50175 research outputs found
Sort by
Topological insulator n-p-n junctions in a magnetic field
No full textElectrical transport in three dimensional topological insulators (TIs) occurs through spin-momentum locked topological surface states that enclose an insulating bulk. In the presence of a magnetic field, surface states get quantized into Landau levels giving rise to chiral edge states that are naturally spin-polarized due to spin momentum locking. It has been proposed that p-n junctions of TIs exposed to external magnetic fields can manifest unique spin dependent effects, apart from forming basic building blocks for highly functional spintronic devices. Here, for the first time we study electrostatically defined n-p-n junctions of dual-gated devices of the three dimensional topological insulator BiSbTe 1.25 Se 1.75 in the presence of a strong magnetic field, revealing striking signatures of suppressed or enhanced electrical transport depending upon the chirality of quantum Hall edge states created at the n-p and p-n junction interfaces. Theoretical modeling combining the electrostatics of the dual gated TI n-p-n junction with the Landauer Buttiker formalism for transport through a network of chiral edge states explains our experimental data. Our work not only opens up a route towards exotic spintronic devices but also provides a test bed for investigating the unique signatures of quantum Hall effects in topological insulators. © The Royal Society of Chemistry
2D-MoS2 photocatalyzed cross dehydrogenative coupling reaction synchronized with hydrogen evolution reaction
No full textThe chemically exfoliated 2D-MoS2 has a mixture of 1T (metallic) and 2H (semiconducting) phases. It has shown a considerably good catalytic activity for hydrogen evolution reaction (HER), proceeding via electrochemical as well as photochemical pathways. Experimentalists have utilized triethanolamine or other sacrificial donors along with Eosin Y as a photosensitizer. But the potential of this reaction has not yet been fully explored as the sacrificial donor is wasted in the oxidation process. The oxidation cycle of this process can be used in many organic transformation(s). Herein, we report the use of the oxidative cycle for efficient cross dehydrogenative coupling (CDC) reaction with tetrahydroisoquinoline and indole substrates as well as their derivatives, parallel to HER. The reaction results in good to excellent yield of the corresponding product under visible light irradiation at room temperature. The mechanistic investigation has also been carried out. This study is a potential example of how to fully harness the oxidation and reduction cycles of many semiconductor based photocatalysts
Three-stage phase separation kinetics in a model liquid binary mixture: A computational study
No full textWe study microscopic aspects of initial phase separation through atomistic molecular dynamics simulation of a structure breaking liquid binary mixture. We find that the phase separation kinetics in a fluid binary mixture model system can indeed be unusual. It can be fast, with a crossover from a pronounced exponential to non-exponential and non-linear dynamics. An important outcome of this work is the quantification of time scales involved in phase separation kinetics at an early stage. The initial exponential phase separation is complete within similar to 100 ps. The initial phase separation involves aggregation of small droplets that form rapidly after the quench. This is followed by segregation that gives rise to pattern formation with multiple bands of segregated species. During this initial phase, a particle is found to have moved only about similar to 5 molecular diameters. The next stage is slower and characterized by break-up and disappearance of small islands of species trapped inside the domains of other species of the binary mixture. The phase separation in this second stage is highly non-exponential and power-law-like. We identify a new feature in the very late stage of phase separation kinetics that seems to have eluded previous attention, the smoothing of the rugged interface between the two species. This is opposite to the roughening transition one finds on the surface of solids in contact with its vapor phase. The present atomistic simulation provides a molecular picture in terms of molecular motions and displacements
Physical and functional interaction between nucleoid-associated proteins HU and Lsr2 of Mycobacterium tuberculosis: altered DNA binding and gene regulation
No full textNucleoid-associated proteins (NAPs) in bacteria contribute to key activities such as DNA compaction, chromosome organization and regulation of gene expression. HU and Lsr2 are two principal NAPs in Mycobacterium tuberculosis (Mtb). HU is essential for Mtb survival and is one of the most abundant NAPs. It differs from other eubacterial HU proteins in having a long, flexible lysine- and arginine-rich carboxy-terminal domain. Lsr2 of Mtb is the functional analogue of the bacterial NAP commonly called H-NS. Lsr2 binds to and regulates expression of A/T-rich portions of the otherwise G/C-rich mycobacterial chromosome. Here, we demonstrate that HU and Lsr2 interact to form a complex. The interaction occurs primarily through the flexible carboxy-terminal domain of HU and the acidic amino-terminal domain of Lsr2. The resulting complex, upon binding to DNA, forms thick nucleoprotein rods, in contrast to the DNA bridging seen with Lsr2 and the DNA compaction seen with HU. Furthermore, transcription assays indicate that the HU-Lsr2 complex is a regulator of gene expression. This physical and functional interaction between two NAPs, which has not been reported previously, is likely to be important for DNA organization and gene expression in Mtb and perhaps other bacterial species
Regulation of meristem maintenance and organ identity during rice reproductive development
