On conformally flat circle bundles over surfaces

We study surface groups $\Gamma$ in $SO(4,1)$, which is the group of Mobius tranformations of $S^3$, and also the group of isometries of $\mathbb{H}^4$. We consider such $\Gamma$ so that its limit set $\Lambda_\Gamma$ is a quasi-circle in $S^3$, and so that the quotient $(S^3 - \Lambda_\Gamma) / \Gamma$ is a circle bundle over a surface. This circle bundle is said to be conformally flat, and our main goal is to discover how twisted such bundle may be by establishing a bound on its Euler number. By combinatorial approaches, we have two soft bounds in this direction on certain types of nice structures. In this article we also construct new examples, a "grafting" type path in the space of surface group representations into $SO(4,1)$: starting inside the quasi-Fuschsian locus, going through non-discrete territory and back.Comment: 28 pages, 7 figures. Updated from Thesis version: more correct bound of (3/2)n^2, updated exposition in section 3.

Formation of high-quality Ag-based ohmic contacts to p-type GaN

Low resistance and high reflectance ohmic contacts on p-type GaN were achieved using an Ag-based metallization scheme. Oxidation annealing was the key to achieve ohmic behavior of Ag-based contacts on p-type GaN. A low contact resistivity of similar to 5x10(-5) Omega cm(2) could be achieved from Me (=Ni, Ir, Pt, or Ru)/Ag (50/1200 angstrom) contacts after annealing at 500 degrees C for 1 min in O(2) ambient. Oxidation annealing promoted the out-diffusion of Ga atoms from the GaN layer, and Ga atoms dissolved in the in-diffused Ag layer with the formation of Ag-Ga solid solution, resulting in ohmic contact formation. Using Ru/Ni/Au (500/200/500 angstrom) overlayers on the Me/Ag contacts, the excessive incorporation of oxygen molecules into the contact interfacial region, and the out-diffusion and agglomeration of Ag, were effectively prevented during oxidation annealing. As a result, a high reflectance of 87.2% at the 460 nm wavelength and a smooth surface morphology could be obtained simultaneously. (C) 2008 The Electrochemical Society.open111618sciescopu

Reproductive biology of sagor catfish (Hexanematichthys sagor Hamilton, 1822) in Can Gio water, Vietnam

835-840Sagor catfish (Hexanematichthys sagor Hamilton, 1822) is one of the most popular fish caught in Can Gio reserve biosphere. A study on reproductive biology was conducted to evaluate the reproductive parameters, including male–female distinction, gonadal development stages, sex ratio, spawning season, fecundity, and size at first sexual maturity. The results showed that the number of males and females in the nature was not significantly different. Male and female fish can be distinguished when they reach the mature size. Gonadal of the fish pass through five stages of maturation. The histological screening of gonad, percentage of maturation stage and gonadal somatic index value of the fish showed all year round spawning with a peak of spawning female from March to August. The length at first sexual maturity of the fish is 25.39 cm. Fecundity ranged from 60 to 145 ovaries/individuals strongly related to weight and length. The current findings provide the scientific foundation for the purpose of fishery resource management and artificial breeding of the blue sagor catfish

