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An attempt to prepare a conductive hydrogel from recyclable and renewable resource as wastepaper was made. The suspension of a laboratory-made graphene oxide (GO) was introduced to the wastepaper paste. The preparation of hydrogel from the GO suspension/wastepaper mixture was performed in the presence of ammonium persulfate (APS) as the initiator, acrylic acid (AA) as the monomer, and N, N′-methylenebisacrylamide (MBA) as the crosslinking agent. The structural and morphological characterization of cellulose/GO hydrogel were carried out through Fourier-transform infrared spectroscopy and focused ion beam scanning electron microscopy. The properties of the material were characterized through the swelling degree, thermogravimetric analysis, differential scanning calorimetry, electrical conductivity, and mechanical properties. The effect of GO content on the properties of the materials was investigated. The results indicated that the hydrogel based on wastepaper and GO exhibited unique swelling, mechanical, thermal and electrical properties. The chemical linkage formed by GO and cellulose hydrogel may play an important role to improve properties of the hydrogel. It was found that the hydrogel achieved the outstanding properties when the GO content was 1.6 g/kg cellulose in the presence of 1.0 g APS/kg cellulose, 1.6 g AA/kg cellulose, and 0.2 g MBA/kg cellulose. In this condition, the thermal resistance of the obtained material was the best. The Young's modulus, tensile strength, elongation at break, Charpy impact of the obtained material was 7.3 MPa, 12.3 MPa, 411.1 5 and 10.2 kJ/m2, respectively. The best electrical conductivity was 0.013 S/cm. The material may be suitable for the application in flexible electronics field. [ABSTRACT FROM AUTHOR]

In this paper, an unmanned aerial vehicle (UAV) nonorthogonal multiple access (NOMA) system operating in millimeter-wave (mmWave) communications under the aid of multiple reconfigurable intelligent surfaces (RISs) is determined. Specifically, two NOMA users receive messages from UAV via both UAV-RISs-user and UAV-user links using mmWave communications. The closed-form expressions of outage probabilities (OPs) and achievable data rates (ADRs) are successfully derived over Nakagami-m fading channels to investigate the performance of the RISs aided UAV-NOMA-mmWave system. Computer simulations are provided to validate the derived expressions. Numerical results observe that by utilizing RISs, the OPs and ADRs performance of UAV-NOMA-mmWave system is significantly improved in comparison with the case without RISs. More specifically, even with high altitude of UAV (300 m) and high carrier frequency (50 GHz), the OPs of UAV-NOMA-mmWave system with RISs are remarkably lower than those without RISs. Meanwhile, the ADRs with RISs are only higher than those without RISs in low transmit power of UAV. In high transmit power of UAV, ADRs with and without RISs are similar due to the NOMA characteristics. Besides the distances and carrier frequency, the effects of other parameters such as the position of RISs, the number of reflecting elements (REs), and the altitude of UAVs are clarified to obtain the system behaviors. [ABSTRACT FROM AUTHOR]

In this work, we prepared successfully a recoverable heterogeneous magnetic nano-catalyst Fe3O4-MNPs@MMT-K10. This catalyst was characterized by energy-dispersive X-ray spectroscopy, vibrating sample magnetometry, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy techniques. Its catalytic behavior was efficiently used for the synthesis of highly substituted pyran/chromene derivatives (4a–m and 6a–m, respectively) containing propargyl unit through a one-pot three-component condensation of propargyl acetoacetate/3-propargyloxyphenol, malononitrile, and arylaldehydes under microwave-assisted solvent-free conditions. Some important features of this catalyst were found, including short reaction times, excellent yields, lower loading of the catalyst, easy work-up, and recyclability. It was showed that the obtained catalyst exhibited the catalytic stability and the reusability for a minimum of six times without any noticeable decrease in its catalytic activity. Also, thirteen novel substituted propargyl 6-amino-4-aryl-5-cyano-2-methyl-4H-pyran-3-carboxylates 4a–m were synthesized by three-component reaction of propargyl acetoacetate with malononitrile and benzaldehydes using this catalyst. Their structure was determined by measuring the spectral properties as well as by single-crystal X-ray crystallography of a representative compound 4i. 1-Alkyne was one of the two substances needed for click chemistry, along with organic azides and propargyl esters as well as ethers were synthesized for this purpose. [ABSTRACT FROM AUTHOR]

One of the most important advancements in harnessing the biological nitrification in the field is enrichment solution of nitrifying microbial consortia. In the current study, we developed an improved multi-step enrichment to amplify a targeted microbial consortium from a sediment sample collected in tropical mangrove, Vietnam. The results showed that it took 122 culturing days with five unique continuous enrichment steps, the microbial consortium consumed total 5665 mgN L−1. Relative substrate removal rate increased rapidly from 0.114 mgN L−1 h−1 at the end of the first-step enrichment up to 3.58 mgN L−1 h−1 at the end of the fifth-step enrichment. High-throughput sequencing revealed that Nitrospirae, Proteobacteria and Bacteroidetes were the dominant taxa at the phylum level while Nitrospira, Marinobacter, Denitromonas and Nitrosomonas were the dominant taxa at the genus level in the enriched consortia. A pilot-scale experiment for shrimp cultivation of L. vannamei in 84 day-period proved the efficiency of Total ammonium nitrogen and nitrite removal in the consortium-activated treatment was much higher than the control. [ABSTRACT FROM AUTHOR]

