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The present paper reported on the analysis of structural defects and their influence on the red‐emitting γ‐Al2O3:Mn4+,Mg2+ nanowires using positron annihilation spectroscopy (PAS). The nanowires were synthesized by hydrothermal method and low‐temperature post‐treatment using glucose as a reducing agent. X‐ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), and photoluminescence excitation (PLE) were utilized, respectively, for determining the structural phase, morphology and red‐emitting intensity in studied samples. Three PAS experiments, namely, positron annihilation lifetime (PAL), Doppler broadening (DB), and electron momentum distribution (EMD), were simultaneously performed to investigate the formations of structural defects in synthesized materials. Obtained results indicated that the doping concentration of 0.06% was optimal for the substitution of Mn4+ and Mg2+ to two Al3+ sites and the formation of oxygen vacancy (VO)‐rich vacancy clusters (2VAl + 3VO) and large voids (~0.7 nm) with less Al atoms. Those characteristics reduced the energy transfer between Mn4+ ions, thus consequently enhanced the PL and PLE intensities. Moreover, this optimal doping concentration also effectively controlled the size of nanopores (~2.18 nm); hence, it is expected to maintain the high thermal conductivity of γ‐Al2O3 nanowire‐phosphor. The present study, therefore, demonstrated a potential application of γ‐Al2O3 nanowire‐phosphor in fabricating the high‐performance optoelectronic devices. [ABSTRACT FROM AUTHOR]

Our study aimed to compare the essential oil (EO) concentration and composition of several Apiaceae species growing in the Northern region of Vietnam. The yields of EOs from materials ranged from 0.03% (root EO of Angelica acutiloba and aerial parts EO of Heracleum bivittatum)−0.27% (leaf EO of Xyloselinum vietnamense). Gas chromatography-mass spectrometry (GC-MS) allowed the identification of 74 components in the EOs of six Apiaceae species, making up 94.4%–100.0% of the oils. In EO from Angelica acutiloba , (Z)-ligustilide accounted for an extremely large proportion (94.9%). EO of Angelica pubescens was dominated by six characteristic components including α-pinene (21.5%), β-phellandrene (18.1%), p -cymene (12.2%), 3-methylnonane (8.7%), o -cymene (8.1%), and D-sylvestrene (6.2%). The EO from Cryptotaenia japonica was characterized by high amounts of α-selinene (48.7%), β-selinene (23.7%), and trans -β-farnesene (5.4%). The EOs from leaves and stems of Xyloselinum vietnamense were characterized by high concentrations of sabinene (69.8% and 33.8%), 4-terpineol (8.7% and 7.4%) and β-pinene (4.0% and 6.5%) while EOs from aerial parts and root of Xyloselinum leonidii comprise four characteristic monoterpenes including α-pinene (28.2% and 52.8%), β-pinene (7.9% and 10.3%), β-phellandrene (7.6% and 15.3%), and sabinene (3.0% and 4.1%). Additionally, cryptone is also one of the major components in the EO of Xyloselinum leonidii (13.2% in the aerial parts oil and 2. 8% in the root oil). In the EOs isolated from the aerial parts and root of Heracleum bivittatum , α-pinene (22.5% and 70.2%) and β-pinene (43.2% and 20.0%) were the predominant monoterpenes. Sabinene appeared in the EO from aerial parts of Heracleum bivittatum with a relatively high concentration (13.5%) while bornyl acetate (5.1%) was also one of the main components in the EO from its aerial parts but was not detected in other Apiaceae species in the present study. These databases help identify and control the quality of plant material studied from the family Apiaceae growing in Vietnam. [ABSTRACT FROM AUTHOR]

Essential oils isolated from leaves, twigs, fruit bark and seeds of Michelia tonkinensis collected in Muong Nhe Nature Reserve, Dien Bien province were obtained by hydrodistillation with yields of 1.5, 0.42, 0.16 and 4.6% respectively (v/w on dry weight basis). After analysis through GC, GC-MS and 13C NMR, 30, 34, 31 and 13 compounds (representing 96.4%, 96.8%, 97.1% and 99.9% of the whole composition, respectively) were identified in the leave, twig, fruit bark and seed essential oils. The main components were limonene (43.2%) and germacrene D (32.7%) in the leaf oil; limonene (67.1%) and germacrene D (10.4%) in the twig oil; limonene (66%) in the fruit bark oil; and safrole (90%) in the seed oil. Essential oils from the leaves and twigs showed strong inhibition against Staphyloccocus aureus. The fruit bark essential oil exhibited greater antibacterial potential against all 3 tested microorganisms (S. aureus, Escherichia coli and Candida albicans). The essential oil from seed displayed weak antibacterial activity against the three tested microorganisms. [ABSTRACT FROM AUTHOR]

