Anti-inflammatory tirucallane saponins from Paramignya scandens.

Phan, Nguyen Huu Toan,Thuan, Nguyen Thi Dieu,Ngoc, Ninh Thi,Thao, Nguyen Phuong,Kim, Sohyun,Koh, Young Sang,Thanh, Nguyen Van,Cuong, Nguyen Xuan,Nam, Nguyen Hoai,Kiem, Phan Van,Kim, Young Ho,Minh, Cha Pharmaceutical Society of Japan 2015 Chemical & pharmaceutical bulletin Vol.63 No.7

<P>Five new tirucallane saponins, paramignyosides A-E (1-5), were isolated from the water fraction of the Paramignya scandens stem and leaves. Their structures were elucidated on the basis of spectroscopic evidence including high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) and one dimensional (1D)- and 2D-NMR. The effects of isolated compounds on pro-inflammatory cytokines were evaluated by measuring the production of interleukin (IL)-12 p40, IL-6, and tumor necrosis factor-α (TNF-α) in lipopolysaccharide (LPS)-stimulated bone marrow-derived dendritic cells (BMDCs). Paramignyoside C (3) exhibited selective and potent inhibitory effect (IC50=5.030.19??M) on the production of IL-12 p40 comparable to that of the positive control, SB203580 (IC50=5.000.16??M). Further studies are required to confirm efficacy in vivo and the mechanism of anti-inflammatory effects.</P>

Bilayer tablets with sustained-release metformin and immediate-release sitagliptin: preparation and in vitro/in vivo evaluation

Nguyen Ngoc Nha Thao,Pham Duy Toan,Nguyen Duc Tuan,Trinh Thi Thu Loan 한국약제학회 2021 Journal of Pharmaceutical Investigation Vol.51 No.5

Purpose Diabetes mellitus, especially type II, is one of the most common chronic diseases. Its first-line oral treatment is metformin, commonly in combination with another agent such as sitagliptin, a dipeptidyl peptidase-4 inhibitor. The commercial combination is Janumet XR 50/500 mg, in which the extended-release metformin core tablet is coated with an immediaterelease layer of sitagliptin. However, the coating process with solvents and a high temperature might affect the sitagliptin properties and product quality. Hence, the present study aimed to develop bilayer matrix tablets incorporating both drugs into two separate layers, a sustained-release metformin layer, and an immediate-release sitagliptin layer. Methods Wet granulation and direct compression methods were used for the metformin and sitagliptin layer, respectively. The optimal formulation was selected and characterized based on the design of experiments method. In vitro release and in vivo bioequivalence studies were also conducted to compare with the reference Janumet XR 50/500 mg. Results The optimized formulation immediately released sitagliptin (> 95%) within 30 min at pH 1.2 and sustained the release metformin for 10 h at pH 6.8. The in vivo behaviors of the bilayer tablets were bioequivalent to the commercial product, Janumet XR 50/500 mg. Conclusion The bilayer tablets could provide an alternative approach for combination therapy of type II diabetes.

Does Bribery Sand the Wheels? New Evidence from Small and Medium Firms in Vietnam

NGUYEN, Toan Ngoc Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.4

This research aims to revisit the hypothesis that bribery hurts firm performance in the context of a perceptibly corrupt country. Specifically, we use micro-data from Vietnamese small and medium firm surveys in 2013 and 2015 to examine whether bribery impedes firm revenue growth and labor productivity growth. An issue arising in this type of research is the potential endogeneity between firm bribing behaviors and firm performance. To go around the issue, we follow the literature to instrument bribery variable with the average probability of bribery in other provinces. We further employ the Analysis of Variance technique (ANOVA) to unveil if the effect of bribery is dependent on bribing purposes. The regression results show that firm performance is significantly influenced by firm size, firm age and firm bribing behavior. Larger firms are more likely to grow faster while firm performance tends to be negatively related to firm age. Particularly, we find that bribery significantly impedes firm revenue growth and labor productivity growth. The analysis of variance shows that the effect of bribery on firm performance may vary across bribing purposes. Our findings, therefore, support the sand-the-wheels hypothesis that bribery hurts firm performance even in a highly corrupt business environment.

N-doped Cdot/PtPd nanonetwork hybrid materials as highly efficient electrocatalysts for methanol oxidation and formic acid oxidation reactions

Nguyen, Van-Toan,Tran, Quoc Chinh,Quang, Nguyen Duc,Nguyen, Ngoc-Anh,Bui, Van-Tien,Dao, Van-Duong,Choi, Ho-Suk Elsevier 2018 Journal of alloys and compounds Vol.766 No.-

