TỔNG HỢP “XANH” GRAPHENE OXIDE DẠNG KHỬ VÀ KHẢO SÁT HOẠT TÍNH ĐIỆN HOÁ

In this work, we synthesized reduced graphene oxide nanosheets by reducing graphene oxide in aqueous solutions with ascorbic acid, which is non-toxic and environmentally friendly. This simple method shows a potential in the bulk production of graphene and graphene-based materials. In addition, the synthesized graphene was utilized to modify a glassy carbon electrode. The resulting electrode can simultaneously detect paracetamol and codeine phosphate with the differential pulse voltammetry method, and it opens up the possible practical application of modified electrodes.Trong nghiên cứu này, chúng tôi tổng hợp các tấm graphene oxide dạng khử thông qua quá trình khử graphene oxide trong nước bằng acid ascorbic không độc hại và thân thiện với môi trường. Phương pháp đơn giản này có tiềm năng trong sản xuất graphene và các vật liệu dựa trên graphene với lượng lớn. Ngoài ra, graphene tổng hợp đã được biến tính lên điện cực than thuỷ tinh, cho phép phân tích đồng thời paracetamol và codeine phosphate bằng phương pháp volt-ampere, sử dụng kỹ thuật xung vi phân, mở ra khả năng ứng dụng trong thực tế của điện cực biến tính

The contribution of geophysics to archaeology: a case study of an ancient canal of the Oc Eo culture in the Mekong Delta, Vietnam

Generally, underground ancient canals are infilled with alluvial materials, with the canal bed and substrate often having different resistivity values. This study aimed to determine the location and morphology of Malleret’s ancient canal 16 located to the southeast of the Ba The mountain, Mekong Delta, Vietnam by means of geophysical techniques. Two geophysical methods were used: electromagnetic profile and electric resisitivity tomography. A geoelectric structure 70 m long with 70–95 mS/m of apparent conductivity was found. On the electrical resistivity tomography section, a resistivity zone of 10–20 Ω∙m, 1–4 m deep, 70 m wide corresponds to the mentioned above geoelectric structure, which is in an asymmetric U-shape extending toward the southeast-ern bank of canal 16. Hand-augering confirmed that the canal bed is fully incised into Holocene sediments as a substrate which stretches down to the Pleistocene. The sediments are composed of loams mixed with plant re-mains with a resistivity ρ ~ 10–15 Ω∙m. Both of the canal banks at a depth of 5 m are made up of Holocene sedi-ments (ρ ~ 4–10 Ω∙m). The 14C measurements determined the age of the organic matter in the canal as being equal to 1210 ±85 BP, suggesting canal 16 ceased being operational at that time. The precise positioning of canal 16 on the ground surface, as well as identifying the morphology of the canal bed, were corroborated by geophysical techniques. The obtained results are of considerable value to archaeologists

In vitro antioxidant activity and bioactive compounds from Calocybe indica

Nowadays, the use of mushrooms in medicine is ubiquitous and has achieved particular success. The antioxidants in mushrooms can deactivate free radicals. This study assesses the antioxidant potential of mushroom Calocybe indica with the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging methods and the total antioxidant capacity. The mushroom’s ethanol extract exhibits acceptable activity with a low IC50 value (240.11 μg/mL), approximately 2.9 times lower than that of the mushroom Ophiocordyceps sobolifera extract. The ABTS scavenging rate of the extract is around 60% at 500 µg/mL, and the total antioxidant capacity is equivalent to 64.94 ± 1.03 mg of GA/g or 77.42 ± 0.42 μmol of AS/g.  The total phenolics, flavonoids, polysaccharides, and triterpenoids are equivalent to 29.33 ± 0.16 mg of GAE/g, 17.84 ± 0.11 mg of QUE/g (5.04 ± 0.04%), and 4.96 ± 0.04 mg of oleanolic acid/g, respectively. Specifically, the total triterpenoid content has been reported for the first time. The mushroom can have potential biomedical applications

Polysaccharide extraction from Myxopyrum smilacifolium trunk and its antioxidant capacity

As a traditional medicinal plant in Vietnam, Myxopyrum smilacifolium has been used for a long history to treat cough, nervous disorders, numbness, rheumatism, and cephalalgia. Nevertheless, reports on the antioxidant activity and extraction of M. smilacifolium polysaccharides are still very rare. This study was designed to extract a high yield of polysaccharides from the M. smilacifolium trunk and characterize it. As a result, the maximum yield of the polysaccharides of 5.13 ± 0.05% was obtained with an extraction time of three hours, extraction temperature of 100 oC, the ratio of water to sample of 1:50 as extraction solution, extraction number of times 3, and the ratio of ethanol to extract volume 5:1 (v/v). Polysaccharides was characterized by Fourier transform infrared spectroscopy (FT-IR) and high-performance gel-permeation chromatography (HPGPC). The average molecular weight of extracted polysaccharides was around 3.78 × 105 Da. In vitro assays dan impressive antioxidant activities of the extracted polysaccharides, containing 0.2423 ± 0.0028 mg GA/g or 0.2142 ± 0.0007 μmol AS/g. The IC50 values of polysaccharides in the DPPH and ABTS methods were 0.89 mg/mL and 3.85 mg/mL, respectively.  These findings exhibited the potential for application or further research and development of polysaccharides from Myxopyrum smilacifolium

