Department of Physics

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The recent measurement of RK∗ is yet another hint of new physics (NP) and supports the idea that it is present in b → sμμ- decays. We perform a combined model-independent and model-dependent analysis in order to deduce properties of this NP. Like others, we find that the NP must obey one of two scenarios: (I) Cμμ 9 NP < 0 or (II) Cμμ 9 NP = -Cμμ 10 NP < 0. A third scenario, (III) Cμμ 9 NP = -C0μμ 9 NP, is rejected largely because it predicts RK = 1, in disagreement with experiment. The simplest NP models involve the tree-level exchange of a leptoquark (LQ) or a Z0 boson.We show that scenario II can arise in LQ or Z0 models, but scenario I is only possible with a Z0. Fits to Z0 models must take into account the additional constraints from B0s - B0s mixing and neutrino trident production. Although the LQs must be heavy, O(TeV), we find that the Z0 can be light, e.g., MZ0 = 10 GeV or 200 MeV. © 2017 American Physical Society.

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Physical Review D

New physics in b → sμ+ μ-After the measurement of RK∗

We have prepared nano-structured In-doped (1 mol %) LiFePO4/C samples by sol-gel method followed by a selective high temperature (600 and 700 °C) annealing in a reducing environment of flowing Ar/H2 atmosphere. The crystal structure, particle size, morphology, and magnetic properties of nano-composites were characterized by X-ray diffraction (XRD), scanning electron microsopy (SEM), transmission electron microscopy (TEM), and 57Fe Mössbauer spectroscopy. The Rietveld refinement of XRD patterns of the nano-composites were indexed to the olivine crystal structure of LiFePO4 with space group Pnma, showing minor impurities of Fe2P and Li3PO4 due to decomposition of LiFePO4. We found that the doping of In in LiFePO4/C nanocomposites affects the amount of decomposed products, when compared to the un-doped ones treated under similar conditions. An optimum amount of Fe2P present in the In-doped samples enhances the electronic conductivity to achieve a much improved electrochemical performance. The galvanostatic charge/discharge curves show a significant improvement in the electrochemical performance of 700 °C annealed In-doped-LiFePO4/C sample with a discharge capacity of 142 mAh·g-1 at 1 C rate, better rate capability (~128 mAh·g-1 at 10 C rate, ~75% of the theoretical capacity) and excellent cyclic stability (96% retention after 250 cycles) compared to other samples. This enhancement in electrochemical performance is consistent with the results of our electrochemical impedance spectroscopy measurements showing decreased charge-transfer resistance and high exchange current density. © 2017 by the authors.

Inorganics

Optimization of electrochemical performance of LiFePO4/C by indium doping and high temperature annealing

We report a structural polymorphism of the S-DNA when a canonical B-DNA is stretched under different pulling protocols and provide a fundamental molecular understanding of the DNA stretching mechanism. Extensive all atom molecular dynamics simulations reveal a clear formation of S-DNA when the B-DNA is stretched along the 3′ directions of the opposite strands (OS3) and is characterized by the changes in the number of H-bonds, entropy, and free energy. Stretching along the 5′ directions of the opposite strands (OS5) leads to force induced melting form of the DNA. Interestingly, stretching along the opposite ends of the same strand leads to a coexistence of both the S- and melted M-DNA structures. We also do the structural characterization of the S-DNA by calculating various helical parameters. We find that the S-DNA has a twist of ∼10° which corresponds to a helical repeat length of ∼36 base pairs in close agreement with the previous experimental results. Moreover, we find that the free energy barrier between the canonical and overstretched states of DNA is higher for the same termini pulling protocol in comparison to all other protocols considered in this work. Overall, our observations not only reconcile with the available experimental results qualitatively but also enhance the understanding of different overstretched DNA structures. © 2017 Author(s).