<P><B>Abstract</B></P> <P>The improvement of the catalytic performance for methanol and formic acid oxidation reactions remains a key issue for the development of a new generation of direct methanol and formic acid fuel cells. This study reports a simple approach, using selective chemical etching for the synthesis of unique nitrogen-doped carbon dot/Pt<SUB>84</SUB>Pd<SUB>16</SUB> (N-Cdot/Pt<SUB>84</SUB>Pd<SUB>16</SUB>) nano-network structure at room temperature with excellent electrocatalytic properties. The obtained nano-network hybrid material exhibits significant enhancement of the electrocatalytic activity for the electro-oxidation reaction of both methanol and formic acid with current densities of 999.0 and 1919.5 mA/mg<SUB>metal</SUB>, respectively, compared with the commercial ones of 751.32 and 806.02 mA/mg<SUB>metal</SUB>, respectively. Furthermore, the N-Cdot/Pt<SUB>84</SUB>Pd<SUB>16</SUB> nano-network hybrid materials exhibit excellent stability and hydrophilic dispersibility at room temperature.</P> <P><B>Highlights</B></P> <P> <UL> <LI> N-Cdot/PtPd nanonetwork hybrid material is synthesized at room temperature. </LI> <LI> A simple coreduction and a selective chemical etching are applied to the synthesis. </LI> <LI> It generates a nano-network structure with excellent electrocatalytic properties. </LI> <LI> N-Cdot functions as a uniform interconnection between the nanohybrid materials. </LI> <LI> The hybrid exhibits significant enhancement of the activity for both MOR and FAOR. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Plasma-treated sponge-like NiAu nanoalloy for enhancing electrocatalytic performance in hydrogen evolution reaction

Nguyen, Ngoc-Anh,Nguyen, Tham Thao-Trang,Nguyen, Van-Toan,Ali, Yousuf,Sim, Eunju,Choi, Ho-Suk Elsevier 2019 CATALYSIS TODAY - Vol.337 No.-

<P><B>Abstract</B></P> <P>We report a method for synthesizing a plasma-treated sponge-like NiAu nanoalloy to enhance the hydrogen evolution reaction (HER) performance. First, an as-prepared sponge-like NiAu nanoalloy is obtained by using NaBH<SUB>4</SUB> to reduce a NiCl<SUB>2</SUB> and HAuCl<SUB>4</SUB> mixture without using any surfactant. Second, this as-prepared sponge-like NiAu nanoalloy is treated by argon plasma under atmospheric pressure with a treatment time of 15 min to obtain the final plasma-treated sponge-like NiAu nanoalloy. The HER electrocatalytic performance of the plasma-treated sponge-like NiAu nanoalloy is then investigated in 0.5 M H<SUB>2</SUB>SO<SUB>4</SUB> electrolyte. From the results, the plasma-treated sponge-like NiAu nanoalloy exhibits enhanced HER performance compared to the as-prepared sponge-like NiAu nanoalloy due to the exposure of more active/edge sites. The overpotential at a current density of 10 mA.cm<SUP>−2</SUP> of the plasma-treated sponge-like NiAu nanoalloy (88 mV) is lower than that of the as-prepared sponge-like NiAu nanoalloy (134 mV), and this is due to the plasma treatment process. In addition, plasma-treated sponge-like NiAu nanoalloy shows an excellent durable ability of HER activity for 80,000 s.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Sponge-like NiAu nanoalloys are prepared using a simple method without any surfactant. </LI> <LI> Electronic coupling between Ni and Au atoms can improve the HER activity. </LI> <LI> The plasma-treated sponge-like NiAu nanoalloy exhibits enhanced HER performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Graphene dot armored PtMo nanosponge as a highly efficient and stable electrocatalyst for hydrogen evolution reactions in both acidic and alkaline media

Nguyen, Van-Toan,Nguyen, Ngoc-Anh,Ali, Yousuf,Tran, Quoc Chinh,Choi, Ho-Suk Elsevier 2019 Carbon Vol.146 No.-

<P><B>Abstract</B></P> <P>A new type of three-dimensional PtMo nanosponge wrapped with graphene dots (abbreviated as 3D Pt<SUB>x</SUB>Mo<SUB>1-x</SUB>@graphene) has been developed for catalyzing the hydrogen evolution reaction (HER). The graphene-dot wrapping takes place via the exfoliation of carbon dots during the co-reduction of Pt/Mo precursors and carbon dots at a low temperature in an aqueous solution. The synergistic effects of inner metallic alloy networks and outer graphene dots in the 3D Pt<SUB>x</SUB>Mo<SUB>1-x</SUB>@graphene are responsible for the outstanding HER performance and superb durability in both acidic and alkaline electrolytes. The 3D Pt<SUB>x</SUB>Mo<SUB>1-x</SUB>@graphene shows a low Tafel slope of 32 mV/dec and 51 mV/dec together with a low overpotential of 32 mV and 97 mV at a current density of −10 mA cm<SUP>−2</SUP> in acidic and alkaline media, respectively. The catalyst also shows superb stability, as confirmed by a large amount of repeated potential cycling exceeding 5000 cycles in acidic solution and long-term durability of over 50,000 seconds in an alkaline solution. This work provides a new feasible mean of synthesizing graphene-dot-wrapped Pt-based nanostructures with highly efficient catalytic activity and superb stability for HER without the need for surfactants or stabilizers.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

The Effect of Bribery on Firm Innovation: An Analysis of Small and Medium Firms in Vietnam

