On Bakhvalov-type meshes for a linear convection-diffusion problem in 2D

For singularly perturbed two-dimensional linear convection-diffusion problems, although optimal error estimates of an upwind finite difference scheme on Bakhvalov-type meshes are widely known, the analysis remains unanswered (Roos and Stynes in Comput. Meth. Appl. Math. 15 (2015), 531--550). In this short communication, by means of a new truncation error and barrier function based analysis, we address this open question for a generalization of Bakhvalov-type meshes in the sense of Boglaev and Kopteva. We prove that the upwind scheme on these mesh modifications is optimal first-order convergence, uniformly with respect to the perturbation parameter, in the discrete maximum norm. Furthermore, we derive a sufficient condition on the transition point choices to guarantee that our modified meshes can preserve the favorable properties of the original Bakhvalov mesh

On Bakhvalov-type meshes for a linear convection-diffusion problem in 2D

For singularly perturbed two-dimensional linear convection-diffusion problems, although optimal error estimates of an upwind finite difference scheme on Bakhvalov-type meshes are widely known, the analysis remains unanswered (Roos and Stynes in Comput. Meth. Appl. Math. 15 (2015), 531--550). In this short communication, by means of a new truncation error and barrier function based analysis, we address this open question for a generalization of Bakhvalov-type meshes in the sense of Boglaev and Kopteva. We prove that the upwind scheme on these mesh modifications is optimal first-order convergence, uniformly with respect to the perturbation parameter, in the discrete maximum norm. Furthermore, we derive a sufficient condition on the transition point choices to guarantee that our modified meshes can preserve the favorable properties of the original Bakhvalov mesh

Synthesis of Gold Nanoparticles Conjugated with Protein A: Towards the Application in Biosensors for Virus Detection

In this article, a facile and effective technique is described to prepare a complex of gold nanoparticles (GNPs)/protein A (PrA) for biosensors in virus detection. GNPs were synthesized by the reduction of tetrachloroauric (III) acid trihydrate using sodium ascorbate, and then coated with PrA via ultracentrifugation. The complex of GNPs/PrA was characterized using UV-vis spectroscopy and transmission electron microscopy. The immunogold labeling method of scanning electron microscopy was also used to verify the capacity for the detection and binding of GNPs/PrA to H$_{1}$N$_{1}$ influenza A virus particles. The results showed that GNPs were spherical, uniform shape, and approximately 10 nm in size. Noticeably, the complex of GNPs/PrA could detect and bind effectively to H$_{1}$N$_{1}$ influenza A virus particles by a large number of GNPs surrounded. The advantage of the complex of GNPs/PrA showed a highly potential application in biosensors with the improvement of the sensitivity and transducing signal for virus detection

KHẢO SÁT ĐIỀU KIỆN SẢN XUẤT BỘT QUẢ HỒNG ĐÀ LẠT (Diospyros kaki T.)

Tóm tắt: Hồng là một trong những loại quả có giá trị dinh dưỡng cao. Hiện nay, nhu cầu về sử dụng các sản phẩm bột trái cây cũng như dùng bột trái cây để chế biến thành các dạng sản phẩm khác là rất lớn. Nghiên cứu này sẽ khảo sát các điều kiện để sản xuất bột từ quả hồng sao cho giữ được các chất có hoạt tính sinh học đồng thời thu được bột hồng có chất lượng cảm quan cao. Kết quả cho thấy, khi quả hồng được chần bằng nước nóng 90°C trong thời gian 2 phút, sau đó sấy ở nhiệt độ 70°C đến hàm ẩm 3–4 %, để nguội và xay nghiền để thu được bột quả hồng thì sản phẩm có chất lượng cảm quan tốt nhất với hàm lượng polyphenol đạt 9,39 (mg GAE/g bột khô), hàm lượng flavonoid 10,29 (mg QE/g bột khô). Khả năng kháng oxy hóa 40,01 %, độ trương nở của bột 8,67 (ml/g bột khô). Bột thu được có chất lượng cảm quan tốt nhất.Từ khóa: quả hồng, polyphenol, flavonoid, khả năng kháng oxy hóa, bột hồn

The lasting effects of innovation on firm profitability: panel evidence from a transitional economy

This study is the first to study the lasting effects of innovation on firm profitability in Vietnam. Using a unique panel dataset for the period 2005–2015, our results show that innovators achieve higher profit in comparison with non-innovating firms. The positive effects of innovation on firm profitability are observed not only in the short term but also in the longer term. The benefits of innovation for firm profitability can be seen in higher export probability, better productivity, better access to formal credit, and the ability to secure government support, but only after innovation

Description of Geocenamus vietnamensis sp. n. (Nematoda : Merliniidae) from Vietnam

