50175 research outputs found
Sort by
Boundary conditions and localization on AdS. Part I
No full textWe study the role of boundary conditions on the one loop partition function the N = 2 chiral multiplet of R-charge Delta on AdS(2) x S-1. The chiral multiplet is coupled to a background vector multiplet which preserves supersymmetry. We implement normalizable boundary conditions in AdS(2) and develop the Green's function method to obtain the one loop determinant. We evaluate the one loop determinant for two different actions: the standard action and the Q-exact deformed positive definite action used for localization. We show that if there exists an integer n in the interval D : (Delta-1/2L, Delta/2L), where L being the ratio of radius of AdS(2) to that of S-1, then the one loop determinants obtained for the two actions differ. It is in this situation that fields which obey normalizable boundary conditions do not obey supersymmetric boundary conditions. However if there are no integers in D, then fields which obey normalizable boundary conditions also obey supersymmetric boundary conditions and the one loop determinants of the two actions precisely agree. We also show that it is only in the latter situation that the one loop determinant obtained by evaluating the index of the D-10 operator associated with the localizing action agrees with the one loop determinant obtained using Green's function method
Vertically aligned and tree-like carbon nanostructures as anode of lithium ion battery
No full textA novel nanostructured carbon thin film, is synthesized by electron cyclotron plasma enhanced chemical vapor deposition and is proposed as the anode material for lithium ion battery. The individual nanostructures of the thin film have a multiwalled carbon nanotube, with carbon films attached to it, giving it a tree like appearance. All the nanostructures are aligned perpendicular to the surface of the substrate. The unique morphological structure and the vertical alignment provides for a large as well as unhindered area of interaction between the electrode material and the electrolyte. The cyclic voltammetry studies of the material with respect to lithium, shows that the lithium ions can be repeatedly intercalated and deintercalated to and from the material. On performing galvanostatic charge discharge cycling, the material has shown a lithiation capacity of 323 mu Ah.cm(-2)mu m(-1)(2590 mAh.g(-1)) and a delithiation capacity of 65 mu Ah.cm(-2)mu m(-1) (522 mAh.g(-1)) for the first cycle. The specific capacity after five cycles, during lithiation is 74 mu Ah.cm(-2) mu m(-1) (607 mAh.g(-1)) delithiation is 56 mu Ah.cm(-2)mu m(-1) (459 mAh.g(-1)). The reversible specific capacity for the material remains almost constant after this initial capacity loss up to 50 cycles
Embedding of a compactified Jacobian and theta divisors
No full textUsing a general stable vector bundle, we give an embedding aY of the compactified Jacobian J (Y) of an integral nodal curve Y into themoduli spaceUY (r, d) of semistable torsion free sheaves of rank r and degree d on Y. We also give an embedding of the normalisation J (Y) of J (Y) in the normalisation P(r, d) of UY (r, d). We determine a relation between the restriction of the theta line bundle on P(r, d) to J (Y) and the theta line bundle on J (Y). We show that the restriction of the Picard bundle Er, d on UY (r, d) to J (Y) is stable with respect to any theta divisor.J (Y) on J (Y) if d > r (2g - 1) and it is semistable if d = r (2g - 1). Finally we prove some results on natural cohomology
Crucial role of fragmented and isolated defects in persistent relaxation of deeply supercooled water
No full textProperties of water have been well elucidated for temperatures above similar to 230 K and yet mysteries remain in the deeply supercooled region. By performing extensive molecular dynamics simulations on this supercooled region, we find that structural and dynamical instabilities are hidden in the experimentally inaccessible region between 235 K and 150 K. We find a hitherto undiscovered fragmentation from 220 K to 190 K, which is the breakup of large clusters consisting of molecules with a locally distorted tetrahedral structure into small pieces with one or two isolated defects. The fragmentation leads to considerable changes in the relaxation dynamics of water. We reveal a crucial role of specific three-coordinated defects in slow but persistent structural relaxation. The presence of relaxation due to these specific defects makes the water glass transition temperature T-g (=136 K) extremely low and explains why the T-g of water is similar to 1/2 of the melting temperature T-m, much lower than the commonly obeyed 2/3 rule of T-g/T-m. Published by AIP Publishing
Photochemical detoxification of Cr(VI) using iron and saccharic acid: insights from cytotoxic and genotoxic assays
No full textHerein, we demonstrate rapid and complete photochemical detoxification of Cr(VI) by iron using saccharic acid (SA) as a sacrificial organic agent. 100% Cr(VI) (200 mu M) was reduced within 30 min using Fe(III) (50 mu M) and SA (300 mu M) under UV irradiation. The reaction mechanism involves photochemical recycling of Fe(III)/Fe(II) by SA via ligand to metal charge transfer (LMCT) along with the generation of a concomitant ligand radical and hydroperoxyl radical. Importantly, the MTT assay and gamma H2AX immunostaining were performed to evaluate the hitherto unexplored comparison of cytotoxicity and genotoxicity caused by untreated and treated aqueous Cr(VI). The results revealed that the Fe(III)/SA/UV treatment caused the complete removal of cytotoxic and genotoxic effects of Cr(VI) towards human cell lines. The presence of nitrate, chloride and natural organic matter increased the Cr(VI) reduction, while phosphate decreased the Cr(VI) reduction. Cu(II), Al(III) and Ni(II) had a positive effect on the Cr(VI) reduction. Furthermore, the Fe(III)/SA/UVC treatment caused almost complete Cr(VI) reduction in groundwater, lake water, and simulated galvanic wastewater. This study strongly supports the aptness of the Fe(III)/SA photochemical system for detoxification of Cr(VI) contaminated wastewater
Structural, spectral, computational, thermal and antibacterial studies on a co-crystal: 2-Aminopyrazine phthalic acid
