Search

A five-step procedure was used to synthesize four novel conjugates of AZT and adenosine with quinazolinone scaffold. In the last step, alkynes-1 of quinazolinone were coupled to adenosine azide and AZT by Click chemistry to yield the designed conjugates. Their structures were characterized by full-length data of spectra including 1H-, 13C-NMR and MS. Screening for their in vitro anti-inflammatory activity was performed using Murine macrophage RAW 264.7 cells. The relationship between structure and biological activity was also discussed.

The spreading of the East Vietnam Sea (EVS, also known as Bien Dong, or the South China Sea), leading to the occurrence of syn-spreading (33-16 Ma) and post-spreading (< 16 to present) volcanism. Syn-spreading magma making up thick layers of tholeiitic basalt with a geochemical composition close to the refractory and depleted mid-ocean ridge basalt (MORB) is mainly distributed inside the EVS basin. The post-spreading magma is widely distributed inside the basin and extended to South and SE China, Hainan island, Southern Laos (Bolaven), Khorat Plateau (Thailand), and Vietnam, showing the typical intraplate geochemistry. Basaltic samples were collected at many places in Indochina countries, Vietnam’s coastal and continental shelf areas, to analyze for eruption age, petrographical, geochemical, and isotopic composition to understand the similarities and differences in the mantle sources between regions. The results reveal that basalts from some areas show geochemical features suggesting they were derived subsequently by spinel peridotite and garnet peridotite melting, forming high-Si, low-Mg, and low-Ti tholeiitic basalt to low-Si, high-Mg, and high-Ti alkaline basalt with the trace element enrichment increasing over time. Other basalts have geochemical and isotopic characteristics unchanged over a long period. The post-spreading basalt’s radiogenic Sr-Nd-Hf-Pb isotopic compositions show different regional basalts distribute in the various fields regardless of eruption age, suggesting that their mantle source feature is space-dependent. The post-EVS spreading basalts expose the regional heterogeneity, reflecting the mixture of at least three components, including a depleted mantle (DM) represented by the syn-EVS spreading source, similar to the DUPAL-bearing Indian MORB source; an enriched mantle type 1 (EM1), and type 2 (EM2). The DM may interact and acquire either EM1 or EM2 in the sub-continental lithospheric mantle; as a result, different eruption at different area acquires distinct isotopic signature, reflecting the heterogeneous nature of the subcontinental lithospheric mantle. The study proposes a suitable mantle dynamic model that explains the EVS spreading kinematics and induced volcanism following the India - Eurasian collision from the Eocene based on the research outcomes.

During the joint Russian-Vietnamese studies in the East Vietnam Sea (known as Bien Dong or the South China Sea), manifestations of new hydrocarbon-accumulating zones were discovered; evidences of the presence of mineral indicators for solid minerals in shelf deposits were obtained; a unique zone, where accumulations of ferromanganese crusts and nodules have been formed, was revealed for the first time; evidence of unique properties of deep-water fine-dispersed carbonate sediments (which makes it possible to attribute them to an independent type of mineral resources of the East Vietnam Sea) were obtained; the ikaite mineral (that serves as an indicator of methane migration zones and cold marine paleo-conditions) was discovered in the Phu Khanh basin; heavy concentrates with indicators of rare forms of ore mineralization were collected; features of methane and mercury fluxes into the atmosphere, cultures of methane-oxidizing, oil-oxidizing and sulfate-reducing bacteria were registered for the first time within the study areas. New data on gravity and magnetic field anomalies along the shelf and slope of Vietnam have been obtained. The article presents the results of coastal geophysical and gasgeochemical research obtained in 2010–2020 within the Joint Russian-Vietnamese Laboratory for Marine Geosciences (POI FEB RAS - IMGG VAST). For the first time, anomalous methane fields (comparable to anomalies on the oil- and gas-bearing shelf and the gas hydrate-bearing slope of Sakhalin Island) were registered in the water column. The gravimagnetic survey was carried out on the central and southern shelf and the continental slope of Vietnam; the executed works supplemented the geophysical data, which had been obtained in the 80s–90s of the preceding century. The paper contributes to the Russia-Vietnamese program within the UN Decade of Ocean Sciences for Sustainable Development framework.