Increasing active sites in catalysts is of utmost importance for catalytic processes. In this regime, single‐atom dispersing on graphitic carbon nitrides (g‐C3N4) to produce fine chemicals, such as hydrogen peroxide (H2O2), is of current interest due to not only enhancing catalytic performance but also reducing the loading of necessary metals. Herein, g‐C3N4 is engineered by atomically dispersing aluminum (Al) or indium (In) sites to provide catalytic active centers via one‐step thermal shock polymerization. The addition of Al and In sites can accelerate the catalytic efficacy owing to the Lewis acid–base interactions between these metals and oxygen (O2). Under catalytic conditions, the formation of oxygenic radicals will strongly be associated with the enhanced formation of H2O2, confirmed by in situ electron paramagnetic resonance spectroscopy. Furthermore, the empirical analyses from positron annihilation spectroscopy show that In atoms will occupy the near positions of carbon vacancies (VC) to form NVC@InO bonds. This replacement will produce the highest formation energy based on the density functional theory calculations, improving the stability of atom‐dispersive materials. Therefore, via the combination of experimental and theoretical proofs, this study suggests the exact location of In atoms in g‐C3N4 structures, which can help boost the catalytic production of H2O2. [ABSTRACT FROM AUTHOR]

Elucidating the impact of heteroatoms in graphitic carbon nitrides (g‐C3N4) is of utmost importance to rationalize materials. Hence, in this study, oxygen‐doped g‐C3N4 containing trace amounts of halogen in the structures for piezo‐photosynthesis of hydrogen peroxides (H2O2) is fabricated. The findings reveal that oxygen atoms may be inserted into g‐C3N4 in‐plane structures, while halogen atoms tend to become intercalated between g‐C3N4 layers. Furthermore, the presence of ammonium molten salts (NH4X) during the synthesis alters the concentration of mono and cluster vacancies of carbon and nitrogen in the materials, certifying by positron annihilation spectroscopy (PAS). These defective contributions will be meaningfully accelerate catalytic performance by providing trapping states. Additionally, the decomposition of generated H2O2 can produce highly oxidative hydroxyl radicals, inducing degradations on the catalyst's structures and unexpectedly decreasing catalytic outcomes. From the mechanistic view, different reduction and oxidation channels will be play a pivotal role in generating H2O2. Moreover, the influence of ultrasound and light is also carefully investigated in the work to gain more insights into how the catalysts are triggered to improve catalytic performance. Thus, this study highlights the importance of carefully characterizing structures of g‐C3N4 to precisely understand the catalytic properties, benefiting catalytic design and development. [ABSTRACT FROM AUTHOR]

Keteleeria davidiana (C.E.Bertrand) Beissn. is a species of conifer native to southern China, Laos and Vietnam. The species has been listed as vulnerable in Vietnam. Essential oil samples have been isolated from leaves, twigs and wood, and their compositions investigated for the first time by combination of chromatographic and spectroscopic techniques [GC-FID, GC-MS and13C NMR]. The composition of leaf essential oil was dominated by α-pinene (28.1%), β-pinene (15.8%) and (E)-β-caryophyllene (13.8%). Twig essential oil contained mainly α-pinene (37.9%) and β-pinene (24.7%) accompanied by (E)-β-caryophyllene (8.3%) and β-phellandrene (7.5%). Lastly, α-pinene (27.9%), α-terpineol (20.3%) and (E)-β-caryophyllene (20.8%) were predominant in wood essential oil. [ABSTRACT FROM AUTHOR]