No full textIn the present work, the crystal growth of a new co-crystal of aminopyrazine with phthalic acid (APPA) and the corresponding structural, vibrational, thermal and antibacterial characteristics have been reported. Crystals of aminopyrazine phthalicacid (PAPA) were grown by slow solvent evaporation technique. Single crystal X-ray diffraction analysis revealed that the present crystal structure is monoclinic system with P21/n space group. In the crystal structure, molecules were connected via N-H center dot center dot center dot O and O-H center dot center dot center dot N intermolecular hydrogen bonds with R-2(2)(8) and R-4(4)(18) ring motifs thus forming a C-2(2)(10) chain motif along the b axis. The crystal structure was dominated by N-H center dot center dot center dot O and weak O-H center dot center dot center dot N interactions and it was quantitatively analyzed by Hirshfeld surface and fingerprint analysis. The molecular geometry of the grown crystal was optimized theoretically by using density functional theory with B3LYP/cc-PVTZ basis set. The optimized molecular geometry and computed vibrational spectra were compared with experimental results which showed noteworthy agreement. Thermal stability was determined as 148 degrees C for APPA crystal using TG/DTA study. The atomic charge distribution on atoms of APPA molecule has been calculated by Mulliken charge analysis. Energy gap, ionization potential and chemical hardness of the APPA molecule were carried out by HOMO-LUMO plot. In which, the frontier orbitals has lower band gap value indicating the possible bio activity of the molecule. The natural bond orbital analysis was carried out to interpret the stability of the molecule and charge delocalization within the molecule. The antibacterial activity of the compound was tested and found increased significantly against all bacteria. Enhanced antibacterial activity of the APPA was attributed to the synergistic effects of intermolecular hydrogen-bonding interactions N-H center dot center dot center dot O and O-H center dot center dot center dot N between APZ and PA. The molecular docking study supported the antibacterial activity and exhibiting the binding energy. (C) 2018 Elsevier B.V. All rights reserved
Large nonlinear refraction in pulsed laser deposited BCZT thin films on quartz substrates
No full textOptical thin films based on ferroelectric materials are forerunners for novel optoelectronic and photonic applications due to their large inherent coupling between optical and electrical properties. We report here on the thickness dependence of linear and nonlinear optical properties of polycrystalline Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) thin films fabricated on quartz substrates by the pulsed laser deposition technique. In order to probe the linear optical properties of BCZT thin films, we have obtained optical transmission spectra from which the optical parameters like the refractive index and extinction coefficient were deduced using the Swanepoel method. Using the Sellemier relation, we have estimated the oscillator parameters like oscillator strength and oscillator energy from the refractive index dispersion data, which are indicative of the efficiency of the electro-optic coupling process. Further, the third-order optical nonlinearity of these thin films was measured by a closed-aperture Z-scan technique with a low-power, continuous-wave He-Ne laser as the excitation source. These films exhibited high optical nonlinearity, and the nonlinear refractive index was determined to be similar to 5 x 10(-7) m(2)/W. The enhanced nonlinear refraction in BCZT thin films at the low power regime could be attributed to both photothermal and photorefractive origin with a plausible larger contribution from the latter. Such a large nonlinear optical response exhibited at low optical powers in BCZT thin films is very promising technologically, as it may find applications in a number of photonic devices such as optical interconnects, optical processors, optical memories, and waveguide modulators. (C) 2018 Optical Society of America
WAVELET-BASED RECONSTRUCTION FOR UNLIMITED SAMPLING
No full textSelf-reset analog-to-digital converters (ADCs) allow for digitization of a signal with a high dynamic range. The reset action is equivalent to a modulo operation performed on the signal. We consider the problem of recovering the original signal from the measured modulo-operated signal. In our formulation, we assume that the underlying signal is Lipschitz continuous. The modulo-operated signal can be expressed as the sum of the original signal and a piecewise-constant signal that captures the transitions. The reconstruction requires estimating the piecewise-constant signal. We rely on local smoothness of the modulo-operated signal and employ wavelets with sufficient vanishing moments to suppress the polynomial component. We employ Daubechies wavelets, which are most compact for a given number of vanishing moments. The wavelet filtering provides a sequence consisting of a sum of scaled and shifted versions of a kernel derived from the wavelet filter. The transition locations are estimated from the sequence using a sparse recovery technique. We derive a sufficient condition on the sampling frequency for ensuring perfect reconstruction of the smooth signal. We validate our reconstruction technique on a signal consisting of sinusoids in both clean and noisy conditions and compare the reconstruction quality with the recently developed repeated finite-difference method
COMPARISON OF SPEECH TASKS FOR AUTOMATIC CLASSIFICATION OF PATIENTS WITH AMYOTROPHIC LATERAL SCLEROSIS AND HEALTHY SUBJECTS
No full textIn this work, we consider the task of acoustic and articulatory feature based automatic classification of Amyotrophic Lateral Sclerosis (ALS) patients and healthy subjects using speech tasks. In particular, we compare the roles of different types of speech tasks, namely rehearsed speech, spontaneous speech and repeated words for this purpose. Simultaneous articulatory and speech data were recorded from 8 healthy controls and 8 ALS patients using AG501 for the classification experiments. In addition to typical acoustic and articulatory features, new articulatory features are proposed for classification. As classifiers, both Deep Neural Networks (DNN) and Support Vector Machines (SVM) are examined. Classification experiments reveal that the proposed articulatory features outperform other acoustic and articulatory features using both DNN and SVM classifier. However, SVM performs better than DNN classifier using the proposed feature. Among three different speech tasks considered, the rehearsed speech was found to provide the highest F-score of 1, followed by an F-score of 0.92 when both repeated words and spontaneous speech are used for classification
