150,879 research outputs found
Evolution of the G+C content frontier in the rat cytomegalovirus genome
No full textWithin the 230138 bp of the rat cytomegalovirus (RCMV) genome, the G+C content changes abruptly at position 142644, constituting a G+C content frontier. To the left of this point, overall G+C content is 69.2%, and to the right it is only 47.6%. A region of extremely low G+C content (33.8%) is found in the 5 kb immediately to the right of the frontier, in which there are no predicted coding sequences. To the right of position 147501, the G+C content rises and predicted coding sequences reappear. However, these genes are much shorter (average 848bp, 50% G+C) than those in the left two-thirds of the genome (average 1462bp, 70% G+C). Whole genome alignment of several viruses indicates that the initial ultra-low G+C region appeared in the common ancestor of the genera Cytomegalovirus and Muromegalovirus, and that the lowering of G+C in the right third has been a subsequent process in the lineage leading to RCMV. The left two-thirds of RCMV has stop codon occurrences at 67.5% of their expected level, based on a modified Markov chain model of stop codon distribution, and the corresponding figure for the right third is 78%. Therefore, despite heavy mutation pressure, selective constraint has operated in the right third of the RCMV genome to maintain a degree of gene length unusual for such low G+C sequences
Conformational changes at the carboxyl terminus of G alpha occur during G protein activation
No full textTo understand the dynamics of conformational changes during G protein activation, surface exposed cysteine residues on G alpha were fluorescently labeled. Limited trypsinolysis and mutational analysis of recombinant G alpha(t)/G alpha(il) determined that two cysteines are the major fluorescent labeling sites, Cys(210), located in the switch II region, and Cys(347) at the C terminus. Mutants with serines replacing Cys(210) (Chi6a) and Cy-347 (Chi6b) were single fluorescently labeled with lucifer yellow (LY), while a double mutant (Chi6ab) was no longer labeled. When Chi6b was labeled with LY on Cys(210), AlF4- caused a 220% increase in LY fluorescence, indicating that the fluorescent group at Cys(210) is a reporter of conformational change in the switch II region. Chi6a labeled at Cys(347) also showed an AlF4--dependent increase in LY fluorescence (91%), indicating that G alpha activation leads to a conformational change at the COOH terminus. Preactivation of the protein with AlF4- before labeling led to a decreased incorporation of LY into Cys(347) suggesting that G alpha activation buries Cys347. This COOH-terminal conformational change may provide the structural basis for communication between the GDP-binding site on G alpha and activated receptors, and may contribute to dissociation of activated G alpha subunit from activated receptor
One step preparation of pure tau-MnAl phase with high magnetization using strip casting method
No full textFerromagnetic phase of Mn-Al exhibits great potential in the rare-earth free permanent magnetic materials due to its high magnetocrystalline anisotropy, high magnetization, high Curie temperature and low cost. In this work, the strip casting technique was applied to prepare MnAl magnetic phase. X-ray diffraction and energy dispersive X-ray analyses indicate that the as-prepared Mn54Al46 strip sample consists of pure tau-MnAl magnetic phase. It is found that the composition of Mn54Al46 is suitable to prepare tau-MnAl phase during the strip casting process. The Mn54Al46 strip sample synthesized through the strip casting exhibits a fairly high magnetization of 114 emu/g under a field of 5 T, while the coercivity of iHc = 2.8 kOe, magnetization of M-5T = 63.9 emu/g at room temperature can be obtained for Mn54Al46 powder sample. This preparation method can produce a large amount of tau-phase MnAl alloy and promote mass industrialized production. (C) 2017 Author(s)
On super form factors of half-BPS operators in N=4 super Yang-Mills
No full textOpen Access, (c) The Authors. Article funded by SCOAP3. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited
Assessing Ageing Condition of Mineral Oil-Paper Insulation by Polarization/Depolarization Current
No full textAccurately assessing the ageing status of oil-paper insulation in transformer is essential and important. Polarization and Depolarization Current (PDC) technique is effective in assessing the condition of oil-paper insulation system. Though the PDC behaviour of mineral oil-paper insulation has been widely investigated, there is no report about how to make the quantitative analysis of mineral oil-paper insulation ageing condition by PDC. The PDC characteristics of mineral oil-paper insulation samples were investigated over the ageing period at 110°C. A new method for assessing the ageing condition of mineral oil-paper insulation by calculating the depolarization charge quantity was proposed. Results show that the depolarization charge quantity of mineral oil-paper insulation sample is very sensitive to its ageing condition. The stable depolarization charge quantity could be used to predict the ageing condition of mineral oil-paper insulation
G-quadruplexes: Kinetic stability and effects on the c-KIT promoter
