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Plastic microbeads are commonly used in many personal care products and can cause adverse impacts to the environment and ecosystem. The toxicological problem with these pollutants are due to their non-biodegradable materials, which washed down the drain; end up accumulating in the aquatic system causing increased frequency and quantity of items ingested by biota. Several polymers (e.g. Polyethylene) especially those found in plastic microbeads have been reported to be in tandem with other toxic contaminants serving as a vector for their transports in the environment. Thus, the legislative ban for plastic microbeads is used in some developed countries, but many countries including Vietnam do not take any legal action. This present study aimed at potential microbead’s existence in the cosmetic market of Ho Chi Minh City (HCMC). The list and ingredients of microbeads containing personal care products (toothpaste, facial cleanser/scrubs and body wash/scrubs) have been checked. The microbeads containing PCPs are common for all explored categories, especially in toothpaste. Data from the online questionnaire survey have shown that 98% of respondents have frequently used at least one microbead containing product. Four polymers (Polyethylene, Acrylates Copolymer Styrene/Acrylates Copolymer and Acrylates/C10-30 Alkyl Acrylate Crosspolymer) have been observed in the product package of several facial cleansers and body scrubs. Thus, the potential negative impacts of this contaminant should not be ignored.

We present a numerical simulation of the beam-steering of ultrasonic guided waves in an isotropic and viscoelastic solid plate, which mimics bovine cortex. The excitation was modeled by a group of five finite-size emitters, each exercised a normal force to the bone plate. Beam steering was achieved by delaying the emitters’ firing. The simulation technique was implemented by a semi-analytical finite element scheme to compute the wave fields. At small steering angles, the simulated time-offset signals show mainly two groups of arrivals. The first group is the fast-traveling and high-frequency bulk waves and the second one is slow-traveling and low-frequency guided waves. The fast-traveling waves gradually diminish with increasing steering angles, in agreement with the excitation function of the source influence theory. The frequency-phase velocity dispersion maps also illustrate the phenomenon. The study has demonstrated that the lowest order Lamb asymmetrical mode, A 0, which is useful for bone characterization, can best be excited when the cortical bone thickness is thin, the beam angle is large, and the excited frequency is low.

In the present study, the synthesis of Mg-Al layered double hydroxide at the molar ratio of 3:1 for Mg/Al are determined. One-step hydrothermal technique with slow hydrolysis of urea at a low temperature was employed without further annealing. The study was aimed at determining the effectiveness of Congo Red dye removal in the adsorption process onto Mg-Al layered double hydroxide (LDH) with respect to the change in pH of the solution. The experiment was conducted at concentrations of a sorbent 0.04g with 100 ml of Congo Red and at six values of the reaction, i.e. pH 2.0, pH 4.0, pH 6.0, pH 8.0, pH 10, and pH 12.0. It was found that pH affects the adsorbent surface charge and the degree of anionic dye dissociation. This can be explained to the chemical form of dye in the solution and functional groups present on the adsorbent surface at a specific pH.