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Facile embedding of gold nanostructures in the hole transporting layer for efficient polymer solar cells
No full textPhoton harvesting by the active layers of bulk heterojunction (BHJ) polymer solar cells (PSCs) greatly influences the power conversion efficiency (PCE) of the devices. Inclusion of novel metal nanostructures in photoactive layers is one of the effective ways to enhance light trapping without increasing the device thickness. Here, we demonstrate a dramatic enhancement (up to 43%) of the power conversion efficiency (PCE) by exploiting gold nanostructures (AuNSs)-embedded graphene oxide (GO) as the hole transporting layer (HTL) in BHJ PSCs. The enhancement of the device performance could be attributed to the increase in both short circuit current density (J(sc)) and fill factor (FF). The increased FF is most likely the result of the enhanced charge collection through modified HTL and anode contact. Furthermore, the optical properties of the photovoltaic devices suggest that AuNSs cause light trapping via plasmonic effects resulting enhanced J(sc)
Coccinia indica agglutinin, a 17 kDa PP2 like phloem lectin: Affinity purification, primary structure and formation of self-assembled filaments
No full textPhloem protein-2 (PP2) is an abundant soluble protein in the sieve elements in plants. Its lectin property was reported in various species. The primary structure of a 17 kDa PP2 from Coccinia indica (Coccinia indica agglutinin, CIA17), determined by mass spectrometry, shows extensive homology with PP2 super family phloem lectins. Analysis of mass spectrometric data indicated the presence of 16 potential allelic variants of CIA17 with insignificant divergence in the primary structure. The primary structure contains an intramolecular disulfide bridge between Cys-34 and Cys-51, which is conserved across various cucurbit species and hence likely to be important for carbohydrate binding. CD spectroscopic studies revealed that CIA17 is rich in antiparallel 13-sheets, similar to PP2 proteins from Cucurbita maxima and Arabidopsis thaliana. CD spectra recorded at various temperatures showed very little change in the spectral intensity and shape up to 90 degrees C, suggesting that CIA17 is a highly thermostable protein. Atomic force microscopic studies revealed that CIA17 forms filamentous structures at higher concentrations. In light of these results, we propose that CIA17 and other PP2 proteins play a role in the plant defense against pathogens by directly binding with the chitin cell wall, and also promote wound healing by forming self-assembled filaments. (C) 2017 Elsevier B.V. All rights reserved
Towards a bootstrap approach to higher orders of epsilon expansion
No full textWe employ a hybrid approach in determining the anomalous dimension and OPE coefficient of higher spin operators in the Wilson-Fisher theory. First we do a large spin analysis for CFT data where we use results obtained from the usual and the Mellin Bootstrap and also from Feynman diagram literature. This gives new predictions at O(epsilon(4)) and O(epsilon(5)) for anomalous dimensions and OPE coefficients, and also provides a cross-check for the results from Mellin Bootstrap. These higher orders get contributions from all higher spin operators in the crossed channel. We also use the Bootstrap in Mellin space method for phi(3) in d = 6 - epsilon CFT where we calculate general higher spin OPE data. We demonstrate a higher loop order calculation in this approach by summing over contributions from higher spin operators of the crossed channel in the same spirit as before
Influence of silver nanoparticles on titanium oxide and nitrogen doped titanium oxide thin films for sun light photocatalysis (vol 436, pg 708, 2018)
No full textA study of the effect of bulges on bar formation in disc galaxies
No full textWe use N-body simulations of bar formation in isolated galaxies to study the effect of bulge mass and bulge concentration on bar formation. Bars are global disc instabilities that evolve by transferring angular momentum from the inner to outer discs and to the dark matter halo. It is well known that a massive spherical component such as halo in a disc galaxy can make it bar stable. In this study, we explore the effect of another spherical component, the bulge, on bar formation in disc galaxies. In our models, we vary both the bulge mass and concentration. We have used two sets of models: one that has a dense bulge and high surface density disc, and the other model has a less concentrated bulge and a lighter disc. In both models, we vary the bulge to disc mass fraction from 0 to 0.7. Simulations of both the models show that there is an upper cut-off in bulge-to-disc mass ratio M-b/M-d above which bars cannot form; the cut-off is smaller for denser bulges (M-b/M-d = 0.2) compared to less denser ones (M-b/M-d = 0.5). We define a new criterion for bar formation in terms of the ratio of bulge to total radial force (F-b/F-tot) at the disc scale lengths above which bars cannot form. We find that if F-b/F-tot > 0.35, a disc is stable and a bar cannot form. Our results indicate that early-type disc galaxies can still form strong bars in spite of having massive bulges
Asymmetric Pulse Modeling for FRI Sampling
