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Variation of the donor and acceptor in D-A-pi-A based cyanopyridine dyes and its effect on dye sensitized solar cells
No full textTwo metal free organic dyes (TPCTh and TPCRh) with D-A-pi-A configuration, having 3-cyanopyridine as an auxiliary acceptor and thiophene pi-linkers along with a triphenylamine donor and cyanoacetic acid/rhodanine-3-acetic acid anchoring groups, were successfully synthesized and utilized as sensitizers in the fabrication of dye-sensitized solar cells (DSSCs). The opto-electronic properties of TPCTh and TPCRh were compared with the model sensitizer CCTh having carbazole as the donor and cyanoacetic acid as the anchoring group. Both the dyes showed red shifted absorption spectra compared to the standard CCTh dye. Also, TPCRh showed a broader absorption spectrum with a reduced band gap compared to TPCTh. However, theoretical studies indicate that the unavailability of excited state conjugation over the anchoring group could lead to restricted charge injection for the TPCRh dye, whereas the TPCTh dye exhibits complete conjugation over the entire molecule. The photovoltaic performance of the TPCTh dye was found to be better compared with the standard CCTh sensitizer as a result of better absorption contributed by the lower band gap in TPCTh leading to improved photon-light conversion and thus an improved J(sc) of 11 mA cm(-2) over the 7.12 mA cm(-2) of CCTh. In addition, lifetime measurements corroborated a lower electron lifetime for TPCRh compared to TPCTh and CCTh
Spectroscopic and computational insights into the ion-solvent interactions in hydrated aprotic and protic ionic liquids
No full textIonic liquids (ILs) and their aqueous solutions are emerging media for solving and manipulating biochemical molecules such as proteins. Unleashing the full potential however requires a detailed mechanistic understanding of how suitable protic and aprotic ILs behave in the presence of water in the first place. The present work aims at making an important step by performing a combined experimental and computational study of two selected ILs and their mixtures with water: the aprotic cholinium propionate (Chl]Pro]) and the protic N-methyl-2-pyrrolidonium propionate (NMP]Pro]). IR and Raman spectroscopy reveal stronger ion-solvent interactions in Chl]Pro]-H2O systems compared to NMP]Pro]-H2O mixtures. This can be explained by the tightly packed ion-pair associations in NMP]Pro] comprising the protic -N+-H counterpart, which allows the establishment of highly directional and strong interionic hydrogen bonds. The spectral decomposition of the O-D stretching band into three sub-peaks showed that the protic NMP]Pro] favors the self-association of water molecules. On the other hand, the predominant fraction of water-anion/cation aggregates exists in aprotic Chl]Pro]. These hydrated systems can be envisaged using quantum-chemical calculations in the following way: H2O center dot center dot center dotChl](+)center dot center dot center dot H2O center dot center dot center dotPro](-)center dot center dot center dot H2O and H2O center dot center dot center dotNMP](+)Pro](-)center dot center dot center dot H2O, which implied preferable solvent-shared ion-pair (SIP) configurations for Chl]Pro]-H2O systems, whereas the contact ion-pair (CIP) state prevails for the NMP]Pro]-H2O systems. The latter holds even in the water-rich regime. In future work, these findings will be the basis for an understanding of the underlying principles that govern the interactions of ions with bio-molecules in aqueous solutions
Selective Synthesis of N-H and N-Aryl Benzotriazoles by the 3+2] Annulation of Sodium Azide with Arynes
No full textThe synthetic utility of NaN3 as the azide component in the 3 + 2] annulation with arynes generated from 2-(trimethylsilyl)aryltriflates resulting in the transition-metal-free synthesis of N-H and N-aryl benzotriazoles has been demonstrated. Using CsF as the fluoride source in CH3CN, the N-H benzotriazoles are formed in high selectivity instead of the expected azidobenzene. Interestingly, N-aryl benzotriazoles are formed using KF and THF as solvent in an open-flask reaction. Moreover, a method for the N1-arylation of benzotriazole is also presented
Hypoxic Non-replicating Persistent Mycobacterium tuberculosis Develops Thickened Outer Layer That Helps in Restricting Rifampicin Entry
No full textBacteria undergo adaptive morphological changes to survive under stress conditions. The present work documents the morphological changes in Mycobacterium tuberculosis (Mtb) cells cultured under hypoxic condition using Wayne's in vitro hypoxia model involving non-replicating persistence stages 1 and 2 (NRP stage 1 and NRP stage 2) and reveals their physiological significance. Transmission electron microscopy of the NRP stage 2 cells showed uneven but thick outer layer (TOL), unlike the evenly thin outer layer of the actively growing mid-log phase (MLP) cells. On the contrary, the saprophytic Mycobacterium smegmatis NRP stage 2 cells lacked TOL. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) of the Mtb NRP stage 2 cells confirmed the rough uneven surface unlike the smooth surface of the MLP cells. Zeta potential measurements showed high negative charge on the surface of NRP stage 2 cells and polysaccharide specific calcofluor white (CFW) staining of the cells revealed high content of polysaccharide in the TOL. This observation was supported by the realtime PCR data showing high levels of expression of the genes involved in the synthesis of sugars, such as trehalose, mannose and others, which are implicated in polysaccharide synthesis. Experiments to understand the physiological significance of the TOL revealed restricted entry of the biologically low-active 5-carboxyfluorescein-rifampicin (5-FAMRIF), at concentrations equivalent to microbicidal concentrations of the unconjugated biologically active rifampicin, into the NRP stage 2 cells, unlike in the MLP cells. Further, as expected, mechanical removal of the TOL by mild bead beating or release of the NRP stage 2 cells from hypoxia into normoxia in fresh growth medium also significantly increased 5-FAM-RIF permeability into the NRP stage 2 cells to an extent comparable to that into the MLP cells. Taken together, these observations revealed that Mtb cells under hypoxia develop TOL that helps in restricting rifampicin entry, thereby conferring rifampicin tolerance
