Intrinsic limits governing MBE growth of Ga-assisted GaAs nanowires on Si(111)

Diffusion-enhanced and desorption-limited growth regimes of Ga-assisted GaAs nanowires were identified. In the latter regime, the number of vertical NWs with a narrow length distribution was increased by raising the growth temperature. The maximum axial growth rate; which can be quantified by the supplied rate of As atoms, is achieved when a dynamical equilibrium state is maintained in Ga droplets i.e. the number of impinging As atoms on the droplet surface is equivalent to that of direct deposited Ga atoms combining with the diffusing ones. The contribution of Ga diffusion to the wire growth was evidenced by the diameter-dependent NW axial growth rate

Vietnam’s Scientific Publications in the Period of COVID-19

The COVID-19 pandemic is considered a global disaster that affects all areas of the world; however, it is also seen as a motivation for domestic and foreign scientists to focus on researching solutions to reduce its damage. This article aims to explore the correlation of scientific publications of countries in Southeast Asia, among research fields in Vietnam and among topics published by Vietnamese educational institutions in the context of a pandemic. 1392 Southeast Asian countries’ publications related to COVID-19 were referenced from the Scopus database, including 123 articles from Vietnam (up to August 27th, 2020). Statistics show that Vietnam ranks fifth in the number of scientific publications with research cooperation of researchers from 20 different countries. Regarding the research fields of Vietnam, medicine is the main research topic, social science ranks third following environmental science. In the field of social science, articles focus on four key topics: epidemic prevention, reduction of pandemic effects on life and socioeconomics, factors related to online learning of students, healthcare for the elderly. From the analysis results, the authors recommend that researchers should pay attention to other topics in the social sciences that have not been published, such as psychological effects of infected or suspected nCovi, the impact of COVID-19 to disadvantaged groups in society..

Effects of Electroporation on Biological Membranes Exposed to High Potentials

This study first considers that voltages of cellular organelle membranes could significanly surpass these of plasma membranes under the influence of ultrashort and high-intensity electric pulse. This is due to the voltages induced on the membrane. Using an approximate theory coordinated with the Kotnik's analytical method, considering the electroporation, we focus on the reactions of cell membranes placed in a trapezoidal pulse. Then, we discuss conductive power dissipations of normal cell and cancer cell generated by a sinusoidal exposure which include dielectric relaxation effects. In comparison with  the complex numerical calculations of Joshi \textit{et al}, our results are in very good agreement

Residual strain and piezoelectric effects in passivated GaAs/AlGaAs core-shell nanowires

International audienceWe observe a systematic red shift of the band-edge of passivated GaAs/Al0.35Ga0.65As core-shell nanowires with increasing shell thickness up to 100 nm. The shift is detected both in emission and absorption experiments, reaching values up to 14 meV for the thickest shell nanowires. Part of this red shift is accounted for by the small tensile strain imposed to the GaAs core by the AlGaAs shell, in line with theoretical calculations. An additional contribution to this red shift arises from axial piezoelectric fields which develop inside the nanowire core due to Al fluctuations in the shell

Vertical transmission and early diagnosis of the microsporidian Enterocytozoon hepatonaei in Whiteleg Shrimp Penaeus vannamei

Microsporidia, which are ubiquitous obligate intracellular parasites responsible for a variety of diseases and economic losses in farming, have different transmission strategies. While horizontal transmission relies on sufûcient parasite numbers released into environment, vertical transmission requires host reproduction to occur leading to a lower virulence, and also induces a sex ratio distortion. The second strategy has been reported in a broad range of hosts from protists to mammals, in which insects and amphipod crustaceans as the most common. The present study shows the first evidence of vertical transmission of a microsporidia in decapod crustaceans via an experimental description of the infection by Enterocytozoon hepatopenaei (EHP) in whiteleg shrimp Penaeus vannamei. The group of healthy shrimp was infected with EHP by feeding with infected-shrimp tissue and sharing habitat. The presence of EHP in the infected shrimps was detected by using Polymerase Chain Reaction (PCR) method with specific primers EHP-510F/EHP-510R and histopathological analysis. The Nauplius, Zoae 1 and Zoae 2 stages collected from the infected female broodstocks demonstrated that EHP can infect offspring from their parental shrimp, and interestingly EHP can be detected from Nauplius stage of shrimp by the use of PCR method

A study on vegetative propagation of Huperzia serrata by cuttings in Sa Pa, Lao Cai

