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Abstract In this work, we present the results of the ortho-positronium (o-Ps) annihilation lifetimes and nitrogen adsorption measurements for different porous materials and an approach for describing the annihilation of o-Ps in a pore, which results in a surface-volume formula (SVF) for calculating the pore-related o-Ps lifetime. This proposed formula gives the relationship between the o-Ps annihilation rate and the effective pore radius, bulk composition, and pore structure, including pore geometry and topology. The pore-related o-Ps lifetimes of different materials calculated by the SVF are consistent with experimental results for both micro- and mesopores (and macropores) with different geometries and topologies. The SVF is convenient for calculations of pore dimensions for many cases of metal organic frameworks and zeolites. This approach enables us to fully explain the temperature dependence of the o-Ps annihilation lifetime over a wide temperature range, 20–700 K.

Salmonella enterica is one of dangerous food-borne pathogens listed by the World Health Organization (WHO). In Vietnam, poultry is one of the most widely eaten meats and is reported as a common source of S. enterica contamination. The aim of this study was to examine multi-resistant Salmonella strains, to identify susceptibility to antibiotics by using 15 different types of medications and to perform sequencing to analyze antibiotic resistance genes, genotypes, multi-locus sequence-based typing (MLST), and plasmids. The result of the antibiotic susceptibility test indicated that phenotypic resistance to 9–11 types of antimicrobials was confirmed in all strains. Among 06 sequenced strains, we identified 43 genes associated with antibiotic resistance: strains carrying a range of genes that are associated with aminoglycoside resistance (aac(3), aac(6), ant(3), aph(3), aph(6), aadA); all strains carried blaCTX-M-55 or blaCTX-M-65 gene, which were resistant to the 3rd generation antibiotics; there were also frequently observed sul1, sul2, sul3, tet (A), qnrS1, floR, dfrA14 or dfrA27 genes in sequenced isolates. Besides, the genome sequencing also indicated that all strains carried pathogenicity islands SPI 1, SPI 2, and SPI 3 thereby creating many potential triggers of the disease. Additionally, some carried C63PI, SPI 9, SPI 13, SPI 14, and plus some plasmids such as Col156, IncHI2, IncHI2A, IncFIB, Col (MGD2).

Rhodotorula is a genus of marine yeasts that is considered the most suitable for carotenoid production. In this study, collected soils at Kien Giang and Tra Vinh provinces were cultured on yeast extract peptone dextrose (YEPD) agar for 72 hours at room temperature. Twenty-three isolates exhibiting yellow, orange, and pink pigments were tested for physiological and biochemical characteristics such as carbohydrate fermentation and assimilation, nitrate assimilation, urease production, and growth temperature. Their oval dimensions were 4.24x3.64 μm for isolate 5S1-T and 3.88x3.17 μm for isolate 5S4-T. The two isolates could assimilate carbohydrate and nitrate sources and produce urease. The ITS rDNA sequence of isolates 5S1-T and 5S4-T both had 100% matches to Rhodotorula sphaerocarpa CBS:5940 and Rhodotorula sphaerocarpa CBS:5939, respectively. The maximum absorbance wavelengths of the solution extractions from the 5S1-T and 5S4-T were 496 and 487 nm, respectively. The total carotenoid content of strain 5S1-T was found to be the highest (1.81 mg/l) followed by strain 5S4-T (1.16 mg/ml). The antioxidant abilities of the 5S1-T and 5S4-T were demonstrated by scavenging the free radical DPPH and ferric reducing capacity. The free radical scavenging activity of the extract from isolate 5S1-T (96.15%) was higher than that of isolate 5S4-T (88.61%) at 0.14 mg/ml. The absorbance at 700 nm of the extracts of both 5S1-T and 5S4-T significantly increased from 0.05 to 0.3 mg/ml. The two strains 5S1-T and 5S4-T of Rhodotorula sphaerocarpa discovered in this study could contribute to carotenoid and antioxidant-producing yeasts for industries in the future.

Abstract Background Vietnam possesses a vast diversity of rice landraces due to its geographical situation, latitudinal range, and a variety of ecosystems. This genetic diversity constitutes a highly valuable resource at a time when the highest rice production areas in the low-lying Mekong and Red River Deltas are enduring increasing threats from climate changes, particularly in rainfall and temperature patterns. Results We analysed 672 Vietnamese rice genomes, 616 newly sequenced, that encompass the range of rice varieties grown in the diverse ecosystems found throughout Vietnam. We described four Japonica and five Indica subpopulations within Vietnam likely adapted to the region of origin. We compared the population structure and genetic diversity of these Vietnamese rice genomes to the 3000 genomes of Asian cultivated rice. The named Indica-5 (I5) subpopulation was expanded in Vietnam and contained lowland Indica accessions, which had very low shared ancestry with accessions from any other subpopulation and were previously overlooked as admixtures. We scored phenotypic measurements for nineteen traits and identified 453 unique genotype-phenotype significant associations comprising twenty-one QTLs (quantitative trait loci). The strongest associations were observed for grain size traits, while weaker associations were observed for a range of characteristics, including panicle length, heading date and leaf width. Conclusions We showed how the rice diversity within Vietnam relates to the wider Asian rice diversity by using a number of approaches to provide a clear picture of the novel diversity present within Vietnam, mainly around the Indica-5 subpopulation. Our results highlight differences in genome composition and trait associations among traditional Vietnamese rice accessions, which are likely the product of adaption to multiple environmental conditions and regional preferences in a very diverse country. Our results highlighted traits and their associated genomic regions that are a potential source of novel loci and alleles to breed a new generation of low input sustainable and climate resilient rice.

