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101.
Rituparna Biswas Yumi Ida Dr. Michael L. Baker Saptarshi Biswas Paramita Kar Prof. Dr. Hiroyuki Nojiri Prof. Dr. Takayuki Ishida Prof. Dr. Ashutosh Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(12):3943-3953
Three new trinuclear nickel (II) complexes with the general composition [Ni3L3(OH)(X)](ClO4) have been prepared in which X=Cl? ( 1 ), OCN? ( 2 ), or N3? ( 3 ) and HL is the tridentate N,N,O donor Schiff base ligand 2‐[(3‐dimethylaminopropylimino)methyl]phenol. Single‐crystal structural analyses revealed that all three complexes have a similar Ni3 core motif with three different types of bridging, namely phenoxido (μ2 and μ3), hydroxido (μ3), and μ2‐Cl ( 1 ), μ1,1‐NCO ( 2 ), or μ1,1‐N3 ( 3 ). The nickel(II) ions adopt a compressed octahedron geometry. Single‐crystal magnetization measurements on complex 1 revealed that the pseudo‐three‐fold axis of Ni3 corresponds to a magnetic easy axis, being consistent with the magnetic anisotropy expected from the coordination structure of each nickel ion. Temperature‐dependent magnetic measurements indicated ferromagnetic coupling leading to an S=3 ground state with 2J/k=17, 17, and 28 K for 1 , 2 , and 3 , respectively, with the nickel atoms in an approximate equilateral triangle. The high‐frequency EPR spectra in combination with spin Hamiltonian simulations that include zero‐field splitting parameters DNi/k=?5, ?4, and ?4 K for 1 , 2 , and 3 , respectively, reproduced the EPR spectra well after a anisotropic exchange term was introduced. Anisotropic exchange was identified as Di,j/k=?0.9, ?0.8, and ?0.8 K for 1 , 2 , and 3 , respectively, whereas no evidence of single‐ion rhombic anisotropy was observed spectroscopically. Slow relaxation of the magnetization at low temperatures is evident from the frequency‐dependence of the out‐of‐phase ac susceptibilities. Pulsed‐field magnetization recorded at 0.5 K shows clear steps in the hysteresis loop at 0.5–1 T, which has been assigned to quantum tunneling, and is characteristic of single‐molecule magnets. 相似文献
102.
Sudipta Chakraborty K. V. Vimalnath A. Rajeswari H. D. Sarma Ajit Shinto E. R. Radhakrishnan Ashutosh Dash 《Journal of Radioanalytical and Nuclear Chemistry》2014,302(2):875-881
Hydroxyapatite (HA) [Ca10(PO4)6(OH)2] particles radiolabeled with a variety of β? emitting lanthanide radionuclides and also pseudolanthanide 90Y have been proposed for the treatment of arthritis. A ready-to-use cold kit of HA particles (1–10 µm size) was developed for fast and convenient formulation of radiolanthanide-labeled HA particles at hospital radiopharmacy. Six radionuclides namely, 169Er, 177Lu, 153Sm, 166Ho, 142Pr and 90Y, having β? emissions of a wide range of energy [Eβ(max) = 0.34–2.28 MeV] were identified and produced by thermal neutron activation. Clinical doses of HA particles labeled with these radionuclides were prepared in high yield (>97 %) and radiochemical purity (>99 %) using the cold kits. Pre-clinical studies of 177Lu–HA carried out in Wistar rats bearing arthritis in knee joints revealed no leakage of the activity from the joints. In preliminary clinical investigation using 333 ± 46 MBq doses of the same preparation, significant improvement in the disease conditions was reported in patients with chronic rheumatoid arthritis of knee joints. 相似文献
103.
Carroll MJ Gromova AV Miller KR Tang H Wang XS Tripathy A Singleton SF Collins EJ Lee AL 《Journal of the American Chemical Society》2011,133(16):6422-6428
Structure-based drug design relies on static protein structures despite significant evidence for the need to include protein dynamics as a serious consideration. In practice, dynamic motions are neglected because they are not understood well enough to model, a situation resulting from a lack of explicit experimental examples of dynamic receptor-ligand complexes. Here, we report high-resolution details of pronounced ~1 ms time scale motions of a receptor-small molecule complex using a combination of NMR and X-ray crystallography. Large conformational dynamics in Escherichia coli dihydrofolate reductase are driven by internal switching motions of the drug-like, nanomolar-affinity inhibitor. Carr-Purcell-Meiboom-Gill relaxation dispersion experiments and NOEs revealed the crystal structure to contain critical elements of the high energy protein-ligand conformation. The availability of accurate, structurally resolved dynamics in a protein-ligand complex should serve as a valuable benchmark for modeling dynamics in other receptor-ligand complexes and prediction of binding affinities. 相似文献
104.
CFD analysis for thermo-hydraulic properties in a tubular heat exchanger using curved circular rings
Singh Satyendra Kharkwal Himanshi Gautam Abhishek Pandey Ashutosh 《Journal of Thermal Analysis and Calorimetry》2020,141(6):2211-2218
Journal of Thermal Analysis and Calorimetry - The never-ending demands of humans have led researchers to find more efficient energy conversion technologies. Enhancing heat transfer rate in a... 相似文献
105.
Ruby Upadhyay Mridula Tripathi Priyanka Chawla Ashutosh Pandey 《Journal of Solid State Electrochemistry》2014,18(7):1889-1892
Extracts from roots of Beta vulgaris were used as natural sensitizers of a wide-bandgap semiconductor (CeO2–TiO2) in photoelectrochemical solar cells. The natural dye, adsorbed onto the semiconductor surface, absorbs visible light and promotes electron transfer across the dye/semiconductor interface. We have applied CeO2–TiO2 to natural dye sensitizer solar cells as a photoelectrode to reduce the charge recombination rate by providing energy barrier at the interface between the photoanode and electrolyte which offers an improvement of photovoltaic efficiency. Short-circuit current density (J sc) and open-circuit voltages (V oc) of 9.0 mA cm?2 and 680 mV, respectively, were obtained, and an effective energy conversion efficiency of 3.5?% was achieved. This simple and cheap technique of cell preparation opens up a perspective of commercial feasibility for inexpensive and environment-friendly dye cells. 相似文献
106.