In vitro antioxidant activity and content of bioactive compounds from Homalomena occulta

Homalomena occulta, a plant widely used in traditional Vietnamese medicine, was assessed for its antioxidant potential through DPPH radical scavenging and total antioxidant capacity methods. The results showed that Homalomena occulta exhibited significant antioxidant activities with a low IC50 value of 40.27 μg/mL, which is comparable to that of curcumin (38.50 μg/mL). Furthermore, the total antioxidant capacity of the Homalomena occulta extract was determined to be 77.48 ± 2.34 mg GA/g. To investigate the composition of the plant, various compounds including total phenolic, total flavonoid, polysaccharides, and triterpenoids were quantified using colorimetric methods with specific reagents. The content of phenolic compounds, flavonoid compounds, polysaccharides, and triterpenoids in Homalomena occulta was found to be 36.87 ± 0.42 GAE/g, 26.83 ± 0.29 mg QUE/g, 5.06 ± 0.06%, and 52.09 ± 1.77 mg Olenanoic/g, respectively. Notably, this study provides the first-ever report on the polysaccharide and total triterpenoid content of Homalomena occulta

TỔNG HỢP VÀ ĐẶC TRƯNG hydrogel glucomannan – poly(acrylic acid) NHẠY pH ĐỊNH HƯỚNG ỨNG DỤNG TRONG HỆ THỐNG PHÂN PHỐI 5-aminosalicylic acid CÓ KIỂM SOÁT

In this study, glucomannan-poly(acrylic acid) hydrogels were synthesized under different conditions. The hydrogels consist of glucomannan and acrylic acid and are crosslinked by N,N-methylene-bis-(acrylamide). The structure and morphology of the hydrogels were investigated by using Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM). The swelling ratio, biodegradation and pH-sensitive properties, relationship between hydrogel swelling rate and 5-ASA adsorption-desorption capacity, influence of medium pH on 5-ASA desorption, and 5-ASA adsorption kinetics were studied. The swelling ratio of the synthesized hydrogel samples is 16.70–56.21 times. This ratio is low in the pH 1.0 media and increases significantly in the pH 7,4 media. The hydrogels are biodegradable in the presence of cellulase (400 U·mg–1) in a pH 7.4 phosphate buffer at 37 °C (69.8% after ten days; the cellulase concentration 1.5 g·L­–1). The hydrogels exhibit high adsorption and desorption capacities for 5-ASA. The adsorption kinetics follows the pseudo-first-order model. These hydrogels can be applied to smart drug delivery systems.Trong nghiên cứu này, hydrogel glucomannan-poly(acrylic acid) đã được tổng hợp ở các điều kiện khác nhau với mục đích ứng dụng vào hệ thống phân phối thuốc 5-amiosalicylic acid (5-ASA) có kiểm soát. Hydrogel được tạo thành từ glucomannan và acrylic acid với tác nhân liên kết N,N-methylene-bis-(acrylamide). Cấu trúc và hình thái của hydrogel được nghiên cứu bằng phổ hồng ngoại chuyển dịch Fourier (FT-IR) và kính hiển vi điện tử quét (SEM). Tỷ lệ trương nở, tính chất phân huỷ sinh học và nhạy pH, mối quan hệ giữa tỷ lệ trương nở của hydrogel và khả năng hấp phụ-giải hấp 5-ASA, ảnh hưởng của pH môi trường để khả năng giải hấp 5-ASA và động học hấp phụ 5-ASA đã được nghiên cứu. Kết quả cho thấy tỷ lệ trương nở của các mẫu hydrogel là 16,70–56,21 lần. Tỷ lệ trương nở của hydrogel thấp ở môi trường pH 1 và tăng lên đáng kể trong môi trường pH 7,4.  Cellulase (400 U·mg–1) trong môi trường đệm pH 7,4 ở 37 °C có khả năng phân hủy sinh học hydrogel (69,8% sau 10 ngày; nồng độ cellulase 1,5 g·L–1). Hydrogel có cả khả năng hấp phụ và giải hấp tốt 5-ASA. Động học quá trình hấp phụ tuân theo mô hình biểu kiến bậc 1. Đây là vật liệu có tiềm năng ứng dụng trong phát triển hệ thống phân phối thuốc thông minh

Status Poles and Status Zoning to Model Residential Land Prices: Status-Quality Trade off Theory (Short Paper)