Huperzia serrata is a precious medicinal plant used in medicine to support and treat Alzheimer's disease. Currently, this species is in danger of extinction due to indiscriminate exploitation for commercial purposes. Furthermore, this species reproduces slowly and is difficult to cultivate artificially. The reproduction by spores of this species is very long and takes 15−20 years from the spore germination to mature plant, whereas asexual reproduction by tissue culture is also difficult. Therefore, cutting is an effective method to propagate this species on a large scale. In this study, we surveyed the factors affecting the survival rate, the rooting and the number of new leaves of the stem cuttings, including cutting length, growing substrate, and effects of growth-regulating hormones IBA (0 ppm, 500 ppm, 1000 ppm, 2000 ppm and 3000 ppm) and α-NAA (0 ppm, 10 ppm, 20 ppm, 30 ppm and 40 ppm). The experimental results showed that using cuttings of 6 cm in length treated with IBA at a concentration of 1000 ppm for 30 mins and cultured on the substrate mixture of soil, decomposed animal manure and rice husk at a ratio of 3:1:1 was the best for cuttings of H. serrata in Sa Pa. The results of this study will contribute to the conservation and development of genetic source of H. serrata in Vietnam.

Characterization of Ag-Doped p-Type SnO Thin Films Prepared by DC Magnetron Sputtering

Crystalline structure and optoelectrical properties of silver-doped tin monoxide thin films with different dopant concentrations prepared by DC magnetron sputtering are investigated. The X-ray diffraction patterns reveal that the tetragonal SnO phase exhibits preferred orientations along (101) and (110) planes. Our results indicate that replacing Sn2+ in the SnO lattice with Ag+ ions produces smaller-sized crystallites, which may lead to enhanced carrier scattering at grain boundaries. This causes a deterioration in the carrier mobility, even though the carrier concentration improves by two orders of magnitude due to doping. In addition, the Ag-doped SnO thin films show a p-type semiconductor behavior, with a direct optical gap and decreasing transmittance with increasing Ag dopant concentration

THÀNH PHẦN HÓA HỌC VÀ HOẠT TÍNH CHỐNG OXY HÓA CỦA CÁC DỊCH CHIẾT TỪ HOA XUYẾN CHI (Bidens pilosa)

Bidens pilosa is used in traditional medicine in Vietnam. The antioxidant potential of the ethanol extract and fractions from the flowers of Bidens pilosa was evaluated through DPPH and ABTS radical scavenging and the total antioxidant capacity method. The ethyl acetate fraction exhibits the highest activity with the lowest IC50 value (IC50 = 31.54 μg·mL–1 and IC50 = 35.33 μg·mL–1 for DPPH and ABTS radical scavenging capacity), and the total antioxidant capacity was 85.05 ± 0.28 mg GA·g–1. The composition of Bidens pilosa flowers: the total phenolic, total flavonoid, polysaccharides, and triterpenoid, was examined by using the colorimetric method, and their quantities are equivalent to 59.35 ± 0.83 mg GAE·g–1, 42.35 ± 1.50 mg QE·g–1, 4.44 ± 0.02%, and 32.88 ± 0.66 mg acid oleanolic·g–1, respectively. Specifically, the polysaccharide and total triterpenoid content of Bidens pilosa flowers was reported for the first time.Xuyến chi đã được sử dụng trong các bài thuốc cổ truyền Việt Nam. Khả năng chống oxy hóa của cao toàn phần và các cao phân đoạn từ hoa cây Xuyến chi được đánh giá thông qua ba mô hình: tổng khả năng chống oxy hoá, khả năng bắt gốc tự do DPPH và khả năng bắt gốc ABTS. Kết quả cho thấy cao ethyl acetate có khả năng chống oxy hóa tốt nhất với IC50 nhỏ nhất (IC50 = 31,54 μg·mL–1 và           IC50 = 35,33 μg·mL–1 tương ứng với khả năng bắt gốc DPPH và ABTS) và hàm lượng các chất chống oxy hóa cao nhất (85,05 ± 0,28 mg·g–1 acid gallic). Hàm lượng các hợp chất có hoạt tính sinh học (tổng các hợp chất phenol, tổng flavonoid, tổng triterpenoid và polysaccharide) trong dịch chiết hoa cây Xuyến chi được xác định bằng phương pháp trắc quang. Hàm lượng tổng các hợp chất phenol và flavonoid là 59,35 ± 0,83 mg GAE·g–1 và 42,35 ± 1,50 mg QE·g–1; hàm lượng polysacharide và triterpenoid là 4,44 ± 0,02% và 32,88 ± 0,66 mg acid oleanolic·g–1. Lần đầu tiên, tổng hàm lượng triterpenoid và polysacharide trong hoa Xuyến chi được công bố