Fractional Quantum Hall Effect in Suspended Graphene: Transport Coefficients and Electron Interaction Strength

Strongly correlated electron liquids which occur in quantizing magnetic fields reveal a cornucopia of fascinating quantum phenomena such as fractionally charged quasiparticles, anyonic statistics, topological order, and many others. Probing these effects in GaAs-based systems, where electron interactions are relatively weak, requires sub-kelvin temperatures and record-high electron mobilities, rendering some of the most interesting states too fragile and difficult to access. This prompted a quest for new high-mobility systems with stronger electron interactions. Recently, fractional-quantized Hall effect was observed in suspended graphene (SG), a free-standing monolayer of carbon, where it was found to persist up to T=10 K. The best results in those experiments were obtained on micron-size flakes, on which only two-terminal transport measurements could be performed. Here we pose and solve the problem of extracting transport coefficients of a fractional quantum Hall state from the two-terminal conductance. We develop a method, based on the conformal invariance of two-dimensional magnetotransport, and illustrate its use by analyzing the measurements on SG. From the temperature dependence of longitudinal conductivity, extracted from the measured two-terminal conductance, we estimate the energy gap of quasiparticle excitations in the fractional-quantized nu=1/3 state. The gap is found to be significantly larger than in GaAs-based structures, signaling much stronger electron interactions in suspended graphene. Our approach provides a new tool for the studies of quantum transport in suspended graphene and other nanoscale systems

Microscopy of glazed layers formed during high temperature sliding wear at 750C

The evolution of microstructures in the glazed layer formed during high temperature sliding wear of Nimonic 80A against Stellite 6 at 750 ◦C using a speed of 0.314ms−1 under a load of 7N has been investigated using scanning electron microscopy (SEM), energy dispersive analysis by X-ray (EDX), X-ray diffraction (XRD) analysis, scanning tunnelling microscopy (STM) and transmission electron microscopy (TEM). The results indicate the formation of a wear resistant nano-structured glazed layer. The mechanisms responsible for the formation of the nano-polycrystalline glazed layer are discussed

On the Approximability and Hardness of the Minimum Connected Dominating Set with Routing Cost Constraint

In the problem of minimum connected dominating set with routing cost constraint, we are given a graph $G=(V,E)$, and the goal is to find the smallest connected dominating set $D$ of $G$ such that, for any two non-adjacent vertices $u$ and $v$ in $G$, the number of internal nodes on the shortest path between $u$ and $v$ in the subgraph of $G$ induced by $D \cup \{u,v\}$ is at most $\alpha$ times that in $G$. For general graphs, the only known previous approximability result is an $O(\log n)$-approximation algorithm ($n=|V|$) for $\alpha = 1$ by Ding et al. For any constant $\alpha > 1$, we give an $O(n^{1-\frac{1}{\alpha}}(\log n)^{\frac{1}{\alpha}})$-approximation algorithm. When $\alpha \geq 5$, we give an $O(\sqrt{n}\log n)$-approximation algorithm. Finally, we prove that, when $\alpha =2$, unless $NP \subseteq DTIME(n^{poly\log n})$, for any constant $\epsilon > 0$, the problem admits no polynomial-time $2^{\log^{1-\epsilon}n}$-approximation algorithm, improving upon the $\Omega(\log n)$ bound by Du et al. (albeit under a stronger hardness assumption)

Fast Witness Extraction Using a Decision Oracle

The gist of many (NP-)hard combinatorial problems is to decide whether a universe of $n$ elements contains a witness consisting of $k$ elements that match some prescribed pattern. For some of these problems there are known advanced algebra-based FPT algorithms which solve the decision problem but do not return the witness. We investigate techniques for turning such a YES/NO-decision oracle into an algorithm for extracting a single witness, with an objective to obtain practical scalability for large values of $n$. By relying on techniques from combinatorial group testing, we demonstrate that a witness may be extracted with $O(k\log n)$ queries to either a deterministic or a randomized set inclusion oracle with one-sided probability of error. Furthermore, we demonstrate through implementation and experiments that the algebra-based FPT algorithms are practical, in particular in the setting of the $k$-path problem. Also discussed are engineering issues such as optimizing finite field arithmetic.Comment: Journal version, 16 pages. Extended abstract presented at ESA'1