The chemical composition and anti-inflammatory activity of the endemic Lysimachia baviensis were investigated for the first time in this study. A phytochemical fractionation of the methanol extract of L. baviensis resulted in the isolation of a new stilbene (bavienside A, 1) and two new chalcone glycosides (baviensides B and C, 2 and 3). Their structures were elucidated via the interpretation of NMR and HRESIMS spectroscopic data. Compounds 1–3 strongly inhibited the production of nitric oxide in LPS-induced RAW264.7 cells with the IC50 values of 6.23, 2.86 and 3.51 μM, respectively. The C-acetylstilbene and carbomethyl chalcone structures in compound 1 and 3 were found for the first time from natural source and could be important markers for chemotaxonomy of Lysimachia baviensis. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the result of gamma knife radiosurgery (GKRS) for drug-resistant primary trigeminal neuralgia (TN). Methods: Patients who were diagnosed with drug-resistant primary TN were treated with GKRS at the Nuclear Medicine and Oncology Center, Bach Mai Hospital from January 2015 to June 2020. Using the pain rating scale of the Barrow Neurological Institute (BNI), follow-ups and evaluations were conducted at 1 month, 3 months, 6 months, and 9 month, and 1, 2 years, 3 years, and 5 years after radiosurgery. Comparisons of pain levels was performed before and after radiosurgery according to the BNI scale. Results: From January 2015 to June 2020, 33 patients were treated with GKS. There were 23 female patients and 10 male patients; the average age was 61.9. The average onset time of disease was 4.42 years. Among all patients, 84.8% of patients were relieved from pain and 78.8% were pain-free without medication. The mean time for pain relief was 3 months and was not related to the dose of GKS (<80 Gy and >80 Gy). The efficacy of pain relief is not related to blood vessel contact with the trigeminal nerve, the dose of GKS, and the onset of disease. The rate of recurrence after the first pain relief was low (14.3%). Conclusions: Gamma knife is an effective method for the treatment of primary drug-resistant TN, especially in elderly patients with underlying medical conditions. The analgesic effect does not depend on the presence of nerve-vascular conflict. [ABSTRACT FROM AUTHOR]

This paper presents the results of the first observation of airborne trace elements using Barbula Indica moss in Hai Phong city, one of the two largest seaport cities in Vietnam. A total of 39 moss samples were collected at 39 different locations in January 2020 in Hai Phong. Neutron activation analysis method was used to analyze the concentration of 36 chemical elements in the collected moss samples and the obtained data were compared with the data obtained in other regions of Vietnam, China and Europe. The level of chemical elemental contamination in the air of Hai Phong was categorized and the possible sources of pollutant emissions were identified by applying principal component analysis. [ABSTRACT FROM AUTHOR]

The empirical heat capacities of some hot-rotating A ∼ 200 nuclei (184Re, 200Tl, 211Po, and 212At) have been investigated by combining the angular-momentum dependent back-shifted Fermi gas (BSFG) model of nuclear level density (NLD) with the experimental NLD data extracted from the neutron-evaporation spectra at the average total angular momentum ⟨ J ⟩ = 12 ℏ. The parameters of the BSFG are obtained by fitting its NLD to the corresponding measured data using an advanced package of program modeling (CPM) provided by Python feature of IBM decision optimization CPLEX. The results obtained show that the shell correction plays an important role in the formation of empirical S -shaped heat capacity, which serves as a fingerprint for the pairing phase transition in finite nuclear systems. The 184Re nucleus, which is deformed and has small shell correction, exhibits a weaker S -shaped heat capacity than the remaining three spherical 200Tl, 211Po, and 212At nuclei that have large shell effects. This result contrasts with that recently predicted by the microscopic exact pairing plus independent-particle model at finite temperature (EP + IPM), in which the S -shaped heat capacity was predicted in 184Re only. This discrepancy between the heat capacities obtained within the BSFG and EP + IPM models suggests that an NLD model capable of well describing the experimental data while also having intrinsic and as complete as possible physical interpretations is still required in order to provide the exact description of nuclear thermodynamic quantities. In addition, more experimental NLD data in other mass and higher energy regions are also demanded. [ABSTRACT FROM AUTHOR]

The morphology and elemental compositions at the surface of poly(styrene sulfonic acid) (PSSA) grafted poly(ethylene‐co‐tetrafluoroethylene) polymer electrolyte membranes (ETFE‐PEMs) in a grafting degree (GD) range of 0%–127% are investigated by using FE‐SEM and XPS analyses. The concentrations of elemental components at the surface are not a linear function of GDs, resulting from different grafting speeds at the surface and bulk. In addition, low accumulation of PSSA grafts on the surface of ETFE‐PEMs in the low GDs of 0%–19%, as well as their homogeneous distribution through the membranes at least at a GD of 19% are observed. At higher GDs of 19%–127%, the PSSA accumulation on the surface is relatively limited, indicating the presence of more PSSA grafts inside the bulk than on the surface. The surface signatures of ETFE‐PEMs over the entire GD range can be determined based on the grafting process. These interesting observations suggest the significant advantages of interfacial properties of ETFE‐PEMs for fuel cell applications. [ABSTRACT FROM AUTHOR]