Tannery wastewater was considered as a heavily industrial wastewater with very high amount of wastewater discharged everyday but not well-treating. The tanning wastewater from producing process contains various high strength toxic chemicals which could do the inhibition for biological treatment process leading to low quality effluent. It is required to perform the pre-treatment process by physical–chemical treatment including coagulation and flocculation in order to reduce the content of toxic chemicals before biological treatment. This study focused on investigate on the performance of Poly Ferric Chloride (PFC) as a flocculant for flocculation process in tannery wastewater treatment due to its advantages which could apply in a wide range of industries to help remove materials suspended in water. The application of PFC was conducted in batch test to find the optimum conditions including pH, PFC dose, and rotation speed in term of treating tannery wastewater performance. In addition, a common flocculant polyaluminium chloride (PAC) was chosen to compare with PFC in term of treatment efficiency and cost effective. As the result, with 0.4 ml/l PFC, pH – 10.4 with 100 rpm spins, it reaches its efficient treatment COD process to 93,3%; NH4+ 90,4% and SO42- 79,2% with could easily promote a potential alternative flocculant with excellent performance but lower cost.

Optical character recognition (OCR) systems help to digitize paper-based historical achieves. However, poor quality of scanned documents and limitations of text recognition techniques result in different kinds of errors in OCR outputs. Post-processing is an essential step in improving the output quality of OCR systems by detecting and cleaning the errors. In this paper, we present an automatic model consisting of both error detection and error correction phases for OCR post-processing. We propose a novel approach of OCR post-processing error correction using correction pattern edits and evolutionary algorithm which has been mainly used for solving optimization problems. Our model adopts a variant of the self-organizing migrating algorithm along with a fitness function based on modifications of important linguistic features. We illustrate how to construct the table of correction pattern edits involving all types of edit operations and being directly learned from the training dataset. Through efficient settings of the algorithm parameters, our model can be performed with high-quality candidate generation and error correction. The experimental results show that our proposed approach outperforms various baseline approaches as evaluated on the benchmark dataset of ICDAR 2017 Post-OCR text correction competition.

In the last decades, scene text recognition has gained worldwide attention from both the academic community and actual users due to its importance in a wide range of applications. Despite achievements in optical character recognition, scene text recognition remains challenging due to inherent problems such as distortions or irregular layout. Most of the existing approaches mainly leverage recurrence or convolution-based neural networks. However, while recurrent neural networks (RNNs) usually suffer from slow training speed due to sequential computation and encounter problems as vanishing gradient or bottleneck, CNN endures a trade-off between complexity and performance. In this paper, we introduce SAFL, a self-attention-based neural network model with the focal loss for scene text recognition, to overcome the limitation of the existing approaches. The use of focal loss instead of negative log-likelihood helps the model focus more on low-frequency samples training. Moreover, to deal with the distortions and irregular texts, we exploit Spatial TransformerNetwork (STN) to rectify text before passing to the recognition network. We perform experiments to compare the performance of the proposed model with seven benchmarks. The numerical results show that our model achieves the best performance., Comment: Accepted to ICMLA 2020

