Hydroxyl radical (HO·) formation initiated by the Fenton-type reactions of Fe and Cu complexes of l -leucine (Leu) amino acid as well as its oxidation reaction by HO· was computationally investigated by using the density functional theory method at the M05-2X/6-311++G(3df,2pd)//M05-2X/6-311++G(d,p) level of theory in the aqueous phase. The results showed that dipole-salt is the main form of Leu in the physiological condition. Leu exhibits high chelating potential towards both Fe(III)/Fe(II) and Cu(II)/Cu(I) ions with the most favourable coordinating positions at two oxygen atoms of the –COO functional group. Furthermore, the Leu-ions complexes show a high risk of HO· formation via Fenton-like reactions, especially when ascorbate anion exists in the environment as a reducing agent. Finally, the oxidation reaction of l -leucine by HO· demonstrated a relatively high overall apparent reaction rate, k overall , being 1.18 × 10 9 M −1 s −1 , in which formal hydrogen transfer reactions of the dipole-salt form occur as the primary mechanism. Consequently, the Leu oxidation by HO· radical can be promoted by the Fenton reaction enhancement of its transition metal complexes.

The main objective of this study was to assess the role of corporate social responsibility on tourism and hospitality in Vietnam. To accomplish this, we conducted a field survey and analysis on 886 tourism and hospitality in Vietnam over a 6-month period. The results show that corporate social responsibility helped businesses improve corporate reputation, increase customer satisfaction and improve financial performance of Vietnam tourism and hospitality. Customer satisfaction and corporate reputation had a statistically significant positive impact on the financial performance of these businesses. However, corporate reputation and customer satisfaction did not play a full mediate role in the relationship between corporate social responsibility and financial performance. Finally, we examined the moderate role of foreign ownership and size in the relationship between corporate social responsibility and financial performance, showing that both foreign ownership and firm size had a moderate role on the relationship between corporate social responsibility and financial performance. With the more percent of foreign owned, the implementation of corporate social responsibility, the stronger the impact on the financial performance, the less percentage of foreign owned, which means the implementation of corporate social responsibility had positive impact but less intense. The greater size of enterprises, the more corporate social responsibilities and the better financial performance. In contrast to the smaller businesses, the more corporate social responsibility, the worse financial performance. At the same time, we proposed several solutions to improve the corporate social responsibility for tourism and hospitality in Vietnam.

The oxidation of L-proline (Pro) by HO ● radical in water and the influence of transition metal ions on this process has been revisited by using the density functional theory (DFT) method at the M05-2X/6-311 + + G(3df,3pd)//M05-2X/6-311 + + G(d,p) level of theory at the temperature of 298.15 K. The main reactive sites of the HO ● –initiated oxidation of Pro via hydrogen atom transfer (HAT) reactions are at the β- and γ-carbon, with the branching ratios being 44.6% and 39.5%, respectively. The overall rate constant at 298.15 K is 6.04 × 10 8 M −1 s −1 . In addition, Pro tends to form stable complexes with both Fe and Cu ions via the –COO functional group of dipole-salt form. The most stable Cu(II)-Pro complexes have high oxidant risks in enhancing the HO ● formation in the presence of reducing agents. Besides this, the high oxidation state metal complexes, i.e. Fe(III)-Pro and Cu(II)-Pro, may be oxidized by HO ● radical via HAT reactions but with a lower rate constant than that of free-Pro. By contrast, the low oxidation state metal complexes (i.e. Fe(II)-Pro and Cu(I)-Pro) have higher oxidation risks than the free ligands, and thus, the complexation enhances the oxidation of Pro amino acid.

The activity concentrations of naturally occurring radionuclides 226Ra, 232Th, and 238U were determined in marine sediments, seawaters and seafood along the Gulf of Vietnam to establish baseline data for future environmental monitoring at a surface water depth of 0–3 cm. The concentration of uranium, thorium and radium were determined using a low background gamma spectrum as well as activity ofy of 238U(214Bi), 232Th(228Ac) and 226Ra. The mean radioactivity concentrations of 226Ra, 232Th, and 238U were found to be 8.59 ± 0.54, 1.31 ± 0.15, and 6.91 ± 0.64 Bq m−3, respectively, in seawater samples and 32.96 ± 1.90, 37.64 ± 1.91, and 39.28 ± 1.96 Bq kg−1, respectively, in marine sediments, 0.21 ± 0.03, 0.69 ± 0.11, and 0.19 ± 0.03 Bq kg−1, respectively, in fish samples and 0.23 ± 0.041, 0.41 ± 0.06, and 0.31 ± 0.06 Bq kg−1, respectively, in clam samples. The radioactivity concentrations in seawater are higher than those in sediment and compared with those reported in other countries. The mean values of distribution coefficient (L/kg) is 0.53, 0.13, and 0.23, respectively, in fish samples and 0.19, 0.16 and 0.13, respectively, in clam samples at Hai Phong, Quang Ninh and Ha Tinh. Moreover, the ecological dose at Hai Phong, Quang Ninh and Ha Tinh are 0.03, 0.02 and 0.02 µGy h−1, respectively, in fish and 0.02, 0.03, and 0.03 µGy h−1, respectively, in clams and the mean human’s seafood consumers dose rate is 1.13×10-6 Sv/yrs. Results were discussed and compared with those reported in similar studies and with internationally recommended values within limits recommended by UNSCEAR.

The Mong Cai area, coastal sediments were collected and analyzed for grain sizes, heavy metals, total organic carbon, and isotopes (210Pb, 226Ra, δ15N, δ13C) for assessing sediment quality.Which sediments common were fine sand in surface sediment, very fine sand in core C1, very coarse silt and coarse silt in core C2. The total organic carbon was highest in C2 next to the surface and lowest in C1, with content levels of 1.81%, 0.40%, and 0.31%, respectively. δ13C and δ15N in the sediment reflected the source of the organic matter mix from the marine and terrigenous sediments. Heavy metals were lower than ISQGs, exception of As in C1 and C2 were higher, in C1 showed a decline over time, while in C2 increased between 1996 and 2019. The Mong Cai area was common by sand, accumulation of heavy metals was small, impact of heavy metal pollution on ecosystems was low.