TỔNG QUAN VỀ VIỆC SỬ DỤNG SELEN (Se) TRONG NUÔI TRỒNG THỦY SẢN

Effects of antibiotics usage in aquaculture on environment and human health has prompted the search for alternative products. Recently, the microelements in organic form have been used as alternative to antibiotics in aquaculture. Se is one of the microelements that have received heightened attention. This report reviews the role of Se in the culture of fishes (cobia Rachycentron canadum L., red sea bream Pagrus major, fingerling channel catfish Ictalurus punctatus, seabass Lates calcarifer, snubnose dart Trachinotus blochii, rainbow trout Oncorhynchus mykiss, common carp Cyprinus carpio L., Atlantic salmon parr Salmo salar, nile tilapia Oreochromis niloticus, african catfish Clarias gariepinus, Senegalese sole Solea senegalensis, grouper Epinephelus malabaricus, gilthead seabream Sparus aurata, Chinook salmon Oncorhynchus tshawytscha, fathead minnow Pimephales promelas, striped bass Morone saxatilis, bluegill Lepomis macrochirus, crucian carp Carassius auratus gibelio) and crustacean (giant freshwater prawn Macrobrachium rosenbergii, white shrimp Penaeus vannamei, marron Cherax cainii, crayfish Procambarus clarkii). Suggestion for further research on the application of Se in aquaculture is also included.Ảnh hưởng của kháng sinh trong nuôi trồng thủy sản lên môi trường và sức khỏe con người đã thúc đẩy các nghiên cứu tìm ra các sản phẩm thay thế. Gần đây, các nguyên tố vi lượng ở dạng hữu cơ đang được quan tâm sử dụng để thay thế kháng sinh trong nuôi trồng thủy sản. Selen là một trong những yếu tố vi lượng được quan tâm nhiều nhất. Báo cáo này tổng quan vai trò của Selen trong nuôi một số loài cá (cá giò Rachycentron canadum L., cá tráp đỏ Pagrus major, cá da trơn Ictalurus punctatus, cá chẽm Lates calcarifer, cá chim vây vàng Trachinotus blochii, cá hồi vân Oncorhynchus mykiss, cá chép Cyprinus carpio L., cá hồi Atlantic Salmo salar, cá rô phi Oreochromis niloticus, cá trê phi Clarias gariepinus, cá bơn Solea senegalensis, cá mú Epinephelus malabaricus, cá tráp đầu vàng Sparus aurata, cá hồi Chinook Oncorhynchus tshawytscha, cá tuế đầu bẹp Pimephales promelas, cá striped bass Morone saxatilis, cá bluegill Lepomis macrochirus, cá diếc Carassius auratus gibelio) và giáp xác (tôm càng xanh Macrobrachium rosenbergii, tôm thẻ chân trắng Penaeus vannamei, tôm hùm nước ngọt Cherax cainii, tôm hùm nước ngọt Procambarus clarkii). Báo cáo cũng đề xuất nghiên cứu tiếp theo về ứng dụng của Selen trong nuôi trồng thủy sản

Indium as an efficient ohmic contact to N-face n-GaN of GaN-based vertical light-emitting diodes

We propose indium (In), a low work function and nitride-forming element, as an efficient ohmic contact layer to N-face n-GaN. While conventional Al-based ohmic contacts show severe degradation after annealing at 300 C, In-based ohmic contacts display considerable improvement in contact resistivity. The annealing-induced enhancement of ohmic behavior in In-based contacts is attributed to the formation of an InN interfacial layer, which is supported by x-ray photoemission spectroscopy measurements. These results suggest that In is of particular importance for application as reliable ohmic contacts to n-GaN of GaN-based vertical light-emitting diodes.open3

ẢNH HƯỞNG CỦA ASTAXANTHIN BỔ SUNG TRONG THỨC ĂN LÊN TĂNG TRƯỞNG, TỶ LỆ SỐNG VÀ MÀU SẮC DA CÁ KHOANG CỔ NEMO, Amphiprion ocellaris THƯƠNG MẠI

This study examined the influence of astaxanthin added to food on growth, survival rate and pigmentation of commercial false clownfish, Amphiprion ocellaris. Five experiments were performed with synthetic astaxanthin contents: 0; 50; 100; 150 and 200 mg/kg diets. Mean weight and mean length of fish were 1.16 ± 0.22 gand and 33.05 ± 3.29 mm respectively. Fish were fed by 5% of their live weight during the examination of 8 weeks. After 56 days of experiments, the skin pigmentation levels were analysed using Clownfish Exercise pigmentation chart which has a scale from 1 to 10. Color scales of 5 experiments: 0; 50; 100; 150 and 200 mg Astaxanthin/kg diets were 2.12 ± 0.08, 3.79 ± 0.1, 5.31 ± 0.14, 7.78 ± 0.09, 8.04 ± 0.12 respectively. The result showed that the dietary astaxanthin could increase coloration of skin compared with the control group which had the lightest color (P 0.05) but there were no significant effects on growth and survival rate of clownfish (P 0.05).Nghiên cứu này đánh giá ảnh hưởng của Astaxanthin bổ sung trong thức ăn lên tăng trưởng, tỷ lệ sống và màu sắc da của cá khoang cổ Nemo Amphiprion ocellaris thương mại. Năm lô thí nghiệm được thực hiện với hàm lượng astaxanthin tổng hợp (Carophyll Pink 10% CWS) bổ sung vào trong thức ăn là: 0, 50, 100, 150 và 200 mg/kg. Cá thí nghiệm có khối lượng và chiều dài trung bình ban đầu tương ứng là 1,16 ± 0,22 g và 33,05 ± 3,29 mm. Cá được cho ăn với khẩu phần 5% khối lượng thân trong 8 tuần. Sau 56 ngày nuôi màu sắc da của cá được đánh giá bằng phương pháp cho điểm sử dụng thước so màu Clownfish Exercise có thang điểm từ 1 tới 10. Thang điểm màu sắc của 5 lô bổ sung 0, 50, 100, 150 và 200 mg Astaxanthin/kg thức ăn lần lượt là: 2,12 ± 0,08; 3,79 ± 0,1; 5,31 ± 0,14; 7,78 ± 0,09; 8,04 ± 0,12. Kết quả cho thấy những lô thí nghệm có bổ sung Astaxanthin làm tăng màu sắc da của cá so với lô đối chứng (P0,05) nhưng không có sự khác biệt có ý nghĩa về tăng trưởng và tỷ lệ sống giữa các lô thí nghiệm với nhau (P 0,05)

