840 research outputs found
Molecular Phylogeny of OVOL Genes Illustrates a Conserved C2H2 Zinc Finger Domain Coupled by Hypervariable Unstructured Regions
No full textOVO-like proteins (OVOL) are members of the zinc finger protein family and serve as transcription factors to regulate gene expression in various differentiation processes. Recent studies have shown that OVOL genes are involved in epithelial development and differentiation in a wide variety of organisms; yet there is a lack of comprehensive studies that describe OVOL proteins from an evolutionary perspective. Using comparative genomic analysis, we traced three different OVOL genes (OVOL1-3) in vertebrates. One gene, OVOL3, was duplicated during a whole-genome-duplication event in fish, but only the copy (OVOL3b) was retained. From early-branching metazoa to humans, we found that a core domain, comprising a tetrad of C2H2 zinc fingers, is conserved. By domain comparison of the OVOL proteins, we found that they evolved in different metazoan lineages by attaching intrinsically-disordered (ID) segments of N/C-terminal extensions of 100 to 1000 amino acids to this conserved core. These ID regions originated independently across different animal lineages giving rise to different types of OVOL genes over the course of metazoan evolution. We illustrated the molecular evolution of metazoan OVOL genes over a period of 700 million years (MY). This study both extends our current understanding of the structure/function relationship of metazoan OVOL genes, and assembles a good platform for further characterization of OVOL genes from diverged organisms
Arbitration and Dispute Settlement in Foreign Indirect Investment. The increasing significance and use of arbitration in international loan agreements, syndicated loans and international bond issues
No full textThis dissertation examines the suitability of arbitration for the resolution of securities regulatory claims and it adoption globally, which has resulted in international arbitration becoming the favoured dispute resolution mechanism in the securities industry. The author explains that disputes arising out of international bilateral and syndicated loan agreements are generally considered to be arbitrable, while international bond disputes are often derived from the controversies over the application of mandatory national laws and the compliance with securities regulation provisions - so the arbitrability of international bond disputes depends on the acceptance of the arbitrability of securities regulatory claims
A monolithically integrated power JFET and Junction Barrier Schottky diode in 4H silicon carbide
No full textEfficiency of power management circuits depends significantly on their constituent switches and rectifiers. The demands of technology are increasingly running up against the intrinsic properties of Si based power devices. 4H-Silicon Carbide (SiC) has superior properties that make it attractive for high power applications. SiC rectifiers are already a competitive choice and SiC switches have also been commercialized recently. Junction Barrier Schottky (JBS) diodes, which combine the advantages of PN and Schottky, have higher Figure of Merit (FOM) as rectifiers. Among switches, a robust and mature process has been developed for Silicon Carbide Vertical Junction Field Effect Transistors (VJFETs), which currently gives it the highest unipolar FOM. Switches are frequently combined with anti-parallel diodes in power circuits. This thesis describes the development of a SiC-based monolithically integrated power switch and diode. Monolithic integration increases reliability and efficiency, and reduces cost. Because of their superior properties and similarities in fabrication, we chose the SiC VJFET and JBS diode as the switch and rectifier. Detailed design, fabrication and characterization of the integrated switch to block above 800 V and conduct current beyond 100 A/cm2 is explained. In this process, the first physics-based 2-D compact model is developed for reverse leakage in a JBS diode as a function of design parameters. Since the gate-channel junctions of SiC VJFETs cannot be assumed to be abrupt, an existing analytical model for Si VJFETs is extended to account for graded gate-channel junctions. Using these analytical models, design rules are developed for the VJFET and JBS diode. Finite element simulations are used to find the best anode layout of the JBS diode and optimize electric field termination in the integrated device to ensure their capability to operate at high voltage. Finally, a spin-on glass based process is developed for filling the gate trenches of the VJFET to improve long-term robustness in extreme environments. The integrated power switch developed in this thesis points to the attractions of monolithic integration in SiC power circuits. Analytical compact design equations derived here will facilitate faster and easier design of switches and rectifiers for desired circuit operation.Ph. D.Includes bibliographical referencesIncludes vitaby Rahul Radhakrishna
Load Balancing in Wireless Mobile Ad Hoc Networks
