Physics

<p>Shiv Nadar University is a comprehensive, multidisciplinary, research-focused, and student-centric University offering a full range of academic programs at the undergraduate, postgraduate and doctoral level. With state-of-the-art infrastructure, the University comprises of academic wings, sophisticated labs, international standard sports facilities, amphitheaters, auditorium, conference rooms and smart classrooms. The University&rsquo;s goal is to become internationally recognized for the quality of its research and creative endeavors and their applicability to improving quality of life, generating new insights and expanding the boundaries of human knowledge creativity. Committed to excellence in teaching, research and service, the University aims to serve the higher education needs of India and the world beyond.</p>

Shiv Nadar University

Safe and high-capacity cathode materials are a long quest for commercial lithium-ion battery development. Among various searched cathode materials, Li2FeSiO4 has taken the attention due to optimal working voltage, high elemental abundance, and low toxicity. However, as per our understanding and observation, the electrochemical performance of this material is significantly limited by the intrinsic low electronic conductivity and slow lithium-ion diffusion, which limits the practical capacity (a theoretical value of ∼330 mAh g-1). In this report, using first-principles density functional theory based approach, we demonstrate that chlorine doping on oxygen site can enhance the electronic conductivity of the electrode and concurrently improve the electrochemical performance. Experimentally, X-ray diffraction, X-ray photoelectron spectroscopy, and field-emission gun scanning electron microscopy elemental mapping confirms Cl doping in Li2-xFeSiO4-xClx/C (x ≤ 0.1), while electrochemical cycling performance demonstrated improved performance. The theoretical and experimental studies collectively predict that, via Cl doping, the lithium deinsertion voltage associated with the Fe2+/Fe3+ and Fe3+/Fe4+ redox couples can be reduced and electronic conductivity can be enhanced, which opens up the possibility of utilization of silicate-based cathode with carbonate-based commercial electrolyte. In view of potential and electronic conductivity benefits, our results indicate that Cl doping can be a promising low-cost method to improve the electrochemical performance of silicate-based cathode materials. © 2017 American Chemical Society.

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(SoNS) School of Natural Sciences

ACS Applied Materials and Interfaces

Impact of Cl Doping on Electrochemical Performance in Orthosilicate (Li2FeSiO4): A Density Functional Theory Supported Experimental Approach

Microwave plasma treatment of single wall carbon nanotube (SWNT) films called bucky papers (BPs) resulted in changes in the relative proportion of different chiralities of SWNTs present in the BP and the production of vertical microstructures on the surface of BP. The plasma was created using H2 gas mixed with Ar or CH4, at a temperature of 900 °C and a pressure of 70 Torr. Radial breathing mode spectra of the BPs revealed that the preferential sputtering by plasma is not with respect to the diameter or the metallic nature of SWNTs. We propose that the lengths of SWNTs influence how they interact with plasma. Longer tubes will have higher dielectric constants and hence will be polarized more strongly by the electric field of the plasma sheath. This in turn results in greater ion bombardment and sputtering. Finite element method was used to find the strengths of the induced electric fields on model SWNT surfaces. Microscopy, Raman, and X-ray photoelectron spectroscopy were used to study the effect of plasma on the crystallinity of the surviving SWNTs. Structural integrity of SWNTs was preserved after the plasma treatment. © 2017 Author(s).

Fulltext

Journal of Applied Physics

Structural and compositional changes in single wall carbon nanotube ensemble upon exposure to microwave plasma

We study the CP-violating phase of the quark sector on T2/ZN (N = 2, 3, 4, 6) with non-vanishing magnetic fluxes, where properties of possible origins of the CP violation are investigated minutely. In this system, a non-vanishing value is mandatory in the real part of the complex modulus parameter τ of the two-dimensional torus in order to explain the CP violation in the quark sector. On T2 without orbifolding, underlying discrete flavor symmetries severely restrict the form of Yukawa couplings and it is very difficult to reproduce the observed pattern in the quark sector including the CP-violating phase δCP. When multiple Higgs doublets emerge on T2/Z2, the mass matrices of the zero-mode fermions can be written in the Gaussian textures by choosing appropriate configurations of vacuum expectation values of the Higgs fields. When such Gaussian textures of mass matrices are realized, we show that all of the quark profiles, which are mass hierarchies among the quarks, quark mixing angles, and δCP can be simultaneously realized. © 2017, The Author(s).

Journal of High Energy Physics

CP-violating phase on magnetized toroidal orbifolds

We study a class of models in which the Higgs pair production is enhanced at hadron colliders by an extra neutral scalar. The scalar particle is produced by the gluon fusion via a loop of new colored particles, and decays into di-Higgs through its mixing with the Standard Model Higgs. Such a colored particle can be the top/bottom partner, such as in the dilaton model, or a colored scalar which can be triplet, sextet, octet, etc., called leptoquark, diquark, coloron, etc., respectively. We examine the experimental constraints from the latest Large Hadron Collider (LHC) data, and discuss the future prospects of the LHC and the Future Circular Collider up to 100 TeV. We also point out that the 2.4σ excess in the bb¯ γγ final state reported by the ATLAS experiment can be interpreted as the resonance of the neutral scalar at 300 GeV. © 2017, The Author(s).

European Physical Journal C

Di-Higgs enhancement by neutral scalar as probe of new colored sector

We investigate a 6D Dirac fermion on a rectangle. It is found that the 4D spectrum is governed by N = 2 supersymmetric quantum mechanics. Then we demonstrate that the supersymmetry is very useful for classifying all the allowed boundary conditions and to expand the 6D Dirac field in Kaluza-Klein modes. A striking feature of the model is that even though the 6D Dirac fermion has non-vanishing bulk mass, the 4D mass spectrum can contain degenerate massless chiral fermions, which may provide a hint to solve the problem of the generation of quarks and leptons. It is pointed out that zero-energy solutions are not affected by the presence of the boundaries, while the boundary conditions work well for determining the positive-energy solutions. We also provide a brief discussion on possible boundary conditions in the general case, especially those on polygons. © The Author(s) 2017.