In the field of robotics, especially in exoskeleton‐based rehabilitation robots, motion planning is an important problem. An effective motion trajectory must ensure naturalness and similarity to daily human movements. In this study, the researchers proposed using the dynamic movement primitives (DMPs) method to create trajectories similar to the actual trajectories of daily human activities. Subsequently, the study proposed and constructed a recurrent neural network (RNN) model to solve the inverse kinematics (IK) problem. This model was trained using a large dataset generated from the DMP algorithm mentioned earlier. The IK results applied to simulations on the upper limb exoskeleton robot of Vietnam (UExosVN) under development showed that the obtained trajectories have high accuracy and stability, suitable for control and similar in form to the desired trajectories. The study conducted experiments with two activities of daily living (ADL), namely the playing ball task and drinking water task. The errors in joint variables for the IK problem are all under 1°, except for joint five, which does not significantly impact the robot's end‐point accuracy. The shape similarity level in the predicted trajectory compared to the test data is mostly above 0.75. The combined approach of DMP and RNN provides a potential solution for designing motion trajectories for rehabilitation robots. [ABSTRACT FROM AUTHOR]

Contamination of antibiotic-resistant bacterial pathogens in raw food is becoming an increased health risk in numerous countries, including Vietnam where raw herbs and vegetables are used daily in many dishes as a flavor enhancer and a source of vitamin and nutrients. However, raw vegetables can also be a reservoir of various foodborne pathogens such as Pseudomonas spp. and Enterobacteriaceae. In this study, we evaluated the extent of Pseudomonas spp. contamination in 180 ready-to-eat (RTE) vegetables samples from restaurants in Hanoi, examined their antibiotic susceptibility profiles and determined the ability to produce β-lactamase enzymes of Pseudomonas spp. strains. Our results showed that 21.67 % (n = 39) of ready-to-eat vegetables samples in Hanoi were contaminated with Pseudomonas spp.. Of those, sixteen samples were determined to be β-lactamase producing strains including Pseudomonas putida, P. mendocina and P. aeruginosa. Further analysis revealed six strains (37.50 %) producing extended spectrum β-lactamase (ESBL) enzyme, five strains (31.25 %) producing ampC β-lactamase enzyme and five strain (31.25 %) producing both ESBL and ampC β-lactamases. It can be concluded that ready-to-eat vegetables in Hanoi would be a source of contamination of β-lactamase producing Pseudomonas spp. that could pose a threat to public health in the community.

A long-term issue that has hampered the efficient operation of heavy-haul tracks is the migration of fluidized fines from the shallow soft subgrade to the overlying ballast, i.e., mud pumping. This paper presents a series of undrained cyclic triaxial tests where realistic cyclic loading conditions were simulated at low confining pressure that is typical of shallow subgrade beneath a ballast track. Subgrade soil specimens with a low-plasticity index collected from a field site with recent history of mud pumping were tested at frequencies from 1.0 to 5.0 Hz and a cyclic stress ratio (CSR) from 0.1 to 1.0. The experimental results indicate that under adverse loading conditions of critical cyclic stress ratio ([CSR.sub.c]) and frequency, there is upward migration of moisture and the finest particles towards the specimen top and this causes the uppermost part of the soil specimen to soften and fluidize. Conversely, a smaller value of CSR tends to maintain stability of the specimen despite the increasing number of loading cycles. It is noteworthy that for any given combination of CSR and frequency, the relative compaction has a significant influence on the cyclic behaviour of the soil and its potential for fluidization. Key words: fluidization, cyclic triaxial test, mud pumping, subgrade. Sur le long terme, un probleme qui empeche l'exploitation efficace des voies de transport lourd est celui de la migration des fines fluidifiees de la plate-forme molle peu profonde vers le ballast sus-jacent, c'est-a-dire le pompage de la boue. L'article presente une serie d'essais triaxiaux cycliques non draines, qui ont permis de simuler des conditions de chargement cycliques realistes a une faible pression de confinement, typique d'une plate-forme peu profonde sous une voie de ballast. On a teste des echantillons de sol de fondation a faible indice de plasticite, preleves sur un site de terrain ayant des antecedents recents de pompage de boue, a des frequences de 1,0 a 5,0 Hz et un rapport de contrainte cyclique (CSR) de 0,1 a 1,0. Dans des circonstances de charge defavorables, les resultats experimentaux indiquent que dans des conditions de rapport de contrainte cyclique (CSRJ et de frequence critiques, on observe une migration vers le haut de l'humidite et des particules les plus fines vers le sommet de l'echantillon, ce qui entraine un ramollissement et une fluidification de la partie superieure de l'echantillon de sol. En revanche, une valeur plus faible du CSR a tendance a maintenir la stabilite de l'echantillon malgre le nombre croissant de cycles de chargement. Il faut remarquer que pour chaque combinaison donnee de CSR et de frequence, la compaction relative a une importante influence dans le comportement cyclique du sol et son potentiel de fluidification. [Traduit par la Redaction] Mots-cles : fluidisation, essai triaxial cyclique, pompage de boue, plate-forme., 1. Introduction The rapidly increasing demand for faster and heavier passenger and freight transport (Schut and Wisniewski 2015; Correia et al. 2016; ARTC 2018) has led to the inevitable need [...]