No full textIn addition to the famous Watson & Crick model for B-form duplex DNA, guanine-rich DNA sequences can self-assemble under certain conditions to form a four-stranded structure known as a G-quadruplex. G-quadruplexes are composed of stacks of Gquartets, in which four guanines are arranged in a square planar array, interacting via eight hydrogen bonds. Monovalent cations especially K+ and Na+ but not Li+ stabilize this structure by binding with the central carbonyl O6 atoms. Bioinformatic databases have revealed potential quadruplex-forming sequences throughout the genome and tandem repeats of guanines are found to accumulate upstream of the transcription initiation site of several proto-oncogenes. The promoter region of the c-kit proto-oncogene contains two potential quadruplex forming sequences. The first part of this work focuses on understanding how the c-kit promoter is regulated by potential G-quadruplex forming structures. We have incorporated 165 base pairs of the c-kit promoter region into a luciferase reporter vector and have constructed several mutant variants of this sequence. Determining the level of luciferase expression of these constructed vectors in HeLa and HCT 116 cells have allowed us to elucidate the effect of quadruplex formation on gene expression. Our results reveal that a decrease in gene expression level is observed from the constructed vectors that carry a very stable quadruplex-forming sequence. In genomic DNA, these putative quadruplex-forming G-rich sequences are normally base paired with their complementary C-rich strands to generate duplex DNA. Structural transitions of B-form DNA (duplex) to non-B-form DNA (quadruplex) require local melting, which is facilitated by negative superhelical tension. We have examined in vitro the effect of DNA supercoiling on the reaction of the c-kit promoter (and some variants of the natural sequences) with three chemical probes KMnO4, DEPC, and DMS. The results demonstrated that negative superhelicity did not significantly affect the formation of G-quadruplex. For the first time, we have used two-dimensional agarose gel electrophoresis to probe topology-dependent structural transitions in the c-kit promoter and some of its modified versions. Our results showed that the constructed vectors that carried the very stable quadruplex-forming sequence undergo unusual structural transition. Finally, we have used a gel based assay to understand the dynamic equilibrium between quadruplex and duplex DNA under defined conditions. The results show that at elevated temperatures, the formation of duplex DNA with these G-rich sequences is kinetically reversible and we have measured the rate at which the duplex strand exchanges with single-stranded DNA. The formation of both quadruplex and duplex DNA are cation and concentration-dependent
NOx degradation ability of S-g-C3N4/MgAl-CLDH nanocomposite and its potential application in cement-based materials
No full textIn this study a new photocatalytic nanocomposite, S-g-C3N4/MgAl-CLDH, was synthesized and implemented into cement mortar by internal mixing or coating. The photocatalytic NOx degradation efficiency of the S-g-C3N4/MgAl-CLDH and photocatalytic mortar was investigated. The NOx degradation efficiency and photoluminescence spectra of S-g-C3N4/MgAl-CLDH after being immersed in the simulated concrete pore solution were evaluated to assess its chemical stability. The results show that compared with S-g-C3N4, the S-g-C3N4/MgAl-CLDH exhibits a narrower bandgap (2.45 eV), a lower photogenerated electron-hole pair recombination rate and a higher specific surface area (36.86 m2 g−1). After 21 min of visible light irradiation, the NOx degradation rate of S-g-C3N4/MgAl-CLDH achieves 100% as compared to merely 81.5% of S-g-C3N4. After being submerged in simulated concrete pore solution, the S-g-C3N4/MgAl-CLDH exhibits only a slight decrease of 5% in degradation rate after 12 min of irradiation, confirming a good compatibility and stability in cement-based materials. The NOx degradation ability of the internally mixed mortar is enhanced with an increase in the dosage of S-g-C3N4/MgAl-CLDH. For coated mortar, in contrast, a decline in NOx degradation rate is observed after 5 layers of coating owing to the lower porosity of mortar after excessive coating
Studi Eksperimental Performa Mekanik Spesimen Komposit Laminat Hybrid dan Propeller Drone Quadcopter dengan Susunan C/G/C/G/C/G/C dan G/C/G/C/G/C/G
No full textPerkembangan teknologi terjadi secara pesat seiring dengan bertambahnya waktu, contohnya pada perkembangan teknologi drone atau (UAV) unmanned aerial vehicle. Drone merupakan teknologi yang dapat membantu kehidupan manusia di berbagai sektor seperti media ataupun militer. Namun seiring perkembangan di bidang drone dan komponen-nya yang pesat, penelitian mengenai pembuatan atau manufaktur propeller drone quadcopter dari bahan komposit di Institut Teknologi Sepuluh Nopember masih belum ada berdasarkan hasil pencarian di data repository Institut Teknologi Sepuluh Nopember. Pada penelitian ini kami mempelajari performa mekanik dan menganalisa spesimen komposit laminat dengan susunan carbon fiber, fiberglass, dan hybrid serta propeller drone quadcopter hybrid dengan susunan yang sama dengan spesimen komposit laminat yaitu lapisan susunan C/G/C/G/C/G/C dan G/C/G/C/G/C/G. Pada penelitian ini spesimen komposit laminat dibentuk sesuai dengan standardisasi ISO-179 dan ASTM D3039-17 serta dibuat dengan metode vacuum resin infusion, untuk