Hydroxo‐Bridged Dimers of Oxo‐Centered Ruthenium(III) Triangle: Synthesis and Spectroscopic and Theoretical Investigations
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Apoorva Upadhyay Jitendrasingh Rajpurohit Mukesh Kumar Singh Richa Dubey Anant Kumar Srivastava Prof. Dr. Ashutosh Kumar Prof. Dr. Gopalan Rajaraman Prof. Dr. Maheswaran Shanmugam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(20):6061-6070
The homometallic hexameric ruthenium cluster of the formula [RuIII6(μ3‐O)2(μ‐OH)2((CH3)3CCO2)12(py)2] ( 1 ) (py=pyridine) is solved by single‐crystal X‐ray diffraction. Magnetic susceptibility measurements performed on 1 suggest that the antiferromagnetic interaction between the RuIII centers is dominant, and this is supported by theoretical studies. Theoretical calculations based on density functional methods yield eight different exchange interaction values for 1 : J1=?737.6, J2=+63.4, J3=?187.6, J4=+124.4, J5=?376.4, J6=?601.2, J7=?657.0, and J8=?800.6 cm?1. Among all the computed J values, six are found to be antiferromagnetic. Four exchange values (J1, J6, J7 and J8) are computed to be extremely strong, with J8, mediated through one μ‐hydroxo and a carboxylate bridge, being by far the largest exchange obtained for any transition‐metal cluster. The origin of these strong interactions is the orientation of the magnetic orbitals in the RuIII centers, and the computed J values are rationalized by using molecular orbital and natural bond order analysis. Detailed NMR studies (1H, 13C, HSQC, NOESY, and TOCSY) of 1 (in CDCl3) confirm the existence of the solid‐state structure in solution. The observation of sharp NMR peaks and spin‐lattice time relaxation (T1 relaxation) experiments support the existence of strong intramolecular antiferromagnetic exchange interactions between the metal centers. A broad absorption peak around 600–1000 nm in the visible to near‐IR region is a characteristic signature of an intracluster charge‐transfer transition. Cyclic voltammetry experiments show that there are three reversible one‐electron redox couples at ?0.865, +0.186, and +1.159 V with respect to the Ag/AgCl reference electrode, which corresponds to two metal‐based one‐electron oxidations and one reduction process. 相似文献
107.
Bicyclo (2.2.2) octanes disposed with β,γ-unsaturated carbonyl chromophore are versatile intermediates for the synthesis of many carbocyclic structures of current interest1. Recently they have also been shown to have great potential towards synthesis of a variety of natural products2. We became interested in acquisition of functionalized annulated bicyclo (2.2.2) octenones of type 1 (Scheme-1) in connection with an exploratory project on the synthesis of polycyclopentanoids. In this context we recently reported that a trapping of a 2, 4-cyclohexadienone with cyclic dienes provides a facile entry into such ring systems3. We now further report an expeditious one step synthesis of annulated bicyclo (2.2.2) octenones 10–15 (Scheme-1) by trapping the 2, 4-cyclohexadienone 3 with various dienophiles 4–9(Scheme-1). 相似文献
108.
Planning time-optimal motions has been a major focus of research in robotics. In this paper we consider the following problem:
given an object in two-dimensional physical space, an initial point, and a final point, plan a time-optimal obstacle-avoiding
motion for this object subject to bounds on the velocity and acceleration of the object. We give the first algorithm which
solves the problem exactly in the case where the velocity and acceleration bounds are given in theL
∞ norm. We further prove the following important results: a tracking lemma and a loop-elimination theorem, both of which are
applicable to the case of arbitrary norms. The latter result implies that, with or without obstacles, a path which intersects
itself can be replaced by one which does not do so and which takes time less than or equal to that taken by the original path.
The work of J. Canny and A. Rege was supported by NSF Grants IRI-89-58577 and IRI-90-14490 and by a David and Lucile Packard
Fellowship. J. Reif's work was supported in part by DARPA/ARO Contract DAAL03-88-K-0185, Air Force Contract AFSOR-87-0386,
ONR Contract N00014-K-0310, and DARPA/ISTO Contract N00014-88-K-0458. 相似文献
109.
110.
We report a novel composite electrode made of chitosan‐SiO2‐multiwall carbon nanotube (CHIT‐SiO2‐MWNT) composite coated on the indium‐tin oxide (ITO) glass substrate. Cholesterol oxidase (ChOx) was covalently immobilized on the CHIT‐SiO2‐MWNT/ITO electrode that resulted in a ChOx/CHIT‐SiO2‐MWNT/ITO cholesterolactive bioelectrode. The CHIT‐SiO2‐MWNT/ITO and ChOx/CHIT‐SiO2‐MWNT/ITO electrodes were characterized with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The influence of various parameters was investigated, including the applied potential, pH of the medium, and the concentration of the enzyme on the performance of the biosensor. The cholesterol bioelectrode exhibited a sensitivity of 3.4 nA/ mgdL?1 with a response time of five seconds. The biosensor using ChOx/CHIT‐SiO2‐MWNT/ITO as the working electrode retained its original response after being stored for six months. The biosensor using ChOx/CHIT‐SiO2‐MWNT/ITO as the working electrode showed a linear current response to the cholesterol concentration in the range of 50–650 mg/dL. 相似文献