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131.
132.
Ganesan Karthik Dr. Jong Min Lim Dr. A. Srinivasan Dr. C. H. Suresh Prof. Dr. Dongho Kim Prof. Dr. Tavarekere K. Chandrashekar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(50):17011-17020
Two examples of core‐modified 36π doubly fused octaphyrins that undergo a conformational change from a twisted figure‐eight to an open‐extended structure induced by protonation are reported. Syntheses of the two octaphyrins (in which Ar=mesityl or tolyl) were achieved by a simple acid‐catalyzed condensation of dipyrrane unit containing an electron‐rich, rigid dithienothiophene (DTT) core with pentafluorobenzaldehyde followed by oxidation with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ). The single‐crystal X‐ray structure of the octaphyrin (in which Ar=mesityl) shows a figure‐eight twisted conformation of the expanded porphyrin skeleton with two DTT moieties oriented in a staggered conformation with a π‐cloud distance of 3.7 Å. Spectroscopic and quantum mechanical calculations reveal that both octaphyrins conform to a [4n]π nonaromatic electronic structure. Protonation of the pyrrole nitrogen atoms of the octaphyrins results in dramatic structural change, which led to 1) a large redshift and sharpening of absorption bands in electronic absorption spectrum, 2) a large change in chemical shift of pyrrole β‐CH and ? NH protons in the 1H NMR spectrum, 3) a small increase in singlet lifetimes, and 4) a moderate increase in two‐photon absorption cross‐section values. Furthermore, nucleus‐independent chemical shift (NICS) values calculated at various geometrical positions show positive values and anisotropy‐induced current density (AICD) plots indicate paratropic ring‐currents for the diprotonated form of the octaphyrin (in which Ar=tolyl); the single‐crystal X‐ray structure of the diprotonated form of the octaphyrin shows an extended structure in which one of the pyrrole ring of each dipyrrin subunit undergoes a 180 ° ring‐flip. Four trifluoroacetic acid (TFA) molecules are bound above and below the molecular plane defined by meso‐carbon atoms and are held by N? H ??? O, N? H ??? F, and C? H ??? F intermolecular hydrogen‐bonding interactions. The extended‐open structure upon protonation allows π‐delocalization and the electronic structure conforms to a [4n]π Hückel antiaromatic in the diprotonated state. 相似文献
133.
Maheshwari Gourab Subramanian Ganesa Sundararajan Karthik Arumugam Ranjithkumar Averineni Ginjupalli Prashant Musmade Kishore Udupa Nayanabhirama 《平面色谱法杂志一现代薄层色谱法》2007,20(5):335-339
JPC – Journal of Planar Chromatography – Modern TLC - A sensitive, accurate, precise, and stability-indicating high-performance thin-layer chromatographic method has been established... 相似文献
134.
Yoshiaki Sasaki Jota Suzuki Hiroki Inage Ryota Emori Shinji Tanosaki Tetsuya Yuasa Michiaki Takagi Akira Ishikawa Hiroshi Taniguchi Balasigamani Devaraj Takao Akatsuka 《Optical Review》2003,10(5):462-465
We recently proposed and developed a novel transillumination laser computed tomography (CT) imaging system using a fiber-optic method based on coherent detection imaging (CDI) for biomedical use. Use of optical fibers enables portability and robustness against environmental changes in a room, such as variable temperature, air-flow shifts, and unexpected vibrations. In addition, motion-artifact-free images can be obtained because measurements can be performed with the object fixed. In the present paper, we experimentally investigate in detail the fundamental imaging properties of the system, which has a spatial resolution of 500 μm, a dynamic range of approximately 120 dB, and a minimum-detectable-optical power of 10−14W as a result of the excellent properties of the heterodyne detection. Based on experimental observations, the proposed system can reconstruct tomographic images of highly scattering objects in the transillumination mode, similar to X-ray CT, at sub-millimeter spatial resolution and with quantitativeness. Finally, we demonstrate with experiments using a physical phantom that the imaging system possesses high resolution and quantitative imaging abilities for highly scattering objects. 相似文献
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136.
