Numerical study of the indentation formation of a compound droplet in a constriction

Hoe D. Nguyen,Truong V. Vu,Phan H. Nguyen,Binh D. Pham,Nang X. Ho,Cuong T. Nguyen,Vinh T. Nguyen 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.4

A compound droplet deforming in a constricted tube widely appears in drug delivery and microfluidic devices. In such a constriction, an indentation can present at the trailing surface of the droplet. However, this aspect has not been fully investigated and understood so far. This study focuses on the effects of some dimensionless parameters on the negative curvature, i.e., indentation, at the trailing surface of a compound droplet moving through a constricted tube. The presence of the constriction at the middle of the tube length enhances the droplet indentation. Numerical results were obtained for the capillary number Ca (varied in range of 0.1 - 1.0), the inner-to-outer droplet radius ratio R 21 (varied in range of 0.2 - 0.9), the droplet-to-tube radius ratio R 10 (varied in range of 0.2 - 0.9), the inner-to-outer interfacial tension coefficient ratio σ 21 (varied in range of 0.1 - 6.4), and the normalized depth of the constriction d/R (varied in range of 0.0 - 0.8). The results reveal that the most influencing factor is Ca, increasing its value leads to the increment of the maximum indentation at the trailing surface of the inner and outer droplets. The indentation is also increased with increasing the value of R 10and d/R. In contrast, increasing R 21 results in a decrease in the indentation at the trailing surface of the outer droplet. When increasing σ 21 , the indentation at the trailing surface of the inner one is quickly suppressed, while the outer droplet is minorly affected. We also point out the patterns of the trailing surface of the inner and outer droplets and their transitions from one to the other patterns in the diagrams based on these parameters.

Molecular-weight engineering of high-performing diketopyrrolopyrrole-based copolymer bearing high π-extended long donating units

Hoang, M.H.,Nguyen, D.N.,Ngo, T.T.,Um, H.A.,Cho, M.J.,Choi, D.H. IPC Science and Technology Press 2016 Polymer Vol.83 No.-

Two D-A alternating π-conjugated copolymers bearing diketopyrrolopyrrole (DPP) and sextetthiophene with different molecular weights were synthesized to investigate their physical properties and performance in thin-film transistors and photovoltaic cells. The solubility and molecular weight (MW) of these copolymers with a highly rigid backbone were improved by controlling the feeding ratio of the monomer in the polymerization mixture. These polymers exhibited high crystallinity with a predominant edge-on chain orientation on the substrate. The higher-MW P(DPP-6T)-2 copolymer displayed a higher hole mobility of 3.26 cm<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP> than the low-MW P(DPP-6T)-1 copolymer. Bulk heterojunction photovoltaic cells made of a blend of P(DPP-6T)-2 and (6,6)-phenyl C<SUB>71</SUB>-butyric acid methyl ester displayed good device performance with a power conversion efficiency of 4.68%.

Solid circulation characteristics of the three-reactor chemical-looping process for hydrogen production

Lee, D.,Seo, M.W.,Nguyen, T.D.B.,Cho, W.C.,Kim, S.D. Pergamon Press ; Elsevier Science Ltd 2014 International journal of hydrogen energy Vol.39 No.27

The three-reactor chemical-looping (TRCL) system for high purity hydrogen production and intrinsic CO<SUB>2</SUB> separation is an innovative concept using a circulating oxygen carrier. The process employs iron oxide as an oxygen carrier, via which a redox reaction takes place alternately within three reactors, i.e. a fuel reactor (FR), where the natural gas is combusted to CO<SUB>2</SUB> and H<SUB>2</SUB>O, a steam reactor (SR), where the steam is reduced to hydrogen, and an air reactor (AR), where the oxygen carrier returned to its original form by aeration. As it consists of three reactors (AR, FR, and SR) and a riser, the TRCL system has complicated hydrodynamic characteristics. In this study, a cold mode TRCL system with non-mechanical valve was designed and constructed to investigate the solid circulation characteristics. A series of hydrodynamic tests on the system was performed in which zirconia (d@?ρ=181μm, ρ<SUB>s</SUB> = 3850 kg/m<SUP>3</SUP>) was used as a bed material. The solid flow rate increased up to a maximum value with increasing gas velocity into the loop-seal. The gas leakages between AR and FR, and between FR and SR due to solid circulation were negligible. Furthermore, a two-dimensional (2D) computational fluid dynamics (CFD) simulation using a commercial CFD code was carried out in order to better understand the flow behavior of the gas solid mixture inside the TRCL system.