Motorcycles dominate current transport activities in Vietnamese cities; however, historical data show that bikes and public transport were popular as recently as 30 years ago. Because the transport infrastructure in Vietnamese cities makes it unsafe for cycling and inconvenient for public transport, many cyclists and public transport users switch to private motorized vehicles, particularly motorcycles, as soon as they can afford to make the change. The preference for motorcycles in Vietnamese cities has resulted in an increased risk of road traffic accidents and a degradation of air quality. Reducing the share of motorcycles on Vietnamese roads by improving public transport would be expected not only to improve public safety but also to have a positive impact on the environment and public health. However, efforts to improve the public transport have not yet been properly integrated into the local government system in every city. As the result, each city has different outcomes in mitigating the motorcycle-related challenges. This study examines travel behaviors in five major Vietnamese cities—Hanoi, Hai Phong, Da Nang, Ho Chi Minh City (HCMC), and Can Tho—and compares the impact of improved public transport on mode choice, emissions, and traffic safety. It is found that improving public transport would result in an 21.11 percent reduction in transport emissions by 2030 in Hanoi, as well as reductions of 12.5 percent in Hai Phong, 17.37 percent in Da Nang, 9.75 percent in HCMC, and 15.21 percent in Can Tho. The differences in these percentages are due to the heterogeneous modal shifts among cities. The provision of improved public transport is also shown to reduce the risk of road traffic accidents. The risk of a traffic fatality in Hanoi decreases by 49.6 percent, while in Hai Phong, the reduction is 43.8 percent; the risk in Can Tho, Da Nang and HCMC decreases by 18.7 percent, 19.8 percent, and 26.3 percent, respectively. As public transport investment is beginning to be adapted to the city context, our results indicate that investment capital on improving the public transport system would partly contribute on reducing emissions and traffic accidents in Vietnamese cities. [ABSTRACT FROM AUTHOR]

Pd(II) ions were introduced into Mg0.7Al0.3(OH)2(CO3)0.15·mH2O through the co-precipitation of the corresponding nitrate salts at a constant pH value. The presence of Pd in the brucite-like layers affects an increased surface area and decreased crystal domain of the Mg–Al hydrotalcite catalysts. Pd(II) ions may exist in both intra- and extra- brucite-like layers and exhibit different roles in the oxidation of styrene with t-BuOOH, depending on the amount of palladium. The insertion of Pd(II) into the hydrotalcite lattice has significantly improved the catalyst stability. The highest conversion of styrene is about 80% for the production of styrene oxide and benzaldehyde at low temperatures. [ABSTRACT FROM AUTHOR]

Pig farming systems in Vietnam are very diverse but little is known about this diversity. In particular, the different livestock farming systems currently in operation do not have the same capacity to be sustainable. The study aims to categorize farming systems involving pig production and investigate their sustainability. Data were collected from 160 family pig farms and 2 large-scale farms in Mai Son district of Son La province (northwest of Vietnam) using stratified random sampling. The multiple factor analysis method was used to identify different farms and to characterize each type with economic, social, and environmental indicators. The results highlighted four different farm types. Type 1 contained smallholder farms with diversified farm activities. They were mainly farmed by ethnic minorities located in the intermediate highland. They had low labor productivity and relied mainly on crop farming. Pig production was characterized by a low level of economic and social sustainability. Type 2 farms had comparatively less land and crops than other types. They were more specialized in livestock production, had medium-size pig herds, and were engaged in off-farm jobs. They were less dependent on credit or location and performed better with regard to environmental issues than larger farm types. Type 3 was specialized farms with large pig herds. They seemed more sustainable in economic and social components than the other types, but their environmental sustainability was questionable. Type 4 contained large mixed crop-livestock farms. They obtained high income but were more dependent on credit than the other types. In the future, in addition to focusing on large-scale specialized farms, policies should also consider small-scale and diversified farms because of their role in the sustainable development of national pig production. [ABSTRACT FROM AUTHOR]

In the recent past, pig performance and sow management on smallholder farms in the Southeast Asian Massif have been extensively researched. But the objective of this study was to investigate the lifetime efficiency of breeding sows of the local Vietnamese Ban ( n = 89) and Mong Cai ( n = 131) breeds in a production system context. The impact of sow longevity was considered in particular. In addition, predictors of early pre-weaning mortality in piglets were investigated. In total, nine villages of Son La province, situated in the uplands of north-western Vietnam, were selected, differing in access to markets, production intensity, and pig management level. Data was collected over a period of 10 years through an on-farm performance testing system. It was shown that sows of both breeds that achieved five or more parities farrowed and weaned significantly more piglets per life year compared to sows with only one or two parities. The conception rate (Spearman's rho = 0.374) and age at first farrowing (Spearman's rho = −0.424) were significantly correlated with the number of weaned piglets per life year of stayable (≥4 parities) Mong Cai sows. The risk of early pre-weaning death of piglets born to Mong Cai sows was affected more by litter size, while for piglets born to Ban sows, the risk was influenced more by the season. Therefore, interventions to improve the sow lifetime efficiency and piglet survivability must match the sow breed and management level. [ABSTRACT FROM AUTHOR]

Novel donor–acceptor (D-A) conjugated polymers containing phenothiazine and diketopyrrolopyrrole derivatives were successfully synthesized via direct arylation polymerization using the palladium catalyst system. The C-N coupling reaction was performed for the synthesis of 4-(10H-phenothiazin-10-yl)-N,N-diphenylaniline (PDA) and 10-(pyren-1-yl)-10H-phenothiazine (PYP) as donor monomers. The D-A conjugated polymers synthesized by polymerization of PDA/PY with diketopyrrolopyrrole have been characterized via GPC, 1H NMR, FTIR, XRD, DSC, PL and UV-Vis spectroscopy, and used for fabrication of organic field effect transistors. [ABSTRACT FROM AUTHOR]