt the proposed weighting function that restrains random distributed noise caused by micro-lens and produces a high quality HDR image. In addition, an integrated tone mapping methodology, which keeps all details in bright and dark parts when compressing the HDR image to Low Dynamic Range (LDR) image for display on monitors, is also proposed. Eventually, we implement the entire system on Adlink MXC-6300 platform that can reach 10 fps to demonstrate the feasibility of the proposed technology.</p> <p>&nbsp;</p> 2019-08-07T00:00:00+00:00 ##submission.copyrightStatement## Electrochemical performance of sulfone-based electrolytes in sodium ion battery with NaNi1/3Mn1/3Co1/3O2 layered cathode 2019-11-18T12:52:56+00:00 THANH DUY VO AN LE BAO PHAN BINH THANH TRAN NAM PHAM PHUONG LE PHUNG MY LOAN LE <p><strong>Introduction</strong>: Sulfolane (SL), having an edge of low melting point over other sulfones, has been adopted as an electrolyte co-solvent for lithium-ion battery (LIB), as it exhibits high stability against oxidation and combustion while not causing much side effects to the battery electrochemistry. It is therefore expected that SL may serve as a safety-enhancing agent in sodium-ion battery (SIB). To evaluate the effect of SL content on the behavior of common carbonate-based sodium electrolytes as well as the compatibility of SL-based electrolytes with NaNi1=3Mn1=3Co1=3O2 (NaNMC) cathode, mixtures of 0, 10, 20, 30 or 50% vol. SL and each of the following, EC:PC 1:1 vol. (EP11), EC:DMC 1:1 vol. (ED11), EC:PC:DMC 1:1:3 vol. (EPD113) and EC:PC:DMC 3:1:1 vol. (EPD311), with or without 1M NaClO4, were studied with regard to both inherent properties and performance in NaNMC half-cells.</p> <p><strong>Methods</strong>: Solvent flammability was evaluated via the self-extinguishing time (SET) and ignition time indexes. Conductivity and viscosity were respectively measured by Electrochemical Impedance Spectroscopy (EIS) and Ostwald method. Electrochemical techniques, i.e. Cyclic Voltammetry (CV) and Galvanostatic Cycling with Potential Limitation (GCPL), were used to test the sodium-ion battery performance.</p> <p><strong>Results</strong>: A moderate amount of SL (typically below 30% vol.) proved to enhance both electrolyte non-flammability and self-extinguishing behavior, while maintaining an acceptable compromising rate in viscosity and conductivity. Amongst 30%-SL electrolytes, EPD311-based ones allow the best Na+ diffusion when combined with NaNMC cathode in sodium half-cell configuration. The corresponding system gives satisfactory performance: initial specific capacity of 97 mAh.g<sup>-1</sup>, 92% capacity retention, and above 90% reversibility after 30 cycles at C/10 rate.</p> <p><strong>Conclusion</strong>: SL can be used as a stabilizing co-solvent for SIB, but its content should be limited to below 30% vol. to ensure its effectiveness.</p> 2019-10-03T22:34:18+00:00 ##submission.copyrightStatement## Frequency distribution of dental caries disease among the local community of Harichand 2019-11-18T12:53:01+00:00 Haroon Haroon Tauseef Ahmad Muhammad Khan Inamullah Inamullah Arif Jan Hui Jin <p>A cross-sectional study was designed to determine the dental caries disease and associated risk factors among the study subjects in Harichand, Pakistan. A total of 150 patients were investigated, of which male to female percentage was (77%) and (23%) respectively. The maximum tooth decay (33%) was found in the age (years) of 21-30. The results showed that decayed and missing teeth (DMT) were (57%), followed by decayed, missing and filled teeth (DMFT) (27%) and filled teeth (FT) (16%). Most of the patients were suffering from score 6, (30%). The DMT and score 6 was recorded high among the study subjects in Harichand. This study will update the epidemiology of dental caries diseases, increase awareness, and provide the base line information for future research and intervention. Further studies are recommended on large scale.</p> 2019-08-20T00:00:00+00:00 ##submission.copyrightStatement## Homology of Borel Subgroup of SL(2,\mathbb{F}_p) 2019-11-18T12:53:03+00:00 Bui Anh Tuan Bao Quoc Vo <p>In this paper we compute the integral homology of the Borel subgroup $B$ of the special linear group $SL(2,\mathbb{F}_p), p$ is a prime number. Arcoding to Adem \cite{AJM} these are periodic groups. In order to compute the integral homology of $B,$ we decompose it into $\ell-$ primary parts. We compute the first summand based on Invariant Theory and compute the rest summand based on Lyndon-Hochschild-Serre spectral sequence. We assume that $p$ is an odd prime and larger than $3.