Short range scattering effect of InAs quantum dots in the transport properties of two dimensional electron gas

Short range interaction between two dimensional electron gas (2DEG) and InAs quantum dots embedded in the GaAs/AlGaAs quantum well is investigated as a function of carrier density. At low carrier density the interaction is significantly characterized by a transport to quantum lifetime ratio of less than 5. However, with an increase in carrier density, quantum lifetime is observed to undergo a sharp transition from 0.17 to 0.25 ps. This is attributed to the screening of short range repulsive scattering due to InAs quantum dots by the 2DEG.open7

Effect of enriching live feeds with HUFA on growth and survival of clownfish Amphiprion ocellaris (Cuvier, 1830) larvae

The aims of this study was to evaluate the effect of HUFA-enriched live feed in rearing Nemo fish larvae (Amphiprion ocellaris), 5 treatments were set up (each treatment was repeated in triplicate) with 5 concentrations of HUFA (Super Selco) (0, 50, 100, 150 and 200 ppm). After 45 days of culture with HUFA-enriched live feeds of different concentrations, the total length-TL as well as the specific growth rate (SGRL) in body length and survival rate of Nemo fish larvae in the treatments had significant differences (p 0.05). In the enriched live prey diet of 100 ppm Selco, TL, SGRL and the survival rate of Nemo fish larvae were the highest (10.01 ± 0.150 mm, 7.20 ± 0.099%/day and 82.67 ± 0.881%, respectively). Lowest TL, SGRL and survival rate were obtained in larvae fed with the control diet (8.65 ± 0.051 mm, 6.23 ± 0.041%/day and 68.70 ± 0.881%, respectively). The results of this experiment suggest that the optimal Selco concentration used to enrich live feeds for Nemo fish larvae is 100 ppm, which can improve the production efficiency of Nemo stock

Investigation of salt-tolerant rhizosphere bacteria from seawater-intruding paddy rice field in Vietnam

Salt‐tolerant plant growth‐promoting rhizobacteria (ST‐PGPR) are known as potential tools to improve rice salinity tolerance. In this study, we aimed to investigate the plant growth‐promoting rhizobacteria community richness of the paddy rice fields in Soc Trang and Ben Tre Provinces where were seriously affected by sea level rise. The salinity in the sampling sites ranged from 0.14‰ to 2.17‰ in November 2018, the rainy season. The microbial abundance of samples was evaluated by spreading the samples in tryptic soy agar (TSA) medium supplemented with various concentrations of NaCl. With the increase of salt concentration up to 10% NaCl, a total number of bacteria decreased for all the samples, ranging from 106 to 104 CFU/g, and bacterial colonies were not observed at 30% NaCl. Among a total of 48 salt-resisting bacteria isolated from the rice paddy field mud surrounding the rice root, 22 isolates were able to produce indole-3-acetic acid (IAA: phytohormone for the plant growth). Seventeen out of 48 isolates were able to grow in the medium without nitrogen or phosphor sources. Six isolates having high IAA producing activity, nitrogen fixation and phosphate solubilization were belonged to Bacillus (DT6, LT16, and LHT8), Halobacillus (DT8), Aeromonas (LHT1), and Klebsiella (LHT7) genera. All the sequences of the strains DT6, DT8, LT16, LHT1, LHT7, and LHT8 were registered in the GeneBank with the accession numbers MK335670, MK335671, MK335672, MK335673, MK335674, and MK335675, respectively.

PRELIMINARY STUDY OF THE ANTIOXIDANT PROPERTIES OF OPHIOCORDYCEPS SOBOLIFERA

The aim of study was to determine preliminary phytochemical analysis and the antioxidant potential of Ophiocordyceps sobolifera. The antioxidant activity of Ophiocordyceps sobolifera was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and total antioxidant activity methods. Phytochemical analyses revealed the presence of steroids, triterpenoids, alkaloids, phenolics, flavoinods, protein, carbohydarte and saponins. The antioxidant activity of the ethanol extracts and water extracts showed high antioxidant activity with the lowest half maximal inhibitory concentration (IC50) values to 0.70 from 0.95mg/mL, realtively. Total antioxidant capacity of the O. sobolifera showed contained from 5.52 ± 0.14 to 12,71 ± 0.23 mg GA/g or from 3.55 ± 0.15 to 7.87 ± .05 μmol AS/g. These data suggest that O. sobolifera is a natural source of antioxidants