(A,delta)-modules, Hochschild homology and higher derivations
No full textIn this paper, we develop the theory of modules over (A,delta), where A is an algebra and delta :A?A is a derivation. Our approach is heavily influenced by Lie derivative operators in noncommutative geometry, which make the Hochschild homologies HH.(A) of A into a module over (A,delta). We also consider modules over (A,Delta), where Delta={Delta n}n >= 0 is a higher derivation on A. Further, we obtain a Cartan homotopy formula for an arbitrary higher derivation on A
Extreme Contractions on Finite-Dimensional Polygonal Banach Spaces
No full textWe explore extreme contractions on finite-dimensional polygonal Banach spaces, from the point of view of attainment of norm of a linear operator. We prove that if X is an n-dimensional polygonal Banach space and Y is any normed linear space and T is an element of L(X, Y) is an extreme contraction, then T attains norm at n linearly independent extreme points of B-X. Moreover, if T attains norm at n linearly independent extreme points x(1), x(2), ..., x(n), of B-X and does not attain norm at any other extreme point of B-X, then each T-x(i), is an extreme point of B-Y. We completely characterize extreme contractions between a finite-dimensional polygonal Banach space and a strictly convex normed linear space. We introduce L-P property for a pair of Banach spaces and show that it has natural connections with our present study. We also prove that for any strictly convex Banach space X and any finite-dimensional polygonal Banach space Y, the pair (X, Y) does not have L-P property. Finally, we obtain a characterization of Hilbert spaces among strictly convex Banach spaces in terms of L-P property
Locally periodic unfolding operator for highly oscillating rough domains
No full textThis article aims to understand the locally periodic oscillating domain via unfolding operators. A three-dimensional rough domain Omega epsilon, epsilon >0 a small parameter, has been considered for the study where the boundary is rapidly oscillating with high amplitude. Though there are some articles with locally periodic boundary oscillations with small amplitude we do not see any literature with high-amplitude (O(1)) locally periodic oscillating domains. In this article, we attempt to study a problem in locally periodic rough domains with an eye towards the general oscillating domains without periodicity. With our experience of handling such domains and unfolding operators, we develop locally periodic unfolding operators to study our problems. We consider a nonlinear inhomogeneous Robin boundary value problem posed on this domain to demonstrate the utility of the newly defined operator
Application of bending creep for examining effect of service conditions on creep response of steel
No full textWe demonstrate that creep testing of cantilevers in bending is suitable for evaluating steady-state creep parameters, including the stress exponent. In particular, a low alloy bainitic boiler tube steel, namely T11, in as-fabricated condition and after 27 years of service in a coal-fired power-plant were tested in bending at 600 degrees C at effective steady-state stresses of 100-200 MPa. Steady-state strain rates obtained from the bending tests matched reasonably well with those obtained from uniaxial compression tests performed at equivalent stresses, thereby unambiguously validating the bending test methodology for the entire range of stress. All types of samples showed a stress exponent of 6; however, the steady-state strain rates of the in-service samples were similar to 7 times larger than those of as-fabricated samples. Although this suggests a substantial loss in the creep resistance of the tubes at the end of the design-life, the ``to-be-discarded'' tube may still have considerable residual life. Microstructural evaluation of the samples revealed coarsening of carbides in bainite and metal enrichment of carbides, with excess of M6C, with exposure to the service conditions. A structure-property correlation is established to explain the experimental observations, and results are discussed in light of existing literature
Synthesis, growth, structural, thermal, third order nonlinear and computational studies of organic single crystal: 2-Amino-4-picolinium 2-chloro-4-nitrobenzoate
No full textNovel organic third-order nonlinear optical material, 2-Amino-4-picolinium-2-chloro-4-nitrobenzoate (2A4P2C4N) was synthesized and grown into single crystal by slow solvent evaporation method at room temperature. Single crystal X-ray diffraction analysis reveals that the title compound crystallizes in monoclinic crystal system with a centrosymmetric space group of P2(1)/n. From UV-Visible spectrum, the optical transparency and band gap were determined. Thermal stability of the title material was established by thermogravimetry (TG) and differential thermal analysis (DTA) analyses. The third-order nonlinear susceptibility was determined experimentally and it was found to be 2.56 x 10(-8) esu. The quantum chemical calculations were performed to analyze Hirshfeld surface, electrostatic potential, HOMO-LUMO and global quantum chemical reactivity descriptors of the titled molecule at B3LYP/6-311 + + G (d,p) level of theory. A comparative analysis computationally calculated showed that the < gamma > amplitude for 2A4P2C4N molecule was found to be three 3 times greater than that of compared para-Nitroaniline (p-NA)