The present work investigates the primary adsorption mechanisms of lead (II) and cadmium (II) cations onto pomelo fruit peel (PFP) from aqueous solution. pH, adsorption time, ion strength, and initial metal cation concentrations, which are factors affecting the uptake of these cations, are investigated. Results show that pH and ion strengths strongly affect the removal of these cations from aqueous solution. Different isotherm adsorption models, such as Langmuir, Freundlich, and Sips, are utilized to fit the experimental data in order to determine the adsorption in nature. The Langmuir monolayer adsorption capacities are found to be 47.18 mg/g for lead (II) and 13.35 mg/g for cadmium (II). Kinetic and thermodynamic studies based on a combination of FT-IR and TG-DSC spectroscopies demonstrate that electrostatic attraction plays a primary adsorption mechanism of lead (II) and cadmium (II) cations onto pomelo fruit peel. [ABSTRACT FROM AUTHOR]

A normalization procedure has been applied to improve the descriptive and predictive power of the enhanced generalized superfluid (EGS) model for the nuclear level density (NLD). In this procedure, the EGS model is normalized based on the experimental average level spacing at the neutron binding energy D 0 and the cumulative number of experimental discrete levels in the low-energy region N(E). The values of normalization parameters are determined by systematically analyzing a set of 288 nuclei from 25 Mg to 251 Cf, whose experimental D 0 and N(E) data are available. The systematical analysis permits to determine the values of the normalization parameters for any nucleus. The descriptive and predictive power of the normalized EGS (NEGS) model are demonstrated by making the comparison of the NEGS NLDs with the experimental NLD data of 70 nuclei obtained from the Oslo method. The results obtained show that the NEGS model describes reasonably well almost all the experimental NLDs and should be better used in the reaction codes than the conventional EGS, in particular for nuclei whose experimental NLDs are not available. [ABSTRACT FROM AUTHOR]

This article presents a composite (COM) method to obtain the high-resolution pulse shape discrimination (PSD) for the neutron and gamma-ray pulses generated from scintillation detectors. The method, which is based on a selective combination of the digital charge integration (DCI) with the reference pulse method, aims to reduce the mixed radiation events in the low-energy range. An EJ-301 liquid scintillation detector together with a fast sampling analog-to-digital converter (ADC) is used to measure and digitize the pulses induced from the radioactive decays of 60Co and 252Cf, which are then analyzed by our COM method. The proposed method is evaluated using the figure of merit (FoM) and separation quality function $F(u)$ , and the results are compared with three known methods, namely the DCI, standard event fit (SEF), and artificial neural network (ANN) methods. We show that the average values of FoM and $F(u)$ obtained within the COM method are about ten times higher than those obtained within the DCI and SEF in the whole energy range from 50 to 1000 keV electron equivalent (keVee). In particular, by using the COM method, the percentage of gamma events being confused as neutrons ranges from 0.32% to 8.80% when the energy is reduced from 400 to 50 keVee. This finding, which is significantly lower than those obtained by using the DCI and SEF, indicates that the proposed COM method should be considered as a leading method for producing a neutron/gamma PSD counter system with high resolution. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically investigate 21 projectile-target combinations of stable isotopes for the pre-synthesis parameters and production cross sections of the unknown superheavy 309,312126 nuclei. It is found that 61Ni + 248Cf and 64Ni + 248Cf combinations are the best candidates for the synthesis of the 309,312126 isotopes due to their largest cross sections of 0.03 and 3.6 pb, respectively. Besides, the results in the present and previous works indicate that the uncertainty, from pb to zb, in the synthesis cross sections of superheavy nuclei should be narrowed for a decision of measurements using the presently available facilities. This study, thus, provides valuable data for the synthesis of 126th element. [ABSTRACT FROM AUTHOR]

Biotic and abiotic factors control aboveground biomass (AGB) and the structure of forest ecosystems. This study analyses the variation of AGB and stand structure of evergreen broadleaved forests among six ecoregions of Vietnam. A data set of 173 1-ha plots from 52 locations in undisturbed old-growth forests was developed. The results indicate that basal area and AGB are closely correlated with annual precipitation, but not with annual temperature, evaporation or hours of sunshine. Basal area and AGB are positively correlated with trees > 30 cm DBH. Most areas surveyed (52.6%) in these old-growth forests had AGB of 100–200 Mg ha−1; 5.2% had AGB of 400–500 Mg ha−1, and 0.6% had AGB of > 800 Mg ha−1. Seventy percent of the areas surveyed had stand densities of 300–600 ind. ha−1, and 64% had basal areas of 20–40 m2 ha−1. Precipitation is an important factor influencing the AGB of old-growth, evergreen broadleaved forests in Vietnam. Disturbances causing the loss of large-diameter trees (e.g., > 100 cm DBH) affects AGB but may not seriously affect stand density. [ABSTRACT FROM AUTHOR]

