VOLATILE COMPOSITION, ANTIOXIDANT PROPERTY AND ANTIMICROBIAL ACTIVITIES AGAINST FOOD-BORNE BACTERIA OF VIETNAMESE THYME (Thymus vulgaris L.) ESSENTIAL OIL

The essential oil (EO) obtained from the leaves of the thyme (Thymus vulgaris L.) grown in Vietnam was found to contain thymol (39.79%), cymene (17.33%), and γ-terpinene (13.45%) as the main volatile components. The antimicrobial activities of this oil were screened against several food-borne bacteria and fungi species. Significant growth inhibition effects against food-borne bacteria Escherichia coli, Staphylococcus aureus, Bacillus cereus, and Salmonella Typhimurium were observed using the standard disc diffusion method. Thyme EO showed the antibacterial effect against all the test pathogenic strains with the inhibition zones were 23.3 ± 0.4 mm, 24.7 ± 0.4 mm, 29.0 ± 0.7 mm, 32 ± 0.7 mm in diameter against B. subtilis,  E. coli, S. Typhimurium and S. aureus, respectively. The minimum inhibitory concentration (MIC) determined by micro-dilution method in MHB liquid medium was 1.56 µl/ml. The bactericidal concentrations (MBC) was 3.13 µl/ml for three isolates from B. subtilis,  E. coli, and S. aureus, while the MBC tested for S. typhi was 1.56 µl/ml. The antifungal properties of the thyme EO were also determined in this study against three important pathogenic fungi such as Candida albicans, Rhizoctonia solani and Fusarium oxysporum with the inhibition zones ranging approximately from 23.20 ± 0.06 to 44.10 ± 0.03 mm. On the other hands, the results also showed the antioxidant activity of Vietnamese thyme EO and suggested that thyme EO can be applied in food industries as natural flavoring preservatives/additives to control food spoilage and food born bacteria and fungi

PREMILINARY RESEARCH ON ARSENIC POLLUTION OF SURFACE AND GROUND WATER IN TRA NANG GOLD EXPLOITATION REGION-LAM DONG PROVINCE AND CAO LANH TOWN-DONG THAP PROVINCE

Joint Research on Environmental Science and Technology for the Eart

Corrosion protection of carbon steel by an epoxy resin containing organically modified clay

This study focusses on the use of montmorillonite clay (MMT) treated with an organic compound (aminotrimethylphosphonic acid (ATMP)) and dispersed in an epoxy resin to improve corrosion protection of carbon steel. X-ray diffraction was performed to verify that the individual silicate layers were separated and dispersed in the epoxy resin. Corrosion resistance of the coated steel was evaluated by electrochemical impedance spectroscopy (EIS) and local electrochemical impedance spectroscopy (LEIS). Three systems were tested: the epoxy clear-coat, the epoxy resin containing 2 wt.% clay and the epoxy resin containing 2 wt.% clay modified byATMP (ATMP-modified clay). From conventional EIS, it was shown that the incorporation of clay or ATMP-modified clay in the epoxy matrix significantly improved the barrier properties of the coating. The corrosion resistance of the carbon steel coated by the epoxy resin containing ATMP-modified clay was higher than that obtained for the system containing non-treated clay. Local electrochemical measurements performed on scratched samples revealed the inhibitive role of ATMP at the carbon steel/coating interface

Understanding Problems of High Polymer Demand in Sludge Dewatering for Better Sludge Management