The Progression of SARS Coronavirus 2 (SARS-CoV2): Mutation in the Receptor Binding Domain of Spike Gene

Sinae Kim,Jong Ho Lee,Siyoung Lee,Saerok Shim,Tam T. Nguyen,Jihyeong Hwang,Heijun Kim,Yeo-Ok Choi,Jaewoo Hong,Suyoung Bae,Hyun Jhung Jhun,Hokee Yum,이영민,Edward D. Chan,Liping Yu,Tania Azam,Yong-Dae Kim 대한면역학회 2020 Immune Network Vol.20 No.5

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) is a positive-sense single-stranded RNA (+ssRNA) that causes coronavirus disease 2019 (COVID-19). The viral genome encodes twelve genes for viral replication and infection. The third open reading frame is the spike (S) gene that encodes for the spike glycoprotein interacting with specific cell surface receptor – angiotensin converting enzyme 2 (ACE2) – on the host cell membrane. Most recent studies identified a single point mutation in S gene. A single point mutation in S gene leading to an amino acid substitution at codon 614 from an aspartic acid 614 into glycine (D614G) resulted in greater infectivity compared to the wild type SARS-CoV2. We were interested in investigating the mutation region of S gene of SARS-CoV2 from Korean COVID-19 patients. New mutation sites were found in the critical receptor binding domain (RBD) of S gene, which is adjacent to the aforementioned D614G mutation residue. This specific sequence data demonstrated the active progression of SARS-CoV2 by mutations in the RBD of S gene. The sequence information of new mutations is critical to the development of recombinant SARS-CoV2 spike antigens, which may be required to improve and advance the strategy against a wide range of possible SARS-CoV2 mutations.

Hyperfine structure of Sc@C₈₂ from ESR and DFT

Morley, G W,Herbert, B J,Lee, S M,Porfyrakis, K,Dennis, T J S,Nguyen-Manh, D,Scipioni, R,van Tol, J,Horsfield, A P,Ardavan, A,Pettifor, D G,Green, J C,Briggs, G A D IOP Pub 2005 Nanotechnology Vol.16 No.11

<P>The electron spin <I>g</I>-?and hyperfine tensors of the endohedral metallofullerene Sc@C<SUB>82</SUB> are anisotropic. Using electron spin resonance (ESR) and density functional theory (DFT), we can relate their principal axes to the coordinate frame of the molecule, finding that the <I>g</I>-tensor is not axially symmetric. The Sc bond with the cage is partly covalent and partly ionic. Most of the electron spin density is distributed around the carbon cage, but 5% is associated with the scandium d<SUB><I>yz</I></SUB> orbital, and this drives the observed anisotropy. </P>

Genetic Status of Asiatic Black Bear (Ursus thibetanus) Reintroduced into South Korea Based on Mitochondrial DNA and Microsatellite Loci Analysis.

Kim, Yung-Kun,Hong, Yoon-Jee,Min, Mi-Sook,Kim, Kyung Seok,Kim, Young-Jun,Voloshina, Inna,Myslenkov, Alexander,Smith, Gavin J D,Cuong, Nguyen Dinh,Tho, Huynh Huu,Han, Sang-Hoon,Yang, Doo-Ha,Kim, Chang- published for the Association by Oxford University 2011 The Journal of heredity Vol.102 No.2

<P>The Asiatic black bear is one of the most endangered mammals in South Korea owing to population declines resulting from human exploitation and habitat fragmentation. To restore the black bear population in South Korea, 27 bear cubs from North Korea and Russian Far East (Primorsky Krai) were imported and released into Jirisan National Park, a reservoir of the largest wild population in South Korea, in 2004. To monitor the success of this reintroduction, the genetic diversity and population structure of the reintroduced black bears were measured using both mitochondrial and nuclear DNA markers. Mitochondrial D-loop region DNA sequences (615 bp) of 43 Japanese black bears from previous study and 14 Southeast Asian black bears in this study were employed to obtain phylogenetic inference of the reintroduced black bears. The mitochondrial phylogeny indicated Asiatic black bear populations from Russian Far East and North Korea form a single evolutionary unit distinct from populations from Japan and Southeast Asia. Mean expected heterozygosity (H(E)) across 16 microsatellite loci was 0.648 for Russian and 0.676 for North Korean populations. There was a moderate but significant level of microsatellite differentiation (F(ST) = 0.063) between black bears from the 2 source areas. In addition, genetic evidences revealed that 2 populations are represented as diverging groups, with lingering genetic admixture among individuals of 2 source populations. Relatedness analysis based on genetic markers indicated several discrepancies with the pedigree records. Implication of the phylogenetic and genetic evidences on long-term management of Asiatic black bears in South Korea is discussed.</P>

The evolutionary dynamics of highly pathogenic avian influenza H5N1 in south-central Vietnam reveals multiple clades evolving from Chinese and Cambodian viruses

Nguyen, T.H.,Than, V.T.,Thanh, H.D.,Nguyen, V.Q.,Nguyen, K.H.,Nguyen, D.T.,Park, J.H.,Chung, I.S.,Jeong, D.G.,Chang, K.T.,Oh, T.K.,Kim, W. Pergamon Press 2015 Comparative immunology, microbiology and infectiou Vol.42 No.-

