The influence of lithology and tectonics on the development of the karst landscape in the Dong Van Global Geopark, NE Vietnam

The Dong Van Karst Plateau Geopark is located in the mountainous area of the northern part of Vietnam. It became the 77th member of the Global Geoparks Network in 2010. The Dong Van Karst Plateau Geopark is a unique combination of breathtaking scenery and culture of ethnic groups, with many potential values such as its geoheritage, biological diversity and historical places, which attract many domestic and foreign visitors. Up to 60% of the area of this geopark is covered by karst. Its topography is strongly dissected by deep river gorges with steep slopes, and this area has experienced several deformational phases from the Middle Cambrian/Early Ordovician, to the Cenozoic. These elements contributed to the breathtaking scenery of the Dong Van Karst Plateau Geopark, the first global geopark in Vietnam and the second in South-East Asia

Visualizing thickness-dependent magnetic textures in few-layer Cr2Ge2Te6\text{Cr}_2\text{Ge}_2\text{Te}_6

Magnetic ordering in two-dimensional (2D) materials has recently emerged as a promising platform for data storage, computing, and sensing. To advance these developments, it is vital to gain a detailed understanding of how the magnetic order evolves on the nanometer-scale as a function of the number of atomic layers and applied magnetic field. Here, we image few-layer $\text{Cr}_2\text{Ge}_2\text{Te}_6$ using a combined scanning superconducting quantum interference device and atomic force microscopy probe. Maps of the material's stray magnetic field as a function of applied magnetic field reveal its magnetization per layer as well as the thickness-dependent magnetic texture. Using a micromagnetic model, we correlate measured stray-field patterns with the underlying magnetization configurations, including labyrinth domains and skyrmionic bubbles. Comparison between real-space images and simulations demonstrates that the layer dependence of the material's magnetic texture is a result of the thickness-dependent balance between crystalline and shape anisotropy. These findings represent an important step towards 2D spintronic devices with engineered spin configurations and controlled dependence on external magnetic fields.Comment: 15 pages, 4 figures, and supplementary informatio

Room-temperature ferromagnetism in monolayer WSe2 semiconductor via vanadium dopant

Diluted magnetic semiconductors including Mn-doped GaAs are attractive for gate-controlled spintronics but Curie transition at room temperature with long-range ferromagnetic order is still debatable to date. Here, we report the room-temperature ferromagnetic domains with long-range order in semiconducting V-doped WSe2 monolayer synthesized by chemical vapor deposition. Ferromagnetic order is manifested using magnetic force microscopy up to 360K, while retaining high on/off current ratio of ~105 at 0.1% V-doping concentration. The V-substitution to W sites keep a V-V separation distance of 5 nm without V-V aggregation, scrutinized by high-resolution scanning transmission-electron microscopy, which implies the possibility of the Ruderman-Kittel-Kasuya-Yoshida interaction (or Zener model) by establishing the long-range ferromagnetic order in V-doped WSe2 monolayer through free hole carriers. More importantly, the ferromagnetic order is clearly modulated by applying a back gate. Our findings open new opportunities for using two-dimensional transition metal dichalcogenides for future spintronics.Comment: 16 pages, 4 figure

Adsorptive Removal of Copper by Using Surfactant Modified Laterite Soil

Removal of copper ion (Cu2+) by using surfactant modified laterite (SML) was investigated in the present study. Characterizations of laterite were examined by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), inductively coupled plasma mass spectrometry (ICP-MS), and total carbon analysis. The optimum conditions for removal of Cu2+ by adsorption using SML were systematically studied and found as pH 6, contact time 90 min, adsorbent dosage 5 mg/mL, and ionic strength 10 mM NaCl. The equilibrium concentration of copper ions was measured by flame atomic absorption spectrometry (F-AAS). Surface modification of laterite by anionic surfactant sodium dodecyl sulfate (SDS) induced a significant increase of the removal efficiency of Cu2+. The surface modifications of laterite by preadsorption of SDS and sequential adsorption of Cu2+ were also evaluated by XRD and FT-IR. The adsorption of Cu2+ onto SML increases with increasing NaCl concentration from 1 to 10 mM, but at high salt concentration this trend is reversed because desorption of SDS from laterite surface was enhanced by increasing salt concentration. Experimental results of Cu2+/SML adsorption isotherms at different ionic strengths can be represented well by a two-step adsorption model. Based on adsorption isotherms, surface charge effects, and surface modification, we suggest that the adsorption mechanism of Cu2+ onto SML was induced by electrostatic attraction between Cu2+ and the negatively charged SML surface and nonelectrostatic interactions between Cu2+ and organic substances in the laterite