$</p> 2019-08-18T22:18:56+00:00 ##submission.copyrightStatement## The influence of thickness on ammonia gas sensitivity of reduced graphene oxide films 2019-11-18T12:53:06+00:00 Tran Quang Nguyen Huynh Tran My Hoa Tran Quang Trung <p>Graphene is a single carbon layer in a two-dimensional (2D) lattice. Its delocalized π bonds give rise to unique electronic properties, but these π bonds are easily influenced by the environment. Meanwhile, many publications present that the sensitivity of graphene is not only necessarily intrinsic to this material but also by external defect. In this study, we produced reduced Graphene Oxide (rGO) sensors based on random rGO plates. We analyzed the ammonia (NH3 ) sensitivity of such sensors as a function of thickness of rGO films (in terms of change in transparence) at room temperature. When the thickness of rGO films decreased, a maximum response was observed for the thinnest rGO film (the transparence was 84 %), with a sensitivity up to 38 %. Our results suggest that the dependence of NH3 sensitivity on rGO films thickness is dictated by the fully exposed surface area for thinnest films and by 2D charge carrier hopping through edge defects.</p> <p>&nbsp;</p> 2019-08-03T00:00:00+00:00 ##submission.copyrightStatement## The research determines appropriate parameters in the synthesis process of syringic acid grafted chitooligosaccharides 2019-11-18T12:52:59+00:00 Hoai Van Bui Dai-Nghiep Ngo <p><strong>Introduction</strong>: The aim of this study is to determine appropriate parameters in the synthesis of syringic acid onto chitooligosaccharides (COSs) with an ascorbic acid/hydrogen peroxide redox pair in order to obtain the derivative with the highest grafting degree.</p> <p><strong>Methods</strong>: In this study, syringic acid grafted COSs, catalysed by an ascorbic acid/hydrogen peroxide redox pair were investigated. The synthesis conditions were investigated, including the mass ratio between syringic acid and COSs, pH, temperature and synthesis time. Characteristics of the derivative were evaluated by Thin Layer Chromatography (TLC), Ultraviolet-Visible (UV-vis) and Fourier Transform Infrared (FT-IR) spectroscopy. The activities of COSs and derivative were evaluated by antimicrobial ability.</p> <p><strong>Results</strong>: The results showed, that the best conditions for the synthesis were the mass ratio between syringic acid and COSs at 0.5:1, pH 5, temperature 27<sup>o</sup>C, for 6 hours with grafting degree at 32%. The TLC assay showed, that free ascorbic acid and syringic acid are not present in the product. The UV-vis and FT-IR data confirmed, that syringic acid was successfully conjugated onto COSs. Furthermore, the antibacterial assay showed that syringic acid grafted onto COSs had minimum inhibitory concentration against foodborne pathogenic bacteria at 1%.</p> <p><strong>Conclusion</strong>: The syringic acid onto chitooligosaccharides were successfully synthesized by free radical mediated grafting method with an ascorbic acid/hydrogen peroxide redox pair. The grafting degree of syringic acid onto COSs was greatly affected by many factors, including COSs, syringic acid, pH, as well as temperature and time of reaction. Moreover, the new derivative showed enhanced antibacterial capabilities, as compare to free COSs.</p> <p>&nbsp;</p> 2019-08-22T00:00:00+00:00 ##submission.copyrightStatement## Hydrophobic Property of (R)-3 Amidinophenylalanine Inhibitors Contributes to their Inhibition Constants with Thrombin Enzyme 2019-11-18T12:52:54+00:00 Hien Van Nguyen Van Thi Bich Pham Hao Minh Hoang <p><strong>Introduction</strong>: Thrombin is the key enzyme of fibrin formation in the blood coagulation cascade. Thrombin is released by the hydrolysis of prothrombinase which is generated from factor Xa and factor Va in the presence of calcium ion and phospholipid. The inhibition of thrombin is of therapeutic interest in blood clot treatment. Currently, potent thrombin inhibitors of (<em>R</em>)-3- amidinophenylalanine, derived from benzamidine-containing amino acid, have been developed so far. In order to quantitatively express a relationship between chemical structures and inhibition constants (K<sub>i</sub> with thrombin enzyme in a data set of (<em>R</em>)-3-amidinophenylalanine inhibitors), we developed a quantitative structure-activity relationship (QSAR) modeling from a group of 60 (<em>R</em>)-3- amidinophenylalanine inhibitors.</p> <p><strong>Methods</strong>: A database containing chemical structures of 60 inhibitors and their Ki values was put into molecular operating environment (MOE) 2008.10 software, and the two-dimensional (2D) physicochemical descriptors were numerically calculated. After removing the irrelevant descriptors, a QSAR modeling was developed from the 2D-descriptors and K<sub>i</sub> values by using the partial least squares (PLS) regression method.</p> <p><strong>Results</strong>: The results showed that the hydrophobic property, reflected through <em>n</em>-octanol/water partition coefficient (P) of a drug molecule, contributes mainly to K<sub>i</sub> values with thrombin.The statistic parameters that give the information about the goodness of fit of a 2D-QSAR model (such as squared correlation coefficient of R2 = 0.791, root mean square error (RMSE) = 0.443, cross-validated Q2 cv = 0.762, and cross-validated RMSEcv = 0.473) were statistically obtained for a training set (60 inhibitors). The R2 and RMSE values were obtained by using a developed model for the testing set (9 inhibitors) ; the total set has statistically significant parameters. Furthermore, the 2D-QSAR modeling was also applied to predict the K<sub>i</sub> values of the 69 inhibitors. A linear relationship was found between the experimental and predicted pK<sub>i</sub> values of the inhibitors.