8 Sydnone-Based Cycloadditions in Click Chemistry

The 1,3-dipolar cycloaddition of sydnones (1,2,3-oxadiazolium-5-olates) with dipolarophiles, such as alkynes, has recently emerged as a versatile click reaction, with applications ranging from the mild and regioselective preparation of polysubstituted pyrazoles for drug discovery to the metal-free bioorthogonal ligation of biomacromolecules in living cells. This chapter reviews the importance of metal catalysis for controlling the regioselectivity of the copper-mediated reaction (CuSAC), as well as the development of fluorogenic probes, the click and release strategy, and photo-triggered ligations based on strain-promoted sydnone–alkyne cycloadditions (SPSAC).

Optimization of a Marine Fish Release Strategy: A Case Study of Black Sea Bream Acanthopagrus schlegelii in the Zhanjiang Estuary, Northern South China Sea

The release strategy (choice of the species and locations stocked, releasing mode, and stocking size and times) is an important part of quantitative evaluations of marine fish stock enhancement, while optimization of the release strategy can contribute to assess the stocking success intended to alleviate declining fishery resources and to increase the income of fishers. In this study, a typical fish species released in the northern South China Sea, black sea bream Acanthopagrus schlegelii, was taken as the research object. The biological characteristics of this sparid were determined from samples collected from waters in the Zhanjiang estuary during June, July, and September 2020 to April 2021, and the data were applied to estimate its length frequency and its growth parameters using the ELEFAN I run in FiSAT II. We then simulated and evaluated the stocking effects of five scenarios under different release strategies, while assuming a fixed total quantity of released fish and a constant of mortality rate at different life stages. The results showed that (1) the breeding season of black sea bream in this region is mainly from December to March of the next year, which is also the period when most significant sexual reversal in this species occurs, and (2) the relationship between standard length and weight in black sea bream is W = 5.092 × 10–5L2.906, L∞ = 54.39 cm, K = 0.15, and t0 = −0.967. (3) The recommended period to release black sea bream in Zhanjiang waters is from June to October. It appears more productive if the total quantity of fish released can be divided into two batches. The growth potential of released juvenile fish in this study was evaluated based on a density-dependent theory, and the stocking effect of released stocks was simulated with the consideration for biological parameters and field sampling technique. This study provides a reference for the optimization of fish release strategies in coastal waters.

Assessment of free-radical scavenging and anti-bacterial potential of Thymol conjugated with Gum Acacia-Chitosan copolymeric nanoformulation

This study details with thymol loaded on anionic copolymeric (Gum Acacia-Chitosan) nanoformulation prepared using ionic gelation to further enhance its therapeutic effectiveness. Optimized nanoparticles of 10:1 ratio (Gum Acacia:Chitosan) having entrapmentefficiency of 97% and mean hydrodynamic diameter of 172 nm (obtained using DLS) were characterized and in vitro examined for drug release effect, antioxidant potential and antibacterial activity. Zeta potential reading (-31.4 mV) confirmed optimized nanoformulation as stable and Electron-microscopy affirmed spherical morphology. FTIR analysis revealed entrapment as well as chemical-conjugation of thymol in polymer matrices. Thymol availability lasting more than 24 hours was verified in vitro by drug release experiments. Synthesized nanoformulation demonstrated superior antioxidant and antibacterial activity which may be attributable to its anionic charge, slow sustained release and synergistic effect provided by copolymers. Hence this investigation suggests control-release strategy using these copolymers for further utilization of thymol as natural therapeutic molecule by overcoming its solubility, stability and oxidation problems.

Existence and Uniqueness of Nontrivial Periodic Solutions to a Discrete Switching Model

To control the spread of mosquito-borne diseases, one goal of the World Mosquito Program’s Wolbachia release method is to replace wild vector mosquitoes with Wolbachia-infected ones, whose capability of transmitting diseases has been greatly reduced owing to the Wolbachia infection. In this paper, we propose a discrete switching model which characterizes a release strategy including an impulsive and periodic release, where Wolbachia-infected males are released with the release ratio α1 during the first N generations, and the release ratio is α2 from the (N+1)-th generation to the T-th generation. Sufficient conditions on the release ratios α1 and α2 are obtained to guarantee the existence and uniqueness of nontrivial periodic solutions to the discrete switching model. We aim to provide new methods to count the exact numbers of periodic solutions to discrete switching models.

Designing Educational Game to Increase Environmental Awareness

Plastic is a versatile material that is inexpensive and has the characteristics of being lightweight, strong, durable, anti-corrosive, with high thermal and electrical insulation properties. Regardless of the positive impact on economic development, it brings negative impacts on the environment. The amount of plastic waste, that continues to increase, pollutes the environment and ocean chronically. There needs to be a change in people behavior and awareness to reduce the use of it. In fact, raising awareness of the environment from the dangers of plastic waste is not an easy matter, but if taught since childhood, good environmental awareness and habits will be formed. This research tried to raise awareness among elementary school children in Indonesia of the dangers of plastic waste through an educational game developed using the Game Development Life Cycle (GDLC). GDLC consists of six phases: initiation, pre-production, production, testing, beta, and release. Strategy genre was chosen for engaging gameplay. Environmental awareness and knowledge on the danger of plastic waste were given integrally through storylines, gameplay, goals, and animated cutscenes. The results of testing at the beta stage on the respondents showed that 71.11% of primary school student respondents gained environmental knowledge.