PHENOLIC COMPOUNDS FROM CALLISTEMON CITRINUS LEAVES AND STEMS

In the search for bioactive constituents from Vietnamese plants,  the leaves and stems of Callistemon citrinus (Curtis) Skeels were selected for chemical investigation. Phytochemical analysis of plant led to the isolation of eight phenolic compounds including two flavonoids (eucalyptine (1) and 8-demethyleucalyptine (2)), two alcohols (blumenol A (3), n-tetratriacontanol (4)), three benzoic acid derivatives (acid gallic (5), methyl gallate (6) protocatechuic acid (7)), one sterol (b-sitosterol (8)), and along with one sesquiterpene (2,6,10-bisabolatriene (9)). The structures of the natural compounds were determined by spectroscopic evidences including 1D- and 2D-NMR and ESI-MS

Effects of water scarcity awareness and climate change belief on recycled water usage willingness: Evidence from New Mexico, United States

The global water crisis is being exacerbated by climate change, even in the United States. Recycled water is a feasible alternative to alleviate the water shortage, but it is constrained by humans’ perceptions. The current study examines how residents’ water scarcity awareness and climate change belief influence their willingness to use recycled water directly and indirectly. Bayesian Mindsponge Framework (BMF) analytics was employed on a dataset of 1831 residents in Albuquerque, New Mexico, an arid inland region in the US. We discovered that residents’ willingness to use direct recycled potable water is positively affected by their awareness of water scarcity, but the effect is conditional on their belief in the impacts of climate change on the water cycle. Meanwhile, the willingness to use indirect recycled potable water is influenced by water scarcity awareness, and the belief in climate change further enhances this effect. These findings implicate that fighting climate change denialism and informing the public of the water scarcity situation in the region can contribute to the effectiveness and sustainability of long-term water conservation and climate change alleviation efforts

Determination of The Optimal Dosage of Chemical Compounds in the Wastewater Treatment Process in Trang Bach Coal Mine: the Laboratory Scale

The pH index of Trang Bach coal mine wastewater ranges from 2,8 to 6, meanwhile, the content of Fe, Mn, and turbidity & suspended solids (TSS) are rather high and it is impossible to discharge the wastewater directly to the environment. In order to achieve the requirement of QCVN 40:2011/BTNMT standard – The national standard for industrial wastewater quality after treatment of Vietnam and other purposes, the wastewater need to be treated by several methods such as coagulation-flocculation or sedimentation. In this article, we intend to find the optimal dosages of chemical compounds for the TSS, pH, Fe and Mn treatment process for Trang Bach coal mine wastewater in the laboratory modular

Spatially Resolved Cathodoluminescence in the Vicinity of Defects in the High-Efficiency InGaN/GaN Blue Light Emitting Diodes

In addition to the standard 447 nm blue emission from the InGaN/GaN multiple quantum wells, a high-energy shoulder is clearly observed in cathodoluminescence spectra of the high-efficiency InGaN/GaN blue light emitting diodes grown on sapphire substrates by metalorganic chemical vapor deposition. Monochromatic cathodoluminescence images of the samples measured at low temperature reveal a competition between the two emissions in the vicinity of the dislocations. The high-energy emission is dominant at the regions near the dislocation cores, while the blue emission is enhanced around the dislocation edges. The high-energy emission region is considered as a potential barrier that prevents the carriers for the blue emission from nonradiatively recombining at the dislocations

Porównanie zasobów węgla i popytu na węgiel w Wietnamie i Polsce w przeszłości oraz tego, jak zmieni się w przyszłości

The article in individual chapters discuss domestic coal resources in Poland and Vietnam, types of coal occurrence in both countries, the processing status and main domestic mining companies. The last part will be a comparison of mining prospects and plans for the development of coal mining in both countries and a summary of positive practices in both countries