Sankaranarayanan Kavitha Ramachandran Raja Prabhu Kumar Raghavan Muralitharen Sinthu S. Mansoor Usman M. Sriram Kumar V. Madan Kumar S. Vignesh V. Malini K.M. Cherian S. Madhivanan Sankaranarayanan Karthik Natarajan Arutselvan Sundararajan Raji 《Journal of Electrostatics》2011,69(4):267-274
Clinically chemo-resistant types of cancers do not respond well to conventional therapies. To treat and enhance the efficacy of drug delivery for these cancers, we have developed an in vitro model of a combination therapy using adult human mesenchymal stem cells, electrical pulses and chemo drug. Adult Mesenchymal stem cells were used because they are similar to cancer stem cells which cause the tumor to be chemo- and radiation resistant. These cells, derived from human adult bone marrow were subjected to low voltage, long duration (200 V/cm, 40 ms and 450 V/cm, 25 ms) and high voltage, short duration (1200 V/cm, 100 μs) pulses. The effect of these voltages on the viability and proliferation ability of these cells in the presence and absence of Bleomycin (chemodrug used for treating various cancers, FDA approved in US and other respective medical agencies in other countries,) indicate the potential of transfer of this technique to clinical practice for effective electro-targeted stem cell therapy. 相似文献
137.
Copper and niobium are mutually immiscible in the solid state and exhibit a large positive enthalpy of mixing in the liquid state. Using vapour quenching via magnetron co-sputter deposition, far-from equilibrium amorphous Cu–Nb films have been deposited which exhibit a nanoscale phase separation. Annealing these amorphous films at low temperatures (~200?°C) initiates crystallization via the nucleation and growth of primary nanocrystals of a face-centred cubic Cu-rich phase separated by the amorphous matrix. Interestingly, subsequent annealing at a higher temperature (>300?°C) leads to the polymorphic nucleation and growth of large spherulitic grains of a body-centred cubic Nb-rich phase within the retained amorphous matrix of the partially crystallized film. This sequential two-stage crystallization process has been investigated in detail by combining transmission electron microscopy [TEM] (including high-resolution TEM) and atom probe tomography studies. These results provide new insights into the crystallization behaviour of such unusual far-from equilibrium phase-separated metallic glasses in immiscible systems. 相似文献
138.
The proton second moment (M 2) and spin-lattice relaxation time (T 1) have been measured in (NH4)2ZnBr4 in the range 77–300 K. The room-temperature spectrum shows a structure which disappears around 243 K. The signal is strong and narrow even at 77 K. Proton T 1 shows a maximum at 263 K, caused by spin rotation interaction and decreases with decreasing temperature till 235 K, where it shows a sudden increase. Below 235 K, again it decreases and shows a slope change around 216.5 K (reported Tc ). From 216.5 K, T 1 decreases continuously without exhibiting any minimum down to 77 K. The narrow line at 77 K, and absence of a T 1 minimum down to 77 K indicate the possibility of quantum mechanical tunnelling in this system. Motional parameters such as activation energy and pre-exponential factor have been evaluated for the reorientational motion of the NH+ 4 ion. 相似文献
139.
140.
Ru‐Catalysed CH Arylation of Indoles and Pyrroles with Boronic Acids: Scope and Mechanistic Studies
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Carina Sollert Karthik Devaraj Dr. Andreas Orthaber Dr. Paul J. Gates Dr. Lukasz T. Pilarski 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5380-5386
The Ru‐catalysed C2?H arylation of indoles and pyrroles by using boronic acids under oxidative conditions is reported. This reaction can be applied to tryptophan derivatives and tolerates a wide range of functional groups on both coupling partners, including bromides and iodides, which can be further derivatised selectively. New indole‐based ruthenacyclic complexes are described and investigated as possible intermediates in the reaction. Mechanistic studies suggest the on‐cycle intermediates do not possess a para‐cymene ligand and that the on‐cycle metalation occurs through an electrophilic attack by the Ru centre. 相似文献