The changes of the lamellar periods (L1D), thickness of lamellar crystals (Lc), and amorphous layers (La) within the stacked lamellae of poly(styrenesulfonic acid)‐grafted poly(ethylene‐co‐tetrafluoroethylene) polymer electrolyte membranes (ETFE‐PEMs), induced by the preparation and water‐absorbing steps are investigated using the small‐angle X‐ray scattering method. The L1D values of all the samples quickly increase at a grafting degree (GD) range of less than 19% and then level off. The solvent‐induced recrystallization is observed at the early stage of grafting (GD < 10%) and at successive sulfonation and hydration steps. The L1D, La, and Lc of dry and hydrated PEMs show similar values at higher GD ranges (>34%), leading to the conclusion that most water molecules in the PEMs with higher GDs exist at the outside of the lamellar stacks. Accordingly, for the PEMs with low GD (<19%), all the hydrophilic graft‐polymers (ion‐channels) locate in the lamellar stacks and are strongly restricted by lamellar crystalline layers, which suppress the swelling of the PEMs. The unique lamellar structures of ETFE‐PEMs characterized by La and Lc are well connected with the high conductance and mechanical properties of the membranes, and are suitable for fuel cell applications. [ABSTRACT FROM AUTHOR]

The sequencing batch reactor (SBR) has been increasingly applied in the control of high organic wastewater. In this study, SBR with aerobic granular sludge was used for wastewater treatment in a noodle-manufacturing village in Vietnam. The results showed that after two months of operation, the chemical oxygen demand, total nitrogen and total phosphorous removal efficiency of aerobic granular SBR reached 92%, 83% and 75%, respectively. Bacterial diversity and bacterial community in wastewater treatment were examined using Illumina Miseq sequencing to amplify the V3-V4 regions of the 16S rRNA gene. A high diversity of bacteria was observed in the activated sludge, with more than 400 bacterial genera and 700 species. The predominant genus was Lactococcus (21.35%) mainly containing Lactococcus chungangensis species. Predicted functional analysis showed a high representation of genes involved in membrane transport (12.217%), amino acid metabolism (10.067%), and carbohydrate metabolism (9.597%). Genes responsible for starch and sucrose metabolism accounted for 0.57% of the total reads and the composition of starch hydrolytic enzymes including α-amylase, starch phosphorylase, glucoamylase, pullulanase, α-galactosidase, β-galactosidase, α-glucosidase, β-glucosidase, and 1,4-α-glucan branching enzyme. The presence of these enzymes in the SBR system may improve the removal of starch pollutants in wastewater. [ABSTRACT FROM AUTHOR]

A new species, Asarum yentuense N. Tuan & Sasamoto (Aristolochiaceae), is described from Quang Ninh Province, Vietnam. This species belongs to A. subgen. Heterotropa sect. Longistylis and is most similar to Asarum petelotii, A. glabrum, A. reticulatum and A. magnificum var. dinghuense, but is differentiated by morphology, including the length of the calyx tube and lobes, and phenology. [ABSTRACT FROM AUTHOR]

Background: To determine the relationship between Helicobacter pylori (H. pylori) infection and the precancerous gastric lesions: atrophic gastritis (AG) and intestinal metaplasia (IM) and dysplasia. Methods: A total of 347 dyspeptic patients, including 141 H. pylori-positive patients and 206 H. pylori-negative patients, were studied alongside age- and sex-matched controls. The patients underwent gastroscopy and endoscopic biopsy for detection of H. pylori, and histological examinations. Helicobacter pylori was detected by a urease test (CLO; Delta West; Bentley, Australia), by histology (H&E stain, Giemsa) and by serology (BioSig; BioMeditech, NJ, USA). Atrophic gastritis, IM and dysplasia were detected by histological examination (Giemsa, H&E stain). Results: There is a higher rate of atrophic gastritis in H. pylori-positive than in H. pylori-negative patients (46 vs 13.5%, odds ratio (OR) = 5.4; P < 0.01). Gastritis in H. pylori-positive patients also has a higher rate of activity than in H. pylori-negative patients. The rate of IM is higher in H. pylori-positive patients than in H. pylori-negative patients (35 vs 11%; OR = 4.3; P < 0.01). Metaplasia is more often diffuse in H. pylori-positive than in H. pylori-negative patients. Dysplasia is more common in H. pylori-positive than in H. pylori-negative patients (12 and 3.8%; OR = 3.3; P < 0.01). Conclusions: This study supports the suggestion of a relationship between H. pylori infection and precancerous gastric lesions. Wherever H. pylori is present, the precancerous lesions are more common and more severe. [ABSTRACT FROM AUTHOR]