NGUYEN, Toan Ngoc Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.5

This study aims to provide empirical evidence on the causal relationship between bribery and firm innovation. To this end, we use a micro-dataset of small and medium firms in Vietnam surveyed in 2015. Given the binary nature of the dependent variable, a simple probit regression model is employed. However, as bribery variable is potentially endogenous, a simple probit regression may give biased estimates. We deal with the potential endogeneity by making use of the bivariate probit model. A property of the bivariate probit model is that it can produce efficient estimates of a typical probit model with endogenous binary explanatory variable. A Hausman-like likelihood ratio test is implemented following the estimation to test the existence of endogeneity. We find that bribery significantly undermines firm innovation. Also, firms run by household appear less innovative. The probability of innovation diminishes significantly if firm owners or managers have previous experience in firm products. As expected, larger firms seem to be more innovative. Exporters tend to be more innovative compared to non-exporters. Our findings provide support to the hypothesis that bribery is detrimental to firm innovation and, thus, innovation may be a mediating channel, through which, bribery impedes firm long-term performance.

Enhancement of Transduction Performance of a Dielectric Elastomer Actuator Based on Acrylonitrile Butadiene Rubber

Canh Toan Nguyen,Ngoc Linh Nguyen,이형석,김대경,이충한,문형필,구자춘,남재도,한정헌,최혁렬 한국고분자학회 2013 Macromolecular Research Vol.21 No.1

The synthetic elastomer based on acrylonitrile butadiene rubber (NBR) has been recently developed as a kind of dielectric elastomer actuators (DEAs). Its advantages are that its properties can be modified according to the requirements of applications. In this paper, we report a comprehensive study on the effects of plasticizers including diisodecyl phthalate (DIDP), dioctyladipate (DOA), and dioctyl phthalate (DOP) as well as a high dielectric additive,which is, barium titanate (BaTiO3) with respect to the overall performance of the synthetic elastomer. We investigate how the significant parameters representing the actuator performance can be changed according to the composition of the additives and how the actuation performances can be improved. In addition, we address how the environmental conditions such as exposure to the light and the air have influence on the properties of the synthetic elastomer, and a method for extending the lifetime of DEA is also addressed.

Factors Affecting Industry 4.0 Adoption on Studying ofSstudents : : An Study in Universities in Ho Chi Minh City, Vietnam

Truong Xuan NGUYEN,Toan Thanh NGUYEN,Hai Ngoc NGUYEN,Linh Thuy HOANG,Trung Vy CHAU 한국유통과학회 2018 KODISA ICBE (International Conference on Business Vol.2018 No.-

The study developed and tested the impact of occupation relevance, facility conditions, and social influence, skills on the actual use industry 4.0 on studying of students in universities in Ho Chi Minh City, Viet Nam. Both qualitative and quantitative methodologies were utilized in this study. Qualitative research first carried out with an in-depth interview, conducted to derive measurement items for the interested variables. Quantitative research used cross-sectional field design by pilot study and official study. The result of structural equation modeling showed that occupation relevance, skills, facility conditions, and social influence impacted the intermediates variables relevance advantage, perceived usefulness, behavioral intention to use, and actual to use. The occupation relevance, skills, facility conditions, and social influence are independent variables. They impact actual to use through mediating variables such as relevance advantage, perceived usefulness, and behavioral intention to use.

X-ray absorption spectroscopies of Mg-Al-Ni hydrotalcite like compound for explaining the generation of surface acid sites

Hong Khanh Dieu Nguyen,Toan Dang Nguyen,Dung Ngoc Hoang,Duc Sy Dao,Thao Tien Nguyen,Limphirat Wanwisa,Lan Linh Hoang 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.2

Hydrotalcite-like compound containing metal cations such as Mg2+, Al3+ and Ni2+ was characterized using Ni K-edge EXAFS and in situ Ni K-edge XANES techniques for clarifying its bonding environment around Ni2+ sites and structure changes during calcination from room temperature to 550 oC, respectively. At the fixed molar ratio of Mg/Ni/Al of 2/1/1, the results obtained from EXAFS analysis showed a slight blue shift before and after the calcination at 550 oC and a reduction in white line peak; the best fits of the two samples revealed tiny change in coordination number about 7 for Ni-O path but considerable difference for Ni-Mg(Al) path from about 4.5 to 9.5, confirming a modification from brucite like to mixed oxide structure. On the other hand, bond distances of the Ni-O and Ni-Mg paths nearly fixed at about 2.06 Å to 3.0 Å reflected stability of the cationic bond order on each plane, but partial collapse and decomposition of the interlayer formed by water molecules and anion CO3 2− after the calcination. Linear combination fit extracted from the in situ Ni K-edge XANES also confirmed the changes along with the calcination such as slow and fast decreases of brucite fraction at 150 oC and 330 oC, respectively, in corresponding to the mixed oxide fraction increases. The achieved bonding structures were also applied to explain acid-base occurrence of the hydrotalcite-like material, especially the acid sites generated by different static charges along with the bonds. The explanation was illustrated by NH3-TPD method.