A new species of the genus Geocenamus was isolated from soil and root samples from the rhizosphere of Casuarina equisetifolia (Casuarinaceae) in Quang Nam province, Vietnam. This species is characterized by a round-to-hexagonal labial disc, the presence of a labial region, which is continuous or slightly offset from the body with six sectors, lateral sectors of first labial annulus being smaller than the submedian sectors, the presence of six to seven labial annules; the absence of deirids; stylet length 24 to 28 mu m long, body length 776 to 979 mu m long; lateral field with six to eight lateral lines, without areolation at mid-body and with areolation in outer bands at the tail region and a pointed tail terminus. Geocenamus vietnamensis n. sp. most closely resembles G. boghiae in having a non-sclerotized head framework and lacking a bursa in the males. It can be clearly distinguished from all other species of the genus Geocenamus by these characteristics. The combination of morphology, morphometric features, and phylogenetic trees, based on D2-D3 of 28S and ITS rDNA sequences, showed that this new species can be clearly separated from all other sequenced species. This record is the first for Geocenamus in Vietnam

Morphological and molecular characteristics of Pratylenchus haiduongensis sp. n., a new species of root-lesion nematodes associated with carrot in Vietnam

Pratylenchus haiduongensis sp. n. is described as associated with carrot (Daucus carota subsp. sativus (Hoffm.) Schubl. & G. Martens) in Hai Duong Province, Vietnam. P. haiduongensis sp. n. is characterized by the lip region with three annuli and slightly separated from the body. Stylet knobs are rounded (never indented anteriorly). The lateral field includes four incisures, bearing areolation at the pharynx region and tail region and occasionally appears in the vulval region. Sometimes the appearances of oblique broken striaes divide the lateral field into five or six incisures. The ovary is distinct with one row of oocytes. Spermatheca is oval in shape with round central cavity, without sperm or reduced in some specimens. The postvuval uterine sac is long surpassing the vulva body diameter by 2 to 2.5 times (PUS = 31 to 65 mm). High vulva position with V = 66 to 75%. The tail shape can be subhemispherical with a smooth, slightly indented, broadly smooth, or cleft terminus observed in some specimens. The matrix code of P. haiduongensis sp. n. is: A2, B1, C4, D(1,3), E1, F(5,6), G(1,2), H(1,4); I(1,2,3,4), J1, K(1,2) according to Castillo and Vovlas (2007). The LSU-D2D3 segment and the ITS-rDNA region of this species were amplified and sequenced. The morphological characters and molecular phylogenetic analyses confirmed that this is a new species of the genus Pratylenchus in Vietnam

EXTRACURRICULAR SPORTS: POPULAR CONTENTS AND FORMS AMONG STUDENTS IN THE DORMITORY OF VIETNAM NATIONAL UNIVERSITY HO CHI MINH CITY

This article is written to provide thorough information about popular contents and forms of extracurricular sports performed by university students at a dormitory of Vietnam National University Ho Chi Minh City (VNUHCMC). The study uses document references, surveys, and statistical mathematics to investigate what extracurricular sports are favored by the students and how they organize their practices. The results indicate that the majority of students choose to practice football, volleyball, badminton, athletics, and martial arts. They play with themselves and/or in teams, without instructors, from 30 minutes to 02 hours in the afternoon after school time and/or in the morning, at the dormitory and/or sports centers.  Article visualizations

PHYSICAL CONDITION OF MALE STUDENTS AT VIETNAM NATIONAL UNIVERSITY OF HO CHI MINH CITY DORMITORY

The purpose of the study is to provide information about the current physical condition of 19-year-old male students of the Vietnam National University of Ho Chi Minh City (VNUHCMC) dormitory. The research used the methods of synthesizing sport-related documents, interviewing experts, applying pedagogical tests, and statistical analysis to determine appropriate physical fitness assessment tests. Afterward, the figures for the physical condition of male students at the VNUHCMC dormitory were compared with that of the average Vietnamese people, of Hanoi National University (HNU), University of Danang (UD), Can Tho University (CTU), and Ho Chi Minh City (HCMC) students at the same age and gender, and with the standard shown in Decision 53/2008/BGDDT of the Ministry of Education and Training. The results show that the “good” group accounts for 28.75%, the “acceptable” group for 23.19% and the “failed” group for 48.06%. It is notable that the agility, leg muscular strength, endurance, and motor skills of 19-year-old male students at the VNUHCMC dormitory are greater than the average physical fitness of Vietnamese people, as well as students of the same age and gender at HNU, UD, and CTU. Their endurance is also higher than that of male HCMC pupils of the same age, but their leg muscular strength and motor abilities are almost comparable.  Article visualizations