Conceptualising neuroscience-based leadership behaviour

This thesis primarily focuses on conceptualising Neuroscience Based Leadership (NSBL) by providing a working definition of NSBL, describing the foundational concepts and core behaviours of neuroscience-based leadership (NSBL), and presenting a conceptual framework that integrates interdisciplinary perspectives on leadership behaviour. This was achieved by: 1. Reviewing existing relevant scientific literature and highlighting current knowledge gaps in the conceptualisations of NSBL using Leadership Behaviour, Social Cognitive Neuroscience (SCN), and Neuropsychotherapy (NP) 2. Conducting a small-scale research project using semi-structured, in-depth interviews with three neuroscientists who have employed neuroscience-based diagnostics in leadership development within a corporate context. This study’s key findings reveal key conceptual themes with the following theoretical propositions that underpin NSBL key behaviours: social safety is a primary operating principle; conscious thinking and nonconscious processes drive behaviour; nature-nurture dynamics influence behaviour; experienced-based neuroplasticity drives change; and overlapping large-scale brain networks enable information processing in the brain. 3. Designing and implementing a qualitative Delphi study involving 33 experienced professionals in NSBL to explore how NSBL is defined, conceptualise NSBL as a different domain of leadership behaviour, and provide descriptors of NSBL key behaviours 4. Adopting a case study approach involving an organisational psychologist experienced in Neuropsychotherapy and drawing on his views and experiences to produce a single-case study of NSBL within the context of organisational psychology and applied organisational neuroscience (AONS). 5. Undertaking a reflective and critical review of the four pieces of research and proposing a theoretical framework of NSBL, specifically within formal organisations, to inform, support, foster and develop future NSBL-based behaviour. The contribution of this study is broad in that it offers a working definition of neuroscience-based leadership and an interdisciplinary conceptual framework to guide practitioners and further research. This conceptual framework integrates theoretical propositions regarding leadership behaviour from Leadership Behaviour theory, Social Cognitive and Affective Neuroscience, and Neuropsychotherapy. The theoretical framework of NSBL addresses gaps in the literature by differentiating four domains of NSBL: stress resilience-focused core behaviours, affect and emotional-focused core behaviours, relationship-focused core behaviours, and task-focused core behaviours. It also provides neuroscientific concepts that underpin behaviour. The contribution to practice is that this study advances the understanding of how formal organisations can apply a neuroscientific lens to inform the design of leadership development interventions. This integrative, interdisciplinary theoretical framework can be used for leadership coaching at an individual level. At the group level, it can facilitate team building. It can provide a neuroscientific language for mental experience at an organisational level, thereby enhancing the explanatory power of concepts in leadership and organisational behaviour

Microwave photoresistance of a high-mobility two-dimensional electron gas in a triangular antidot lattice

The microwave (MW) photoresistance has been measured on a high-mobility two-dimensional electron gas patterned with a shallow triangular antidot lattice, where both the MW-induced resistance oscillations (MIRO) and magnetoplasmon (MP) resonance are observed superposing on sharp commensurate geometrical resonance (GR). Analysis shows that the MIRO, MP, and GR are decoupled from each other in these experiments.Comment: 5 pages, 4 figures, paper accepted by PR

Mangiferin: A Promising Anticancer Bioactive

Of late, several biologically active antioxidants from natural products have been investigated by the researchers in order to combat the root cause of carcinogenesis, i.e., oxidative stress. Mangiferin, a therapeutically active C-glucosylated xanthone, is extracted from pulp, peel, seed, bark and leaf of Mangifera indica. These polyphenols of mangiferin exhibit antioxidant properties and tend to decrease the oxygen-free radicals, thereby reducing the DNA damage. Indeed, its capability to modulate several key inflammatory pathways undoubtedly helps in stalling the progression of carcinogenesis. The current review article emphasizes an updated account on the patents published on the chemopreventive action of Mangiferin, apoptosis induction made on various cancer cells, along with proposed antioxidative activities and patent mapping of other important therapeutic properties. Considering it as promising polyphenol, this paper would also summarize the diverse molecular targets of Mangiferin