No full textWe review developmental transitions of rice shoot meristems to branched inflorescences with floral meristems, highlighting evolutionarily conserved regulators and factors with distinct functions in shoot architecture and reproductive development. Abstract Grasses have evolved complex inflorescences, where the primary unit is the specialized short branch called a spikelet. Detailed studies of the cumulative action of the genetic regulators that direct the progressive change in axillary meristem identity and their terminal differentiation are crucial to understanding the complexities of the inflorescence and the development of a determinate floret. Grass florets also pose interesting questions concerning the morphologies and functions of organs as compared to other monocots and eudicots. In this review, we summarize our current knowledge of the regulation of the transitions that occur in grass inflorescence meristems, and of the specification of floret meristems and their determinate development. We primarily use rice as a model, with appropriate comparisons to other crop models and to the extensively studied eudicot Arabidopsis. The role of MADS-domain transcription factors in floral organ patterning is well documented in many eudicots and in grasses. However, there is evidence to suggest that some of these rice floral regulators have evolved distinctive functions and that other grass species-specific factors and regulatory pathways occur - for example the LOFSEP E' class genes OsMADS1 and OsMAD34, and ramosa genes. A better understanding of these systems and the epigenetic regulators and hormone signaling pathways that interact with them will provide new insights into the rice inflorescence meristem and the differentiation of its floret organs, and should indicate genetic tools that can be used to control yield-related traits in both rice and other cereal crops
Search for Narrow Hγ Resonances in Proton-Proton Collisions at ffiffis p = 13 TeV
No full textA search for heavy, narrow resonances decaying to a Higgs boson and a photon (Hγ) has been performed in proton proton collision data at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb-1 collected with the CMS detector at the LHC in 2016. Events containing a photon and a Lorentz-boosted hadroni -cally decaying Higgs boson reconstructed as a single, large-radius jet are considered, and the γ+jet invariant mass spectrum is analyzed for the presence of narrow resonances. To increase the sensitivity of the search, events are categorized depending on whether or not the large-radius jet can be identified as a result of the merging of two jets originating from b quarks. Results in both categories are found to agree with the predictions of the standard model. Upper limits on the production rate of Hγ resonances are set as a function of their mass in the range of 720-3250 GeV, representing the most stringent constraints to date. © 2019 CERN for the CMS Collaboration.Published by the American Physical Society
HOLOMORPHIC MOTIONS AND COMPLEX GEOMETRY
No full textWe show that the graph of a holomorphic motion of the unit disc cannot be biholomorphic to a strongly pseudoconvex domain in C-n
Dictionary Alignment With Re-Ranking for Low-Resolution NIR-VIS Face Recognition
No full textRecently, near-infrared (NIR) images are increasingly being captured for recognizing faces in low-light/nighttime conditions. Matching these images against the controlled high-resolution visible facial images usually present in the database is a challenging task. In surveillance scenarios, the NIR images can have very low resolution and also non-frontal pose which makes the problem even more challenging. In this paper, we propose an orthogonal dictionary alignment approach for addressing this problem. We also propose a re-ranking approach to further improve the recognition performance for each probe by combining the rank list given by the proposed algorithm with that given by another complementary feature/algorithm. Finally, we have also collected our own database Heterogeneous face recognition across Pose and Resolution (HPR) that has facial images captured from two surveillance quality NIR cameras and one high-resolution visible camera, with significant variations in head pose and resolution. Extensive experiments on the modified CASIA NIR-VIS 2.0 database, the Surveillance Camera face database, and our HPR database show the effectiveness of the proposed approaches and the collected database
Analytical Evaluation and Reduction of Torque Harmonics in Induction Motor Drives Operated at Low Pulse Numbers
No full textInduction motor drives operated with a low ratio of the switching frequency to the fundamental frequency (i.e., pulse number) are prone to have high magnitudes of low-order torque harmonics. This paper proposes a method to analytically evaluate the harmonic torque spectrum based on the pulsewidth-modulated voltage waveforms for low pulse number operation. The predicted torque harmonic spectra for different pulsewidth-modulated waveforms are validated through simulations and experiments. This paper also reports optimal switching angles to minimize the total rms value of torque harmonics of order 6, 12, 18, . . . , 6(N - 1), considering the number of switching angles per quarter (N) to be 4 and 5. Compared to sine triangle pulsewidth modulation and selective harmonic elimination pulsewidth modulation with the same pulse number, the proposed optimal switching angles significantly reduce the total rms value of all harmonic torques of order lower than 6N. Extensive simulation and experimental results on a 3.7-kW induction motor drive are presented to demonstrate the superior performance of the proposed optimal pulsewidth modulation
Understanding the role of oxo and peroxido species in the glutathione peroxidase (GPx)-like activity of metal based nanozymes
No full textNanomaterials having enzyme-like activities (nanozymes) attract significant attention. Particularly, metal-based nanozymes that exhibit superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activities find applications in controlling the redox state of the cells. It has been shown that V2O5 functionally mimic the GPx enzyme by catalytically reducing H2O2 in the presence of glutathione (GSH). In this paper, we discuss the role of oxo and peroxido species in the GPx activity of V2O5 and MoO3. A detailed mechanistic study reveals that the GPx activity of these materials depends on the reactivity of oxo moiety on the surface of the material with H(2)O(2 )to form the peroxido linkages