Journal of Chemical Physics

Overstretching of B-DNA with various pulling protocols: Appearance of structural polymorphism and S-DNA

We used atomistic molecular dynamics simulations to study the properties of polymerized 1-alkene-3-butylimidazolium-hexafluorophosphate, a polymerized ionic liquid electrolyte, and characterized the influence of the linear alkene length on the mobility of the hexafluorophosphate ions. Consistent with experimental observations, our simulations indicate that as the alkene length increases, the diffusivity of hexafluorophosphate anion monotonically increases. We demonstrate that such a trend arises from the influence of linker segments on the intermolecular ion hopping rates, which is in turn modulated by intermolecular cationic separation distances. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1718–1723. © 2017 Wiley Periodicals, Inc.

Journal of Polymer Science, Part B: Polymer Physics

Influence of side chain linker length on ion-transport properties of polymeric ionic liquids

In this paper, simulation studies have been performed to analyze the role of plasma for sheet-electron beam propagation inside a drift space region filled with argon gas using particle-in-cell simulation code VSim6.2. The sheet-electron beam has been propagated inside the drift space of size 100 mm × 100 mm × 200 mm. A beam emitter of size 7 mm × 1 mm, which is equal to size of anode aperture, has been taken at the entrance of the drift space with identical operating conditions to the experiments, i.e., beam voltage 17 kV, beam current 156 A, and argon gas pressure 11 Pa. The transversal and longitudinal distribution of the sheet-electron beam is mainly dependent on beam voltage and current and also on gas pressure inside the drift space. The simulated images of the sheet-electron beam inside the drift space region have been compared with the experimental ones under these conditions. A good agreement has been found between the experimental and simulation results. This analysis has helped in obtaining transient plasma parameters, such as ion density, space charge neutralization time, and secondary electron temperature, simultaneously. These parameters are also analyzed at different operating conditions in the drift space region for sheet-beam stability. The operating condition at which a sheet-electron beam propagation up to 80 mm without any external magnetic field and instability has been obtained and the same has been explained on the basis of charge neutralization factor. © 1973-2012 IEEE.

IEEE Transactions on Plasma Science

Analysis of experimental results on pseudospark discharge-based electron beams with simulation model

A structurally simple dielectric barrier discharge based mercury-free plasma UV-light source has been developed for efficient water disinfection. The source comprises of a dielectric barrier discharge arrangement between two co-axial quartz tubes with an optimized gas gap. The outer electrode is an aluminium baked foil tape arranged in a helical form with optimized pitch, while the inner electrode is a hollow aluminium metallic rod, hermetically sealed. Strong bands peaking at wavelengths 172 nm and 253 nm, along with a weak band peaking at wavelength 265 nm have been simultaneously observed due to plasma radiation from the admixture of xenon and iodine gases. The developed UV source has been used for bacterial deactivation studies using an experimental setup that is an equivalent of the conventional house-hold water purifier system. Deactivation studies for five types of bacteria, i.e., E. coli, Shigella boydii, Vibrio, Coliforms and Fecal coliform have been demonstrated with 4 log reductions in less than ten seconds. © 2017 The Author(s).

Scientific Reports

Dielectric Barrier Discharge based Mercury-free plasma UV-lamp for efficient water disinfection

In this paper, a dielectric barrier discharge plasma based atmospheric pressure plasma jet has been generated in a floating helix and floating end ring electrode configuration using argon and helium gases. This configuration is subjected to a range of supply frequencies (10-25 kHz) and supply voltages (2-6 kV) at a fixed rate of gas flow rate (i.e., 1 l/min). The electrical characterization of the plasma jet has been carried out using a high voltage probe and current transformer. The current-voltage characteristics have been analyzed, and the consumed power has been estimated at different applied combinations for optimum power consumption at maximum jet length. The obtained optimum power and jet length for argon and helium gases are 12 mW and 32 mm, and 7.7 mW and 42 mm, respectively. It is inferred that besides the electrode configurations, the discharge gas is also playing a significant role in the low power operation of the cold plasma jet at maximum jet length. The obtained results are interpreted on the basis of penning processes. © 2017 Author(s).