In Vietnam, highly pathogenic avian influenza (HPAI), such as that caused by H5N1 viruses, is the most highly contagious infectious disease that has been affecting domestic poultry in recent years. Vietnam might be an evolutionary hotspot and a potential source of globally pandemic strains. However, few studies have reported viruses circulating in the south-central region of Vietnam. In the present study, 47 H5N1-positive samples were collected from both vaccinated and unvaccinated poultry farms in the South Central Coast region of Vietnam during 2013-2014, and their genetic diversity was analyzed. A common sequence motif for HPAI virus was identified at HA-cleavage sites in all samples: either RERRRKR/G (clades 2.3.2.1c and 2.3.2.1a) or REGRRKKR/G (clade 1.1.2). Phylogenetic analysis of HA genes identified three clades of HPAI H5N1: 1.1.2 (n=1), 2.3.2.1a (n=1), and 2.3.2.1c (n=45). The phylogenetic analysis indicated that these Vietnamese clades may have evolved from Chinese and Cambodian virus clades isolated in 2012-2013 but are less closely related to the clades detected from the Tyva Republic, Bulgaria, Mongolia, Japan, and Korea in 2009-2011. Detection of the coexistence of virus clades 2.3.2.1 and the very virulent 1.1.2 in the south-central regions suggests their local importance and highlights concerns regarding their spread, both northwards and southwards, as well as the potential for reassortment. The obtained data highlight the importance of regular identification of viral evolution and the development and use of region-specific vaccines.

Bacillus subtilis, essential oil, chromium and glucose as sow pack alters the performance, immune and stress on pregnant sows and piglets

Nguyen, D. H.,Lan, R.,Kim, I. Agricultural Research Communication Center 2017 Indian journal of animal research Vol.51 No.-

<P>A total of 26 (Landrace × Yorkshire) sows were randomly allotted to two experimental dietary treatments: 1) basal diet (CON); 2) CON plus 0.28% sow pack (SP) to determine the effect of Bacillus subtilis, essential oil, chromium and glucose as sow pack supplementation on sows and piglets. During the overall study, sows fed the SP diet increased body weight of sow after weanling and farrowing, sow back-fat thickness on d 110 , average daily gain of piglets, the level of immunoglobulin-G (IgG) and insulin on d 14 lactating and after weanling and decreased body weight loss, the level of cortisol and glucose on d 14 lactating as well as the level of cortisol after weanling 3 d (P less than 0.05). In conclusion, the results indicated that supplementation of sow pack diet increased performance of sows and piglets, IgG, insulin of blood and decreased the cortisol and glucose in the blood profiles of sows.</P>

A new lignan and a new alkaloid, and α-glucosidase inhibitory compounds from the grains of Echinochloa utilis Ohwi & Yabuno

Nguyen, T.T.,Nguyen, D.H.,Zhao, B.T.,Le, D.D.,Choi, D.H.,Kim, Y.H.,Nguyen, T.H.,Woo, M.H. Academic Press 2017 Bioorganic chemistry Vol.74 No.-

A new lignan, utilisin (1), and a new alkaloid, echinoutilin (2), together with eleven known compounds 3-13 were isolated from the grains of Echinochloa utilis Ohwi & Yabuno. Their structures were identified through the analysis of spectroscopic data. The absolute configuration of 2 was determined by Mosher's method. These compounds were evaluated for α-glucosidase inhibitory activity. Among them, compounds 2, 3 and 6 exhibited considerable α-glucosidase inhibitory activity with IC<SUB>50</SUB> values of 42.1+/-1.3, 58.9+/-3.7, and 40.9+/-1.1μM, respectively. The results indicate that the grains of E. utilis will be useful in the treatment of diabetes control agents.

Development of a microfluidic perfusion 3D cell culture system

Park, D H,Jeon, H J,Kim, M J,Nguyen, X D,Morten, K,Go, J S IOP 2018 Journal of micromechanics and microengineering Vol.28 No.4

<P>Recently, 3-dimensional <I>in vitro</I> cell cultures have gained much attention in biomedical sciences because of the closer relevance between <I>in vitro</I> cell cultures and <I>in vivo</I> environments. This paper presents a microfluidic perfusion 3D cell culture system with consistent control of long-term culture conditions to mimic an <I>in vivo</I> microenvironment. It consists of two sudden expansion reservoirs to trap incoming air bubbles, gradient generators to provide a linear concentration, and microchannel mixers. Specifically, the air bubbles disturb a flow in the microfluidic channel resulting in the instability of the perfusion cell culture conditions. For long-term stable operation, the sudden expansion reservoir is designed to trap air bubbles by using buoyancy before they enter the culture system. The performance of the developed microfluidic perfusion 3D cell culture system was examined experimentally and compared with analytical results. Finally, it was applied to test the cytotoxicity of cells infected with Ewing’s sarcoma. Cell death was observed for different concentrations of H<SUB>2</SUB>O<SUB>2</SUB>. For future work, the developed microfluidic perfusion 3D cell culture system can be used to examine the behavior of cells treated with various drugs and concentrations for high-throughput drug screening.</P>