This study on artificial propagation of the Asian painted frog (Kaloula pulchra) was conducted to evaluate the reproductive efficiency of LH-RHa stimulation. The experiment samples were randomized into 4 different dosage groups with LH-RHa, including 60, 80, 100 and 120µg/kg of body weight, and each trial was repeated four times. The results showed that the appropriate dose for Asian painted frog reproduction was the 60mg/kg of LH-RHa (treatment 1). Some reproductive parameters were documented on treatment 1 including: latencytime (5.2 ± 0.65 hours at 29.2 ± 0.170C), spawning rate (91.8 ± 8.25%), fecundity (47.866 ± 2.377 eggs per kg of female), fertilization rate (96.8 ± 0.63%), hatching time (16.2 ± 1.23 hours at 29.2 ± 0.17oC), hatch ing rate (96.6 ± 1.03%), and metamorphosis duration (14.5 ± 0.2 days at 30.5 ± 0.31oC). The average survival rate of the froglets in the treatment 1 group during 30 days of nursing was at 26.7 ± 1.33%. Moreover, this is one of the first preliminary studies about propagation of the Asian painted frog (Kaloula pulchra) in Vietnam.

This study assessed phytoplankton community composition variation under two discrete salinity intrusion rate experiments. Experiment 1 simulated salinization under short-term, natural tidally induced rates of salinity change typical of the Mekong Delta, Vietnam (0–30‰ in 6 h), while Experiment 2 simulated salinization under a longer, more gradual rate of salinity change (0–30‰ at 5‰ increase per week). Phytoplankton community composition was, overall, more abundant following prolonged salinity change (Experiment 2) than rapid, tidally-induced salinity change (Experiment 1). Under both experimental conditions phytoplankton species number and density varied with changes in salinity, indicating a strong effect of salinity regardless of its rate of change. At the end of the salinity acclimation, Cyanobacteria, Chlorophyta, Euglenophyta and Bacillariophyta were all most abundant at a salinity of 5‰ after a short-term tidally simulated change in salinity, but with a longer, more gradual change in salinity, the abundance of different groups varied with salinity; With a longer, more gradual change in salinity, Chlorophyta was most abundant at 5–10‰ salinity, while Cyanobacteria, Euglenophyta and Bacillariophyta were all most abundant at a salinity of 5‰. The species composition in treatments of less than 10‰ had high similarity with the freshwater environment while treatments of 30‰ (Experiment 1) and 25‰ (Experiment 2) had high similarity with the natural seawater environment. This study demonstrates the utility of mesocosm experiments for understanding phytoplankton community composition variation in natural aquatic ecosystems under rapid and prolonged saline intrusion rates and predicting associated impacts on food webs in natural water bodies and aquaculture systems.

In this paper, a novel single phase second order sliding mode controller (SPSOSMC) is proposed for the mismatched uncertain systems with extended disturbances and unknown time-varying delays. The main achievements of this study consist of three tasks: 1) a reaching phase in conventional sliding mode control (CSMC) technique is removed to ensure the global stability of the system; 2) an influence of the undesired high-frequency oscillation phenomenon in control input is vanished; 3) an exogenous perturbation is generally extended to the k-order disturbance of state variable. Firstly, a single phase switching manifold function is defined to eliminate the reaching phase in CSMC. Secondly, an unmeasurable state variable is estimated by using the proposed reduced-order sliding mode observer (ROSMO) tool. Next, a SPSOSMC is built based on the help of ROSMO tool and output information only. Then, a sufficient condition is established by employing the linear matrix inequality (LMI) technique and Lyapunov function theory such that the resulting sliding mode dynamics is asymptotically stable. Finally, a numerical example is simulated via the well-known MATLAB software to validate the effectiveness of the proposed technique.This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

This study was carried out to determine the bactericidal effect of the sakae  naa’s seed extract. The experiment selected concentrations of 17, 20, 23 and 26 mL/L of seed extract per liter of water to assess resistance on Vibrio parahaemolyticus, and BKC chemical (concentration of 0.5 mg/L) was chosen control treatments. The results showed that the killing ability on V. parahaemolyticus of the extract from sakae naa’s seed has gradually increased with the rising-concentration and the period of 2-10 hours after using. At a concentration of 26 mL/L, the extract of seeds gave the highest abilities to kill V. parahaemolyticus (93.8%) at 2 hours and 95.9% at 10 hours after using. In contrast, killing abilities on V. parahaemolyticus of BCK were highest at 2 hours after using (96.1%) and gradually decreased by time to time. The extracts from the seeds of sakae naa (at 26 mL/L of concentration) gave the killing ability on V. parahaemolyticus was equivalent to those of BKC at 0.5 mg/L of concentration.