No full textWe consider sampling and reconstruction of finite-rate-of-innovation (FRI) signals such as a train of pulses, where the pulses have varying degrees of asymmetry. We address the problem of asymmetry modeling starting from a given symmetric prototype. We show that among the class of unitary operators that are linear and invariant to translation and scale, the fractional Hilbert (FrH) operator is unique for parametrically modeling pulse asymmetry. The FrH operator is obtained by a trigonometric interpolation between the standard Hilbert and identity operators, where the interpolation weights are determined by the degree of asymmetry. The FrH operators are also steerable, which allows for estimation of the asymmetry factors, in addition to the delays and amplitudes, using the high-resolution spectral estimation techniques that are used for solving standard FRI problems. We also develop the discrete counterpart using discrete FrH operators and show that all the desirable properties carry over smoothly to the discrete setting as well. We derive closed-form expressions for the Cramer-Rao bounds and Hammersley-Chapman-Robbins bound, on the variances of the estimators for continuous and discrete parameters, respectively. Experimental results show that the proposed estimators have variances that meet the lower bounds. We demonstrate an application of the proposed discrete FrH methodology on real electrocardiogram (ECG) signals in the presence of noise. Specifically, we show how the asymmetry of QRS complexes in various channels of an ECG signal could be modeled accurately
Effect of finite disk-thickness on swing amplification of non-axisymmetric perturbations in a sheared galactic disk
No full textA typical galactic disk is observed to have a finite thickness. Here, we present the study of the physical effect of introduction of finite thickness on the generation of small-scale spiral arms by swing amplification in a differentially rotating galactic disk. The galactic disk is modelled first as a one-fluid system, and then as a gravitationally-coupled two-fluid (stars and gas) system where each fluid is taken as isothermal, and corotating with each other. We derived the equations governing the evolution of the non-axisymmetric perturbations in a sheared frame of reference while incorporating the effect of finite thickness of a galactic disk. We found that the finite thickness of a galactic disk has a generic trend of suppressing the growth of the non-axisymmetric perturbations via swing amplification. Moreover, even the observed range of disk-thickness values (similar to 300-500 pc) can lead to a complete suppression of swing amplification for Q similar to 1.7, whereas for an infinitesimally-thin disk, the corresponding critical value is Q similar to 2. For a two-fluid (stars and gas) system, the net amplification is shown to be set by the mutual interplay of the effect of interstellar gas in promoting the spiral features and the effect of finite thickness in preventing the spiral arms. The coexistence of these two opposite effects is shown to be capable of giving rise to diverse and complex dynamical behaviour
Tuning of geometric nonlinearity in ultrathin nanoelectromechanical systems
No full textNonlinearities in nanoelectromechanical systems (NEMS) play a vital role in dynamics of the device. Clear understanding of nonlinearities and ability to tune and manipulate them to enhance the performance are crucial for applications with these devices. Here, we utilize an electrostatic mechanism to tune the geometric nonlinearity of an atomically thin NEMS. The exquisite tuning enables us to demonstrate hardening, softening, and mixed nonlinear responses in the device. The electrostatic tuning over the nonlinearity is utilized to effectively nullify Duffing nonlinearity in a specific regime. The observed mixed nonlinear response is the result of cross coupling between strong quadratic and quartic nonlinearities, an aspect explained by method of multiple scale analysis. Published by AIP Publishing
Salt Effects on Protein Folding Thermodynamics
No full textSalts differ in their ability to stabilize protein conformations, thereby affecting the thermodynamics and kinetics of protein folding. We developed a coarse-grained protein model that can predict salt-induced changes in protein properties by using the transfer free-energy data of various chemical groups from water to salt solutions. Using this model and molecular dynamics simulations, we probed the effect of seven different salts on the folding thermodynamics of the DNA binding domain of lac repressor protein (lac-DBD) and N-terminal domain of ribosomal protein (NTL9). We show that a salt can act as a protein stabilizing or destabilizing agent depending on the protein sequence and folded state topology. The computed thermodynamic properties, especially the m values for various salts, which reveal the relative ability of a salt to stabilize the protein folded state, are in quantitative agreement with the experimentally measured values. The computations show that the degree of protein compaction in the denatured ensemble strongly depends on the salt identity, and for the same variation in salt concentration, the compaction in the protein dimensions varies from similar to 4% to similar to 30% depending on the salt. The transition-state ensemble (TSE) of lac-DBD is homogeneous and polarized, while the TSE of NTL9 is heterogeneous and diffusive. Salts induce subtle structural changes in the TSE that are in agreement with Hammonds postulate. The barrier to protein folding tends to disappear in the presence of moderate concentrations (similar to 34-m) of strongly stabilizing salts
Investigation of fast and sizeable photostriction effect in tellurium thin films using fiber Bragg grating sensors
No full textWe report a sizeable photoinduced strain in 90 nm tellurium (Te) thin film, coated on a fiber Bragg grating (FBG) sensor. The Bragg wavelength shift of the FBG sensor is used as the probe, to understand the photostrictive properties of Te thin film under illumination with laser light of visible wavelengths (405, 532 and 633 nm), at varying optical power density (5-161 mW/mm(2)), and also during cyclic exposure. An induced elastic strain of the order of 10(-5) to 10(-4) has been observed which is found to increase with increasing wavelength of laser illumination. The high (1 pm) resolution of the FBG interrogator used facilitates the accurate detection of the elastic strain induced in Te thin films even at a short exposure time of 0.1 s. (C) 2018 Elsevier B.V. All rights reserved