Review of Scientific Instruments

A low power miniaturized dielectric barrier discharge based atmospheric pressure plasma jet

Chemical analysis of groundwater for a region is very important to the irrigation engineers and policy makers for site specific management of this important natural resource. Therefore, a study was planned to work out the chemical composition (Na+, Ca2+, Mg2+, K+, CO32-, HCO3-, Cl-, SO42-) and other quality parameters (pH, EC, SAR and RSC) of groundwater (117 samples) for Ellenbad block of Sirsa district, Haryana. Sodium and chloride were found as major anion and cation, respectively, in the groundwater samples. Through this chemical analysis, the groundwater quality of the block was interpreted according to three different classification criteria i.e. AICRP, USSL and Piper to check its suitability for irrigation purpose. To study the spatial distribution of different parameters (EC, pH and water quality according to AICRP criteria), thematic maps were generated using inverse distance technique in geographic information system. According to AICRP criteria, out of seven categories, maximum 44.4 % of samples were found in good and minimum 6.8 % were found in saline as well as in marginally alkali categories. According to USSL criteria, groundwater quality of the block was observed under C2S1, C3S1, C3S2, C4S2, C3S3, C4S3 and C4S4 categories. According to Piper criteria, 25.6 % samples was under good category (Ca2+-Mg2+-Cl- and Ca2+-Na+-HCO3- type) suitable for irrigation and 74.4 % was under poor category (Na+-Cl- type) unsuitable for irrigation. © 2017, Chemical Publishing Co. All rights reserved.

Asian Journal of Chemistry

Hydrochemical analysis and evaluation of groundwater quality of Ellenabad block of Sirsa district, India

The experimental study of a tapered, multi-gap, multi-aperture pseudospark-sourced electron gun based X-band plasma assisted slow wave oscillator is presented. The designed electron gun is based on the pseudospark discharge concept and has been used to generate a high current density and high energy electron beam simultaneously. The distribution of apertures has been arranged such that the field penetration potency inside the backspace of the hollow-cathode is different while passing through the tapered gap region. This leads to non-concurrent ignition of the discharge through all the channels which is, in general, quite challenging in the case of multi-aperture plasma cathode electron gun geometries. Multiple and successive hollow cathode phases are reported from this electron gun geometry, which have been confirmed using simulations. This geometry also has led to the achievement of ∼71% fill factor inside the slow wave oscillator for an electron beam of energy of 20 keV and a beam current density in the range of 115-190 A/cm2 at a working argon gas pressure of 18 Pa. The oscillator has generated broadband microwave output in the frequency range of 10-11.7 GHz with a peak power of ∼10 kW for ∼50 ns. © 2017 Author(s).

Applied Physics Letters

A tapered multi-gap multi-aperture pseudospark-sourced electron gun based X-band slow wave oscillator

Self-assembled hybrid perovskite quantum wells have attracted attention due to their tunable emission properties, ease of fabrication, and device integration. However, the dynamics of excitons in these materials, especially how they couple to phonons, remains an open question. Here, we investigate two widely used materials, namely, butylammonium lead iodide (CH3(CH2)3NH3)2PbI4 and hexylammonium lead iodide (CH3(CH2)5NH3)2PbI4, both of which exhibit broad photoluminescence tails at room temperature. We performed femtosecond vibrational spectroscopy to obtain a real-time picture of the exciton-phonon interaction and directly identified the vibrational modes that couple to excitons. We show that the choice of the organic cation controls which vibrational modes the exciton couples to. In butylammonium lead iodide, excitons dominantly couple to a 100 cm-1 phonon mode, whereas in hexylammonium lead iodide, excitons interact with phonons with frequencies of 88 and 137 cm-1. Using the determined optical phonon energies, we analyzed photoluminescence broadening mechanisms. At low temperatures (&lt;100 K), the broadening is due to acoustic phonon scattering, whereas at high temperatures, LO phonon-exciton coupling is the dominant mechanism. Our results help explain the broad photoluminescence line shape observed in hybrid perovskite quantum wells and provide insights into the mechanism of exciton-phonon coupling in these materials. © 2017 American Chemical Society.