Progress of Theoretical and Experimental Physics

Supersymmetry in the 6D Dirac action

We propose an exact calculation of the probability density function (PDF) and cumulative distribution function (CDF) of mutual information (MI) for a two-user multiple-input multiple-output (MIMO) multiple access channel (MAC) network over block Rayleigh fading channels. This scenario can be found in the uplink channel of MIMO non-orthogonal multiple access (NOMA) system, a promising multiple access technique for 5G networks. So far, the PDF and CDF have been numerically evaluated since MI depends on the quotient of two Wishart matrices, and no closed form for this quotient was available. We derive exact results for the PDF and CDF of extreme (the smallest/the largest) eigenvalues. Based on the results of quotient ensemble, the exact calculation for PDF and CDF of mutual information is presented via Laplace transform approach and by direct integration of joint PDF of quotient ensemble’s eigenvalues. Furthermore, our derivations also provide the parameters to apply the Gaussian approximation method, which is comparatively easier to implement. We show that approximation matches the exact results remarkably well for outage probability, i.e., CDF, above 10\%. However, the approximation could also be used for 1\% outage probability with a relatively small error. We apply the derived expressions to investigate the effects of adding antennas in the receiver and its ability to decode the weak user signal. By supposing no channel knowledge at transmitters and successive decoding at receiver, the capacity of the weak user increases and its outage probability decreases with the increment of extra antennas at the receiver end. © 2017, The Author(s).

Eurasip Journal on Wireless Communications and Networking

On the Exact Distribution of Mutual Information of Two-User MIMO MAC Based on Quotient Distribution of Wishart Matrices

Volume estimates of metric balls in manifolds find diverse applications in various applied sciences including information theory and coding theory. In this paper, the focus is on the exact volume of metric balls in real Grassmann manifold, extending recent results of the complex case. Firstly, we formulate the exact volume as a multi-dimensional integral, which is then represented as an inverse Laplace transform of a Pfaffian. The Pfaffian structure arises as a result of the de-Bruijn formula for multi-dimensional integrals. Using the exact representation, examples of explicit volume formulas are given. As an application, we study the performance bound of the worst-case coherence of Grassmannian frames. © 2016 IEICE.

Proceedings of 2016 International Symposium on Information Theory and Its Applications, ISITA 2016

Volume of metric balls in real Grassmann manifold with an application to frames

In this research paper, in total 212 individual leakage-free Polymethylmethacrylate (PMMA) microfluidic devices are fabricated by maskless lithography, hot embossing lithography and direct bonding technique. The effect of channel aspect ratio on dyed water flow is investigated using these microfluidic devices. Experimental studies show that the dyed water flow is faster on the surface of higher wettability. The effect of capillary pressure on dyed water flow is studied in the fabricated PMMA microfluidic devices. According to the experimental observations, the centrifugal force has prominent effect on the dyed water flow. Also, the effect of bend angle is investigated on the surface-driven capillary flow of water. The polystyrene microparticles have been separated in the microfluidic lab-on-a-chip systems using the investigated flow features. A 100\% separation efficiency is achieved in these lab-on-a-chip systems. These microfluidic lab-on-a-chip systems can be used to separate blood cells from human whole blood for further clinical tests. These experimental studies are important in bioengineering applications. The effect of bend angle as channel geometry to control the surface-driven capillary flow is investigated as a novel approach to control the separation time in microfluidic lab-on-a-chip systems. Also, the effect of surface wettability as surface property to control the surface-driven capillary flow is investigated as a novel approach to control the separation time in microfluidic lab-on-a-chip systems. © 2017 World Scientific Publishing Company.

Surface Review and Letters

Effects of surface properties on fluid engineering generated by the surface-driven capillary flow of water in Microfluidic Lab-On-A-Chip systems for bioengineering applications

One-dimensional diamond nanorods (DNRs) were fabricated from nanocrystalline diamond films using a facile combination of microwave plasma enhanced chemical vapor deposition and reactive ion etching (RIE) techniques. Structural and electrochemical properties of undoped and nitrogen doped DNRs were thoroughly investigated. A cyclic voltammetry study revealed the increase in density of charge carriers when doped with nitrogen. Mott Schottky analysis was implemented for the quantitative determination of the flat band potential, effective density of charge carriers and energy band diagram, which revealed that the undoped sample exhibit p-type behavior, whereas the nitrogen doped sample showed n-type behavior. Defect related damage due to graphitization and hydrogen termination in the undoped DNRs (during RIE) was correlated with the p-type conductivity. Nitrogen doping induces n-type conductivity and enhances effective density of charge carriers. © 2017 Elsevier Ltd

Electrochimica Acta

Probing the flat band potential and effective electronic carrier density in vertically aligned nitrogen doped diamond nanorods via electrochemical method

<p>A new analytical approximate expression for K distribution is proposed by expanding it in terms of orthogonal associated Laguerre polynomial. The expansion is truncated after first three terms, which yields a fairly close approximation to K distribution. The advantage of the proposed approximation is that the analytical closed form expression for bit error rate can be easily derived. KL measure is used to show the accuracy of the proposed approximation. The proposed approximate probability density function and bit error rate work well within the desired range of the channel parameter α, which is 1 &lt; α &lt; 2 and corresponds to the scintillation index value ranging from 2 to 3. We have also demonstrated the utility of our approximation for other quality of service metric such as fade probability. © 2009-2012 IEEE.</p>