No full textAd hoc networks are made up of groups of similar nodes, such as computers or embedded devices. Each node works on its own and talks to the others through a wireless channel. Networks like these are made up of groups of nodes that are either next to each other or connected by another wireless node. Nodes are grouped together along their wireless links to make clusters. Nodes that can talk to other nodes in their transmission range are called cluster heads. This can use cluster heads to send packets to the right nodes in your cluster. In an Ad Hoc network, the idea behind it is that nodes don\u27t always move in the same way. Cluster Heads are picked by different algorithms in different ways. Some of these rules make it clear that some nodes are more important than others. Because of the extra work and faster energy loss that could happen because of more contacts, these nodes may be taken out of the network. Load-balancing across Cluster Heads is necessary to make sure that every node has a fair chance to be a Cluster Head. We Proposed that a number of changes should be made to current algorithms in order to fix the uneven spread of nodes among Cluster Heads and make nodes in a network that uses the fuzzy algorithm last longer.Load balancing in Wireless Mobile Ad Hoc Networks (MANETs) ensures equitable distribution of network traffic among nodes and resources. Due to the ongoing mobility and dynamic nature of nodes in MANETs, this aspect holds significant importance
Chiral superconductivity from repulsive interactions in doped graphene
No full textAuthor Manuscript 17 Sep 2011Chiral superconductivity, which breaks time-reversal symmetry, can exhibit a wealth of fascinating properties that are highly sought after for nanoscience applications. We identify doped graphene monolayer as a system where chiral superconductivity can be realized. In this material, a unique situation arises at a doping where the Fermi surface is nested and the density of states is singular. In this regime, d-wave superconductivity can emerge from repulsive electron–electron interactions. Using a renormalization group method, we argue that superconductivity dominates over all competing orders for generic weak repulsive interactions. Superconductivity develops simultaneously in two degenerate d-wave pairing channels. We argue that the resulting superconducting state is of chiral type, with the phase of the superconducting order parameter winding by 4π around the Fermi surface. Realization of this state in doped graphene will prove that superconductivity can emerge from electron–electron repulsion, and will open the door to applications of chiral superconductivity
Adding diversity and realism to LAVA, a vulnerability addition system
No full textThesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 63-64).In this thesis, I designed and implemented several modifications to LAVA, a vulnerability addition system, with the goal of improving realism and diversity of the injected bugs. Specifically, I describe three separate improvements: a method to add fake bugs alongside real ones in order to decrease bug discoverability, two approaches to increase the complexity of the data flow of the inserted bugs, and a standalone program that uses equality saturation to diversify C-source codebases that can be added as a final stage to LAVA. Finally, I present two instances of bug-finding competitions-AutoCTF and Rode0day-that I helped design and run, which leveraged LAVA and the augmentations described in this thesis in order to accomplish their respective goals.by Rahul Sridhar.M. Eng
Spliceosomal Intron Insertions in Genome Compacted Ray-Finned Fishes as Evident from Phylogeny of MC Receptors, Also Supported by a Few Other GPCRs
No full textBackground: Insertions of spliceosomal introns are very rare events during evolution of vertebrates and the mechanisms governing creation of novel intron(s) remain obscure. Largely, gene structures of melanocortin (MC) receptors are characterized by intron-less architecture. However, recently a few exceptions have been reported in some fishes. This warrants a systematic survey of MC receptors for understanding intron insertion events during vertebrate evolution. Methodology/Principal Findings: We have compiled an extended list of MC receptors from different vertebrate genomes with variations in fishes. Notably, the closely linked MC2Rs and MC5Rs from a group of ray-finned fishes have three and one intron insertion(s), respectively, with conserved positions and intron phase. In both genes, one novel insertion was in the highly conserved DRY motif at the end of helix TM3. Further, the proto-splice site MAG up arrow R is maintained at intron insertion sites in these two genes. However, the orthologs of these receptors from zebrafish and tetrapods are intron-less, suggesting these introns are simultaneously created in selected fishes. Surprisingly, these novel introns are traceable only in four fish genomes. We found that these fish genomes are severely compacted after the separation from zebrafish. Furthermore, we also report novel intron insertions in P2Y receptors and in CHRM3. Finally, we report ultrasmall introns in MC2R genes from selected fishes. Conclusions/Significance: The current repository of MC receptors illustrates that fishes have no MC3R ortholog. MC2R, MC5R, P2Y receptors and CHRM3 have novel intron insertions only in ray-finned fishes that underwent genome compaction. These receptors share one intron at an identical position suggestive of being inserted contemporaneously. In addition to repetitive elements, genome compaction is now believed to be a new hallmark that promotes intron insertions, as it requires rapid DNA breakage and subsequent repair processes to gain back normal functionality
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