This study describes an approach for augmenting urban residential preference and hedonic house price models by incorporating Status-Quality Trade Off theory (SQTO). SQTO seeks explain the dynamic of urban structure using a multipolar, in which the location and strength of poles is driven by notions of residential status and dwelling quality. This paper presents in outline an approach for identifying status poles and for quantifying their effect on land and residential property prices. The results show how the incorporation of SQTO results in an enhanced understanding of variations in land / property process with increased spatial nuance. A number of future research areas are identified related to the status pole weights and the development of status pole index

Kinetics of neutralizing antibodies against Omicron variant in Vietnamese healthcare workers after primary immunization with ChAdOx1-S and booster immunization with BNT162b2

We studied the development and persistence of neutralizing antibodies against SARS-CoV-2 ancestral strain, and Delta and Omicron (BA.1 and BA.2) variants in Vietnamese healthcare workers (HCWs) up to 15 weeks after booster vaccination. We included 47 HCWs, including group 1 (G1, N = 21) and group 2 (G2; N = 26) without and with breakthrough Delta variant infection before booster immunization, respectively). The study participants had completed primary immunization with ChAdOx1-S and booster vaccination with BNT162b2. Neutralizing antibodies were measured using a surrogate virus neutralization assay. Of the 21 study participants in G1, neutralizing antibodies against ancestral strain, Delta variant, BA.1, and BA.2 were (almost) abolished at month 8 after the second dose, but all had detectable neutralizing antibodies to the study viruses at week 2 post booster dose. Of the 26 study participants in G2, neutralizing antibody levels to BA.1 and BA.2 were significantly higher than those to the corresponding viruses measured at week 2 post breakthrough infection and before the booster dose. At week 15 post booster vaccination, neutralizing antibodies to BA.1 and BA.2 dropped significantly, with more profound changes observed in those without breakthrough Delta variant infection. Booster vaccination enhanced neutralizing activities against ancestral strain and Delta variant compared with those induced by primary vaccination. These responses were maintained at high levels for at least 15 weeks. Our findings emphasize the importance of the first booster dose in producing cross-neutralizing antibodies against Omicron variant. A second booster to maintain long-term vaccine effectiveness against the currently circulating variants merits further research

THÀNH PHẦN HÓA HỌC VÀ HOẠT TÍNH CHỐNG OXY HÓA CỦA CÁC DỊCH CHIẾT TỪ HOA XUYẾN CHI (Bidens pilosa)

Bidens pilosa is used in traditional medicine in Vietnam. The antioxidant potential of the ethanol extract and fractions from the flowers of Bidens pilosa was evaluated through DPPH and ABTS radical scavenging and the total antioxidant capacity method. The ethyl acetate fraction exhibits the highest activity with the lowest IC50 value (IC50 = 31.54 μg·mL–1 and IC50 = 35.33 μg·mL–1 for DPPH and ABTS radical scavenging capacity), and the total antioxidant capacity was 85.05 ± 0.28 mg GA·g–1. The composition of Bidens pilosa flowers: the total phenolic, total flavonoid, polysaccharides, and triterpenoid, was examined by using the colorimetric method, and their quantities are equivalent to 59.35 ± 0.83 mg GAE·g–1, 42.35 ± 1.50 mg QE·g–1, 4.44 ± 0.02%, and 32.88 ± 0.66 mg acid oleanolic·g–1, respectively. Specifically, the polysaccharide and total triterpenoid content of Bidens pilosa flowers was reported for the first time.Xuyến chi đã được sử dụng trong các bài thuốc cổ truyền Việt Nam. Khả năng chống oxy hóa của cao toàn phần và các cao phân đoạn từ hoa cây Xuyến chi được đánh giá thông qua ba mô hình: tổng khả năng chống oxy hoá, khả năng bắt gốc tự do DPPH và khả năng bắt gốc ABTS. Kết quả cho thấy cao ethyl acetate có khả năng chống oxy hóa tốt nhất với IC50 nhỏ nhất (IC50 = 31,54 μg·mL–1 và           IC50 = 35,33 μg·mL–1 tương ứng với khả năng bắt gốc DPPH và ABTS) và hàm lượng các chất chống oxy hóa cao nhất (85,05 ± 0,28 mg·g–1 acid gallic). Hàm lượng các hợp chất có hoạt tính sinh học (tổng các hợp chất phenol, tổng flavonoid, tổng triterpenoid và polysaccharide) trong dịch chiết hoa cây Xuyến chi được xác định bằng phương pháp trắc quang. Hàm lượng tổng các hợp chất phenol và flavonoid là 59,35 ± 0,83 mg GAE·g–1 và 42,35 ± 1,50 mg QE·g–1; hàm lượng polysacharide và triterpenoid là 4,44 ± 0,02% và 32,88 ± 0,66 mg acid oleanolic·g–1. Lần đầu tiên, tổng hàm lượng triterpenoid và polysacharide trong hoa Xuyến chi được công bố