This thesis is written as a requirement of the “Mechanical Engineering” Bachelor program at Vietnamese-German University. It reports the content of my working progress during the last exchange semester of the program at RUHR University, Bochum and Fraunhofer UMSICHT. Liquid thermophysical characteristics are critical in a variety of scientific research and industrial applications for exact knowledge of these qualities is required for design and a better understanding of technological procedures. Therefore, there is a need to investigate these properties. Determination of density, interfacial tension and viscosity under ambient pressure has available through several methods. However, to investigate these properties, previous methods require contact with sample, which consumes time or requires a certain amount of experimental substance. Additionally, data for these properties under high pressure is lacking. A method can be applied to provide contactless investigation of liquid drop under pressure is acoustic levitation. The aim is to commission an acoustic levitator to measure density, interfacial tension, and viscosity of liquids. First, the basic principle of acoustic levitation needed to understand the setup is explained. Then, recent developments of properties measurement using acoustic levitation is review. Next, the high-pressure acoustic levitator plant and its function is described. The limitations and restrictions of the setup is pointed out. Afterwards, methods and procedures for density, interfacial tension and viscosity are presented. Finally, the measurement of these properties is conducted, and the results are presented and discussed.

We apply the coherent potential approximation to study the three-component Falicov - Kimball model, in which single-component and two-component fermionic particles are mixed in an optical lattice. In the model, the heavy single-component fermionic particles are localized while the light two-component fermionic particles can hop in the lattice. At half-filling, two transitions from an insulator via a metallic state to a Mott insulator are found with increasing the particle correlations. By contrast, at third-filling, only one transition from the metallic state to the Mott insulating phase is observed for strong repulsive interactions. Our results are consistent with those obtained by the dynamical mean field theory as well as by the slave boson mean field approach.

This study aims to determine the governance factors that influence the scientific research output of lecturers through the application of PLS-SEM, in conjunction with ANOVA and t-test. Based on a survey of 398 lecturers in twelve higher education institutions (HEIs) in Vietnam, the psychometric properties of the scales measuring the considered dimensions of scientific research outputs were initially examined through the Exploratory Factor Analysis (EFA) procedure, prior to being input into the PLS-SEM model. The SEM model comprised six constructs for the scientific research outputs: scientific research objectives of HEIs, leadership, decentralization, policies for lecturers, support for scientific research activities, and resources for scientific research. The results reveal that resources for scientific research have the most impact on lecturers’ scientific research output, followed by policies for lecturers, support for scientific research activities, scientific research objectives of HEIs, and finally, leadership.

The metal-insulator phase transition diagrams of the Anderson - Hubbard model at half filling with the box and the Gaussian disorder distributions are obtained via typical-medium theory within an approximation to the equation of motion. The equations determining the boundary between the correlated metal, Mott insulator, and Anderson localization phases are derived. Our results are in good agreement with those found by the more sophisticated methods and indicate that on a qualitative level they do not depend on the choice of the above disorder distributions.

BackgroundVaricocele presents as the most frequent cause of infertility in men. Most reports showed that varicocelectomy has a significant impact on male fertility and reproductive outcome. This study aims to evaluate the safety and effectiveness of scrotal–inguinal microsurgical varicocelectomy in treating male infertility.MethodsWe prospectively studied preoperatively and postoperatively (at 3 and 6 months) 86 consecutive patients diagnosed with varicocele, abnormal semen parameters, and infertility, undergoing scrotal–inguinal microsurgical varicocelectomy. Semen test was performed before surgery and at 3 months and 6 months after surgery. The reproductive events were short-term followed up.ResultsThe median age of the patient was 32.9 ± 5.1 (20–43). Two cases (2.7%) had a minor infection of the scrotum incision, who were well treated by appropriate antibiotics. After operation, total sperm count and the percentage of motile sperms at 3 months and 6 months were significantly higher than those pre-varicocelectomy, respectively. In total, 26.7% (23/86) of all couples achieved a spontaneous pregnancy. Late complications such as testicular atrophy, hydroceles, and recurrent varicocele have not occurred.ConclusionsScrotal–inguinal microsurgical varicocelectomy is an acceptable method in treating male infertility due to high rate of reproductive outcomes and very low rate of complications.