propeller drone quadcopter dengan metode hand lay-up. Pengujian tensile, pengujian impact, dan pengujian cantilever bending dilakukan untuk mengetahui performa mekanik dari spesimen komposit laminat dan propeller drone quadcopter dengan susunan hybrid. Pada penelitian ini, pengujian tensile dilakukan pertama pada spesimen komposit carbon fiber dan fiberglass, dimana spesimen komposit dengan jenis carbon fiber memiliki rata – rata nilai load, stress, strain, dan modulus young lebih besar dibanding fiberglass. Untuk pengujian tensile dari spesimen variasi lapisan susunan G/C/G/C/G/C/G mempunyai nilai rata – rata yang lebih tinggi untuk load, stress, strain, tetapi mempunyai nilai yang lebih rendah untuk modulus young dibanding spesimen C/G/C/G/C/G/C. Pada pengujian impact spesimen variasi lapisan susunan G/C/G/C/G/C/G mempunyai nilai energi serap dan energi impact yang lebih besar dibanding C/G/C/G/C/G/C. Pengujian cantilever bending dilakukan dengan pengaturan displacement 10mm dan didapatkan hasil spesimen C/G/C/G/C/G/C lebih mampu menahan load lebih tinggi dibanding spesimen G/C/G/C/G/C/G. Pengamatan makroskopis juga dilakukan untuk mengetahui patahan dan kegagalan yang terjadi pada spesimen komposit laminat hybrid yang diuji impact dan tensile. Kegagalan berupa delaminasi dan fiber pull-out yang terjadi pada spesimen tensile mempengaruhi nilai stiffness dan load-drop pada spesimen tensile yang diuji. Sedangkan pada spesimen impact terjadi kegagalan delaminasi dan fiber fracture pada sisi compression dan tension juga mempengaruhi nilai energi serap dari spesimen yang diuji impact.
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Rapid technological advancements have been occurring over time, such as in the development of drone technology, also known as Unmanned Aerial Vehicles (UAVs). Drones are technological innovations that have the potential to assist humans in various sectors, including media and the military. However, despite the rapid progress in the field of drones and their components, there is still a lack of research on the manufacture of quadcopter drone propellers using composite materials at the Sepuluh Nopember Institute of Technology, based on the search results in the institute's data repository. In this study, the researchers focused on investigating the mechanical performance and analyzing composite laminate specimens with different compositions, such as carbon fiber, fiberglass, and hybrid structures, as well as hybrid quadcopter drone propellers with similar arrangements of C/G/C/G/C/G/C and G/C/G/C/G/C/G layers as in the composite laminate specimens. The composite laminate specimens were formed following the ISO-179 and ASTM D3039-17 standards and were made using the vacuum resin infusion method, while the quadcopter drone propellers were made using the hand lay-up method. Various tests were conducted to assess the mechanical performance of the composite laminate specimens and the hybrid quadcopter drone propellers. These tests included tensile testing, impact testing, and cantilever bending testing. Tensile testing was carried out first on the carbon fiber and fiberglass composite specimens. It was observed that the carbon fiber composite specimens had higher average values of load, stress, strain, and young's modulus compared to the fiberglass composite specimens. The G/C/G/C/G/C/G arrangement in the composite laminate specimens showed higher average values for load, stress, and strain but lower values for young's modulus compared to the C/G/C/G/C/G/C arrangement. In impact testing, the G/C/G/C/G/C/G arrangement exhibited higher values for energy absorption and impact energy compared to the C/G/C/G/C/G/C arrangement. Cantilever bending testing was performed with a 10mm displacement setting, and the results showed that the C/G/C/G/C/G/C arrangement was better able to withstand higher loads compared to the G/C/G/C/G/C/G arrangement. Macroscopic observations were also carried out to determine the fractures and failures that occurred in the hybrid composite laminate specimens during impact and tensile testing. Failures such as delamination and fiber pull-out affected the stiffness and load-drop values of the tensile-tested specimens. Additionally, in the impact-tested specimens, delamination and fiber fracture occurred on the compression and tension sides, which also influenced the energy absorption values of the specimens. In conclusion, this research contributes valuable insights into the mechanical properties and performance of composite laminates and hybrid quadcopter drone propellers. The findings could potentially pave the way for further advancements and applications in the field of drone technology, especially concerning the use of composite materials to improve their efficiency and capabilities
Bäcklund transformations for noncommutative anti-self-dual Yang-Mills equations
No full textWe present Bäcklund transformations for the non-commutative anti-self-dual Yang–Mills equations where the gauge group is G = GL(2) and use it to generate a series of exact solutions from a simple seed solution. The solutions generated by this approach are represented in terms of quasi-determinants and belong to a non-commutative version of the Atiyah–Ward ansatz. In the commutative limit, our results coincide with those by Corrigan, Fairlie, Yates and Goddard
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