Research antioxidant activity of chitooligosacchride by UV-VIS absorption spectrocopy

Chitosan with 80% degree of deacetylation was hydrolyzed by cellulase of Trichoderma viride to prepare chitooligosaccharides (COSs) by the fractionation of the COSs with ultrafiltration membrane. The antioxidant activities of the COSs were clarified in this study by reducing power and free radical scavenging ability assay by UV-VIS absorption spectrum. The results show that the COS 1 (10,000-5,000 Da), COS 2 (5,000-3,000 Da), COS 3 (3,000-1,000 Da) and COS 4 (less than1,000 Da) segments have antioxidant properties.The antioxidant activitives of the COSs increased with the increment of concentration, and they also depended on molecular weight

Synthesis of Gold Nanoparticles Capped with Quaterthiophene for Transistor and Resistor Memory Devices

Recently, the fabrication of nonvolatile memory devices based on gold nanoparticles has been intensively investigated. In this work, we report on the design and synthesis of new semiconducting quaterthiophene incorporating hexyl thiol group (4TT). Gold nanoparticles capped with 4TT (4TTG) were prepared in a two-phase liquid-liquid system. These nanoparticles have diameters in the range 2–6 nm and are well dispersed in the poly(3-hexylthiophene) (P3HT) host matrix. The intermolecular interaction between 4TT and P3HT could enhance the charge-transport between gold nanoparticles and P3HT. Transfer curve of transistor memory device made of 4TTG/P3HT hybrid film exhibited significant current hysteresis, probably arising from the energy level barrier at 4TTG/P3HT interface. Additionally, the polymer memory resistor structure with an active layer consisting of 4TTG and P3HT displayed a remarkable electrical bistable behavior

A High-Performance Routing Protocol Based on Mobile Agent for Mobile Ad Hoc Networks

This paper presents a modification of a well-known routing protocol, namely Ad hoc On-Demand Distance Vector, as a solution to improve the performance of mobile ad hoc networks. We adapted the mobile agent technology as to novel metrics for routing in those networks. The metric is a function of the loss rate, the bandwidth and the end-to-end delay of the link. Indeed, we established a new tunable parameter to obtain a tradeoff between throughput and delay when computing the new metric. As a result, any routing protocol using this metric can al-ways choose a high-throughput and low-delay path between a source and a destination. Hence, the achievable performance of the mobile ad hoc networks has been improved remarkably with our modified routing protocol

A High-Performance Routing Protocol Based on Mobile Agent for Mobile Ad Hoc Networks

This paper presents a modification of a well-known routing protocol, namely Ad hoc On-Demand Distance Vector, as a solution to improve the performance of mobile ad hoc networks. We adapted the mobile agent technology as to novel metrics for routing in those networks. The metric is a function of the loss rate, the bandwidth and the end-to-end delay of the link. Indeed, we established a new tunable parameter to obtain a tradeoff between throughput and delay when computing the new metric. As a result, any routing protocol using this metric can al-ways choose a high-throughput and low-delay path between a source and a destination. Hence, the achievable performance of the mobile ad hoc networks has been improved remarkably with our modified routing protocol

Causes and Clinical Characteristics of Small Bowel Bleeding in Northern Vietnam

Aim. Causes, clinical features, and diagnostic approaches for small bowel (SB) bleeding were analyzed to derive recommendations in dealing with this clinical condition. Methods. We included 54 patients undergoing surgical treatment for SB bleeding, from January 2009 to December 2019. Detailed clinical data, diagnosis procedures, and causes of bleeding were collected. Results. Among 54 cases with SB bleeding, the most common causes were tumors (64.8%), followed by angiopathy (14.8%), ulcers (9.3%), diverticula (5.6%), tuberculosis (3.7%), and enteritis (1.9%). Most tumors (32/35 cases, 91.4%) and vascular lesions (8/8 cases, 100%) were located in the jejunum. The incidence of tumors was higher in the older (30/41 cases, 73.1%) than that in patients younger than 40 years of age (5/13 cases, 38.5%, P<0.01). Common initial findings were melena (68.5%) and hematochezia (31.5%). The overall diagnostic yield of computed tomographic enterography (CTE) was 57.4% (31/54 cases), with the figures for tumors, vascular lesions, and inflammatory lesions being 71.4% (25/35 cases), 62.5% (5/8 cases), and 12.5% (1/8 cases), respectively. Double-balloon enteroscopy (DBE) definitively identified SB bleeding sources in 16/22 (72.7%) patients. Conclusion. Tumors, angiopathy, ulcers, and diverticula were the most common causes of SB bleeding in Northern Vietnamese population. CTE has a high detection rate for tumors in patients with SB bleeding. CTE as a triage tool may identify patients before double-balloon enteroscopy because of the high prevalence of SB tumors

Antioxidant and UV-radiation absorption activity of aaptamine derivatives – Potential application for natural organic sunscreens

Antioxidant and UV absorption activities of three marine product originated - aaptamine derivatives including piperidine[3,2-b]demethyl(oxy)aaptamine (C1), 9-amino-2-ethoxy-8-methoxy-3H-benzo[de][1,6]naphthyridine-3-one (C2), and 2-(sec-butyl)-7,8-dimethoxybenzo[de]imidazo[4,5,1-ij][1,6]-naphthyridin-10(9H)-one (C3) were theoretically studied by density functional theory (DFT). Direct antioxidant activities of C1–C3 were firstly evaluated via their intrinsic thermochemical properties and radical scavenging activity of the potential antioxidants with the HOO●/HO● radicals via four mechanisms, including: hydrogen atom transfer (HAT), single electron transfer (SET), proton loss (PL) and radical adduct formation (RAF). Kinetic calculation reveals that HOO● scavenging in water is occurred via HAT mechanism with C1 (kapp, 7.13x106 M-1 s-1) while RAF is more dominant with C2 (kapp, 1.40x105 M-1 s-1) and C3 (kapp, 2.90x105 M-1 s-1). Antioxidant activity of aaptamine derivatives can be classified as C1 > C3 > C2. Indirect antioxidant properties based on Cu(I) and Cu(II) ions chelating activity were also investigated in aqueous phase. All three studied compounds show spontaneous and favorable Cu(I) ion chelating activity with DG0 being -15.4, -13.7, and -15.7 kcal.mol-1, whereas DG0 for Cu(II) chelation are -10.4, -10.8, and -2.2 kcal.mol-1 for C1, C2 and C3, respectively. In addition, all compounds show UVA and UVB absorption; in which the excitations are determined mostly as π-π* transition. Overall, the results suggest the potential applications of the aaptamines in pharmaceutics and cosmetics, i.e. as sunscreen and antioxidant ingredient.<br /