University of Technology Sydney. Faculty of Engineering and Information Technology.High polymer demand in sludge conditioning and dewatering is an unavoidable aspect of the water industry. Understanding interaction mechanisms between sludge particles and conditioning polymers in sludge dewatering is necessary to: firstly, maximize dewatered cake solids content; and secondly, to minimize polymer demand for conditioning. , two scientific methodologies, namely the ‘y-intercept’ concept and Higgins modified centrifugal technique (Higgins MCT) were used to identify the optimum polymer demand and type for effective conditioning and dewatering. Results from the ‘y-intercept’ concept show that a large amount of polymer required during conditioning of anaerobically digested sludge (ADS) is mainly due to the neutralization of soluble biopolymers or extracellular polymeric substances (EPS) in sludge. In contrast, conditioning of aerobically digested sludge (AEDS) and waste activated sludge (WAS) is mostly controlled by a polymer bridging mechanism. The results indicated that, in order to achieve maximum dewatering performance with minimum conditioning polymer requirement, high charge density polymers are suitable for ADS while branched (or cross-linked) polymers can be used for AEDS and WAS. In addition, the new lab-scale technique, Higgins MCT, was successfully established and implemented for measuring cake solids content achievable by centrifuge and determining the optimum polymer demand (OPD). The Higgins MCT also helped to understand the relationship between digestion, conditioning, and dewatering. It has been demonstrated that excess amounts of soluble EPS released in digestion can lead to high polymer demand for sludge dewatering. Elucidation of how much soluble EPS contribute to polymer demand for conditioning is important to identify pathways to minimize chemical usage without compromising dewatering performance. Thus, , a simple and unique yet effective method for quantifying the contribution of soluble EPS to polymer requirement was developed. This was achieved through measuring the absorbance of the supernatant derived from conditioned digested sludge at the 191.5 nm wavelength. In addition, the role of tightly bound EPS in determining the dewatering performance of digested sludges was also investigated. Specifically, the study examined ADS and AEDS from seven full-scale wastewater treatment plants (WWTPs). Results showed that the concentrations of soluble EPS in the sludges varied between 92–1148 mg/L. The EPS in ADS was much higher than those of AEDS. Experimental results also demonstrated that higher amounts of polymers were wasted in “parasitic” reactions with soluble EPS. For example, for ADS, it was as high as 40–86% of the cationic polymer dose) while for AEDS, it was less in the range of 25–33%. The residual cationic polymer left in solution, after the parasitic reactions, was substantial and varied between 35–254 mg/L. Despite that, zeta potential values of dewatered sludge cakes remained negative, i.e. between -24 – -35 mV. This indicated that the residual soluble cationic polymers would not have been absorbed on the negatively charged sludge particles. This explained the relatively poor performances of the dewatering in the plants studied. The study results also suggested that the tightly bound EPS attached to the sludge particles would be responsible for the low dewatering performance. It is postulated that the tightly bound EPS would gelify and immobilize the water surrounding the sludge particles. , inter-relationships between wastewater and sludge treatment, specifically among Enhanced Biological Phosphorus Removal (EBPR), anaerobic digestion, and dewatering, were investigated to identify feasible approaches to reduce both chemical and transportation costs for the EBPR plants. EBPR and non-EBPR WWTPs were compared in this study in order to determine the effects of EPBR and anaerobic digestion (AD) on sludge conditioning and dewatering. Experimental results show that EPBR and AD resulted in significant decreases in divalent cations and generation of soluble EPS, leading to a deterioration of bio-flocculation of ADS particles and requiring extra polymer dose for effective ADS conditioning and dewatering. In the two-stage AD, acid phase led to significant increases in concentrations of soluble biopolymers (more than double) due to hydrolysis reactions which converse non-soluble biopolymers to soluble organic compounds. Therefore, proper control of the acid phase can help reduce the content of soluble EPS to an optimum value that could favor both flocculation while minimizing the chemical cost for conditioning

Perinatal outcome of preterm cesarean section in a resource-limited centre: A comparison between general anaesthesia and subarachnoid block

Background: The relationship between perinatal outcome and anesthetic technique for preterm cesarean sections has not been explored in South Eastern, Nigeria.Objective: The objective of the following study is to evaluate perinatal outcome in preterm cesarean sections conducted under general anesthesia (GA) and subarachnoid block (SAB) with the aim to ascertain any difference in outcome between the two methods.Materials and Methods: Aretrospective observational study of consecutive preterm cesarean deliveries at the University of Nigeria Teaching Hospital from May 1999 to April 2008. Data entry and statistical analysis utilized the SPSS statistical package for the social sciences, 2008 version 15.0 for windows (SPSS Inc, Chicago IL, USA). Chi.square test was done to determine statistical significance and P . 0.05 were considered to be significant at 95% confidence interval. The delivery characteristics were compared by logistic regression analysis to ascertain any associated confounding effect on perinatal outcome in those exposed to either anesthetic technique.Results: There were 7568 deliveries and 1961 cesarean sections giving a cesarean section rate of 25.9%. A total of 236 cesarean sections were for preterm deliveries giving a preterm cesarean section rate of 3.1%. Of these, 151 women delivered under GA while SAB was used in 85 cases. The mean gestational ages for preterm cesarean sections were 33.2 ± 2.6 weeks and 33.8 ± 2.2 weeks for those who had GA and SAB respectively. The mean Apgar scores were 6.4 ± 3.1 and 7.6 ± 3.1 at 5 min for GA and SAB respectively. There were 24 stillbirths (15.9%) in cesarean deliveries done under GA and 7 stillbirths (8.2%) in women who had SAB (P = 0.09). Twenty-two (14.6%) babies delivered through GA and 14 (16.4%) delivered under SAB, died within 1 week of delivery (P = 0.7). There were more babies with low Apgar scores in parturient delivered under GA (P = 0.0004). More preterm babies delivered under SAB were discharged from the New Born Special Care Unit within 10 days of delivery (P = 0.006). Hypertensive disorders, though not statistically significant was the most common  indication for preterm cesarean delivery among those with GA and SAB. No maternal death occurred during the study period.Conclusion: The study infers a strong association between anesthetic technique and immediate Apgar scores and outcome of resuscitation following preterm cesarean section. This however, failed to translate into higher differences in perinatal mortality.Key words: General anesthesia, perinatal.outcome, preterm cesarean section, subarachnoid bloc