A topological insulator doped with random magnetic impurities is studied. The system is modeled by the Kane-Mele model with a random spin exchange between conduction electrons and magnetic dopants. The dynamical mean-field theory for disordered systems is used to investigate the electron dynamics. The magnetic long-range order and the topological invariant are calculated within the mean-field theory. They reveal rich phases, where different magnetic long-range orders such as antiferromagnetic or ferromagnetic one can exist in the metallic or insulating phases, depending on electron and magnetic impurity fillings. It is found that insulator only occurs at electron half filling, quarter filling and when electron filling is equal to magnetic impurity filling. However, nontrivial topology is observed only in half-filling antiferromagnetic insulator and quarter-filling ferromagnetic insulator. At electron half filling, the spin Hall conductance is quantized and it is robust against magnetic doping, while at electron quarter filling, magnetic dopants drive the ground state from ferromagnetic topological insulator to ferromagnetic metal. The quantum anomalous Hall effect is observed only at electron quarter filling and dense magnetic doping.

Scientific conferences are the place where experts and academics come together to share innovative ideas and research. However, traditional conferences have two major issues: accessibility and sustainability. The sustainability aspect alone, driven by increased attention to the environmental impact of air travel, is increasing interest in online and virtual conferencing. In this research, we use the Mozilla Hubs social virtual environment (SVE) platform to investigate the potential of SVEs to create a social environment for remote participants, centered around co-watching live streaming video of conference talks. A user study was conducted at the UIST 2019 conference with a focus on understanding social interactions, user experience, design aspects, and motivation of attendance. We also conducted a small virtual poster session in Hubs. The results show that SVEs offered a reasonable experience for co-watching the conference talks remotely. Additionally, the virtual poster session improved the social connectivity between remote attendees, and the overall experience was rated as very satisfying. In this paper, we offer design suggestions and recommendations for more future studies.

OCR post-processing is an essential step to improve the accuracy of OCR-generated texts by detecting and correcting OCR errors. In this paper, the OCR texts are resulted from an OCR engine which is based on the attention-based encoder-decoder model for unconstrained Vietnamese handwriting. We identify various kinds of Vietnamese OCR errors and their possible causes. Detailed statistics of Vietnamese OCR errors are provided and analyzed at both character level and syllable level, using typical OCR error characteristics such as error rate, error mapping/edit, frequency and error length. Furthermore, the statistical analyses are done on training and test sets of a benchmark database to infer whether the test set is the appropriate representative of the training set regarding the OCR error characteristics. We also discuss the choice of designing OCR post-processing approaches at character level or at syllable level relying on provided statistics of studied datasets.

Within the coherent potential approximation we study the two-dimensional Haldane-Hubbard model, in which an interplay between topology and correlation effects is realized. The model essentially describes correlated electrons moving in a honeycomb lattice with zero net magnetic flux. The influence of the next-nearest-neighbor hopping and electron correlations on the metal-insulator transitions are investigated by monitoring the density of states at the Fermi level and the energy gap. The topological properties of the insulators is determined by the Chern number. With a given next-nearest-neighbor hopping, electron correlations drive the system from the topological Chern insulator to a metal, and then to the topologically trivial Mott insulator.

We study the half-filled mass-imbalanced Hubbard model with spatially alternating interactions on an optical bipartite lattice by means of the dynamical mean-field theory. The Mott transition is investigated via the spin-dependent density of states and double occupancies. The phase diagrams for the homogeneous phases at zero temperature are constructed numerically. The boundary between metallic and insulating phases at zero temperature is analytically derived within the dynamical mean field theory using the equation of motion approach as the impurity solver. We found that the metallic region is reduced with increasing interaction anisotropy or mass imbalance. Our results are closely relevant to current researches in ultracold fermion experiments and can be verified through experimental observations.

The ionic Hubbard model with spatially alternating interactions, which may be realized by cold atoms in optical lattices, is studied by mean of the coherent potential approximation. The paramagnetic phase diagram for the half-filled model at zero temperature is obtained. The possibility of enlarging an intermediate metallic region in the parameter space is addressed.