</p> <p><strong>Conclusion</strong>: The results support the promising application of established 2D-QSAR modeling in the prediction and design of new (<em>R</em>)-3-amidinophenylalanine candidates in the pharmaceutical industry.</p> <p>&nbsp;</p> 2019-10-15T12:57:16+00:00 ##submission.copyrightStatement## Triterpenoid Glycosides from Olax imbricata 2019-11-18T12:52:58+00:00 Nga Thi Vo Suong Thi Minh Huynh Huong Thi My Nguyen Huy Thuc Duong Phung Kim Phi Nguyen <p><strong>Introduction</strong>:<em> Olax imbricata</em>, owning antibacterial, antioxidant, and anti-inflammatory activities, has been investigated as one of traditional diabetic plants in Vietnam. In our previous publications on <em>Olax imbricata</em>, the structure analysis of the isolated compounds were reported, including two phenolic compounds, three phenolic glycosidic compounds, a sesquiterpenoid tropolone and 1,2,3,4-tetrahydronaphthalene derivatives. This article described the isolation and structure elucidation of three triterpenoid glycosides isolated from the methanol extract of Olax imbricata growing in Phu Yen province. Additionally, the evaluation of inhibitory activity for a-glucosidase was performed on a pure compound.</p> <p><strong>Method</strong>: The methanol extract of this plant applied the chromatographic techniques, including thin-layer chromatography and silica gel column chromatography, led to the isolation of three pure compounds. The structures of three isolated compounds were elucidated by the spectroscopic data, including 1D and 2D NMR spectra in a combination of HRESIMS, and the sugar moieties were elucidated by acid hydrolysis. The a-glucosidase inhibitory assay was applied to a pure compound by the colorimetric method.</p> <p><strong>Results</strong>: Three triterpenoid glycosides, namely 3-O-a-L-rhamnopyranosyl-(1-&gt;4)-b -D-glucopyranosyl-(1-&gt;3)-6′- O-ethyl-b -Dglucuronyl oleanolic acid (<strong>1</strong>), oleanolic acid 28-O-b -D-glucopyranoside (<strong>2</strong>) and spergulacin (<strong>3</strong>) were isolated and elucidated. The compound <strong>2</strong> showed its strong potentiala-glucosidase inhibitory activity with the IC<sub>50</sub> value of 56.15+/-1.31 mM.</p> <p><strong>Conclusion</strong>: Among them, compound 1 is a new one, the compounds <strong>2</strong> and <strong>3</strong> were isolated for the first time from the genus Olax. The compound 2 exhibited the potential a-glucosidase inhibition activity, contributing to demonstrating the diabetes treatment ability of <em>Olax imbricata</em> in the folklore.</p> <p>&nbsp;</p> 2019-09-02T00:00:00+00:00 ##submission.copyrightStatement## Evaluating the applicability of a low-cost sensor for measuring PM2.5 concentration in Ho Chi Minh city, Viet Nam 2019-11-18T12:52:57+00:00 Chi Doan Thien Nguyen Hien Thi To <p><strong>Introduction</strong>: Continuous monitoring provides real-time data which is helpful for measuring air quality; however, these systems are often very expensive, especially for developing countries such as Vietnam. The use of low-cost sensors for monitoring air pollution is a new approach in Vietnam and this study assesses the utility of low-cost, light-scattering-based, particulate sensors for measuring PM<sub>2.5</sub> concentrations in Ho Chi Minh City.</p> <p><strong>Methods</strong>: The low-cost sensors were compared with both a Beta attenuation monitor (BAM) reference method and a gravimetric method during the rainy season period of October to December 2018.</p> <p><strong>Results</strong>: The results showed that there was a very strong correlation between two low-cost sensors (R = 0.97, slope = 1.0), and that the sensor precision varied from 0 to 21.4% with a mean of 3.1%. Both one-minute averaged data and one-hour averaged data showed similar correlations between sensors and BAM (R<sup>2</sup> = 0.62 and 0.69, respectively), while 24-hour averaged data showed excellent agreement (R<sup>2</sup> = 0.95, slope = 1.05). In addition, we also found a strong correlation between those instruments and a gravimetric method using 24-hour averaged data. A linear regression was used to calibrate the 24-hour averaged sensor data and, once calibrated, the bias dropped to zero.</p> <p><strong>Conclusion</strong>: These results show that low-cost sensors can be used for daily measurements of PM<sub>2.5</sub> concentrations in Ho Chi Minh City. The effect of air conditions, such as temperature and humidity, should be conducted. Moreover, technical methods to improve time resolution of lowcost sensors need to be developed and applied in order to provide real-time measurements at an inexpensive cost.</p> <p>&nbsp;</p> 2019-09-30T00:00:00+00:00 ##submission.copyrightStatement##