Overall viscoelastic properties of 2D and two-phase periodic composites constituted of elliptical and rectangular heterogeneities

International audienceThis paper presents analytical solutions for the effective rheological viscoelastic properties of 2D periodic structures. The solutions, based on Fourier series analysis, are derived first in the Laplace-Carson (LC) space for different inclusion shapes (rectangle or ellipse) and arrangements. The effective results are obtained in the form of rational functions of the LC transform variable. Two inversion methods are used to find the relaxation behavior. The first one is based on the exact inverse of the LC transform while the second approximates the overall behavior by using a Standard Linear Solid model, which yields very simple analytical formulas for the coefficients entering the constitutive equations. Results of the two methods are compared in the case of an application to real materials

Potential Usage of Rice Husk Ash-Cement Based Soil in Subbase and Base Courses in Road Construction

This paper presents an experimental study of rice husk ash-cement-based soil for layers in roadway construction. Rice husk ash (RHA) used in this study is a by-product of rice milling. In this work, twelve proportion mixes were used in this work with varying quantities of RHA (0-30%) and Portland cement blended amounts of 4, 6, 8%. The specimens were prepared by the Proctor mould method, conditioned at room temperature, and tested in soaked and unsoaked conditions. Specified curing periods of 7, 14, 28 days were applied for all types of specimens. Some engineering tests were carried out such as proctor compaction, unconfined compressive strength, splitting tensile strength, and the stiffness of stabilized soil. Test results indicated a general decrease in the maximum dry density (MDD) and increased optimum moisture content (OMC) with an increase in RHA content. Adding cement and RHA significantly improved the geotechnical properties of stabilized soils, including compressive strength, splitting tensile strength, elastic modulus. In addition, the combination of 80% soil and 20% RHA and 6% cement can be used as the optimum proportion which satisfied the grade 3 of soils stabilized with inorganic adhesive substances, chemical agents, or reinforced soil for road construction, as indicated in the current Vietnamese standard

Potential Usage of Rice Husk Ash-Cement Based Soil in Subbase and Base Courses in Road Construction

This paper presents an experimental study of rice husk ash-cement-based soil for layers in roadway construction. Rice husk ash (RHA) used in this study is a by-product of rice milling. In this work, twelve proportion mixes were used in this work with varying quantities of RHA (0-30%) and Portland cement blended amounts of 4, 6, 8%. The specimens were prepared by the Proctor mould method, conditioned at room temperature, and tested in soaked and unsoaked conditions. Specified curing periods of 7, 14, 28 days were applied for all types of specimens. Some engineering tests were carried out such as proctor compaction, unconfined compressive strength, splitting tensile strength, and the stiffness of stabilized soil. Test results indicated a general decrease in the maximum dry density (MDD) and increased optimum moisture content (OMC) with an increase in RHA content. Adding cement and RHA significantly improved the geotechnical properties of stabilized soils, including compressive strength, splitting tensile strength, elastic modulus. In addition, the combination of 80% soil and 20% RHA and 6% cement can be used as the optimum proportion which satisfied the grade 3 of soils stabilized with inorganic adhesive substances, chemical agents, or reinforced soil for road construction, as indicated in the current Vietnamese standard

What Shapes Undergraduate Students’ Satisfaction in Unstable Learning Contexts?

This paper investigates what determinants, and to what extent, they influence students’ satisfaction in unstable learning contexts. Using a national-scaled sample of Vietnamese HEIs with a sound theoretical background, we find that regardless of instabilities from external shocks, the key factors that shape students’ satisfaction are fixed by traditional norms (self-efficacy, infrastructure, lecturer) rather than occasional factors occurring from each event. We find in particular that self-efficacy is the most influential factor for students’ satisfaction and friendship is the most prominent element that enhances students’ self- efficacy. Overall, this paper enriched the literature on student satisfaction, especially during unstable contexts. Thus, it has important implications for educators and HEIs stakeholders in management planning in the time to come