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排序方式: 共有568条查询结果,搜索用时 359 毫秒
61.
Four new partially fluorinated metal organic frameworks (HF-MOFs) have been synthesized under different solvothermal conditions (H(2)O or dimethylformamide (DMF)) from transition metal cations [Co(2+) and Mn(2+)], 3-methyl pyridine (3-mepy) and 4,4'-(hexafluoroisopropylidene) bis(benzoic acid) (C(17)H(10)F(6)O(4), H(2)hfbba), to determine the influence of reaction conditions on the formation of MOFs. This family of materials displays a striking degree of structural similarity depending on the solvent of synthesis. HF-MOFs synthesized from H(2)O [Co-HFMOF-W, Co(hfbba)(3-mepy)(H(2)O) and Mn-HFMOF-W, Mn(hfbba)(3-mepy)(H(2)O)] contain three-dimensional connectivity whereas HF-MOFs synthesized from DMF Co-HFMOF-D, [Co(2)(hfbba)(2)(3-mepy)(2)]·(DMF)(3) and Mn-HFMOF-D, [Mn(2)(hfbba)(2)(3-mepy)]·(H(2)O) are two-dimensional in nature. Co-HFMOF-W and Mn-HFMOF-W are iso-structural polymeric materials. Thermal gravimetric analysis performed on as-synthesized HF-MOFs revealed that these compounds have high thermal stability (~350 °C). The continuous decrease of the χT product with decreasing T for Co-HFMOF-D and Co-HFMOF-W respectively indicates the presence of antiferromagnetic exchange interaction between two Co(2+) (S = 3/2) metal centers within a cluster. 相似文献
62.
Peptide nucleic acids containing 2-pyrimidinone (P) and 3-oxo-2,3-dihydropyridazine (E) heterocycles recognized C-G and U-A inversions in a polypurine tract of double helical RNA with high affinity and sequence selectivity at pH 6.25. E-modified PNA bound strongly to bacterial A-site RNA, while no binding was observed to the human A-site RNA. 相似文献
63.
Singh P Kumar P Kumari K Sharma P Mozumdar S Chandra R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(2):909-912
In the present work, we report a novel method for the synthesis of palladium and lead nanoparticles by the reduction method in tetrazolium ring based ionic liquid. Palladium and lead nanoparticles so-prepared were well characterized by powder X-ray diffraction measurements (pXRD), transmission electron microscopy (TEM) and quasi elastic light scattering (QELS) techniques. Powder X-ray diffraction (pXRD) analysis revealed all relevant Bragg's reflection for crystal structure of palladium and lead. Powder X-ray diffraction plots also revealed no oxidized material of palladium and lead nanoparticles. TEM showed nearly uniform distribution of the particles in methanol and confirmed by QELS. Typical applications of palladium nanoparticles include in vitro use and sensor design applications. Palladium nanoparticles is also ideal for spin coating, self-assembly and monolayer formation. Palladium nanoparticles can also be considered as potential new catalysts. 相似文献
64.
Bhattacharjee CR Goswami P Pramanik HA Paul PC Mondal P 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(5):1408-1415
Two new mixed-ligand iron(III) complexes, [Fe(L(n))(acac)(C(2)H(5)OH)] incorporating coordinated ethanol from the reaction solvent were accessed from the reaction of [Fe(acac)(3)] with [ONO] donor dibasic tridentate unsymmetrical Schiff base ligands derived from condensation of 2-hydroxy-1-napthaldehyde with 2-aminophenol (H(2)L(1)) or 2-aminobenzoic acid (H(2)L(2)). The thermal study (TGA-DTA) provided evidence for weakly bound ethanol which is readily substituted by neutral N-donor molecule imidazole, benzimidazole or pyridine to produce an array of newer complexes, [Fe(L(n))(acac)X] (n=1, 2; X=Im, Bim, Py). The compounds were characterized by elemental analyses, FT-IR, UV-vis, solution electrical conductivity, FAB mass, (1)H and (13)C NMR spectroscopy. Room temperature magnetic susceptibility measurements (μ(eff)~5.8 B.M.) are consistent with spin-free octahedral iron(III) complexes. Cyclic voltammetry of ethanol complexes revealed a quasi-reversible one electron redox response (ΔE(p)>100 mV) for the Fe(III)/Fe(II) couple. Low half wave redox potential (E(1/2)) values suggested easy redox susceptibility. The ground state geometries of the ethanol and imidazole complexes have been ascertained to be distorted octahedral by density functional theory using DMol3 program at BLYP/DNP level. 相似文献
65.
66.
Pardasani D Tak V Purohit AK Kanaujia PK Dubey DK 《European journal of mass spectrometry (Chichester, England)》2011,17(1):57-64
Gas chromatography-mass spectrometry (GC-MS) analysis of O,O'-dialkyl methylphosphonites (DAMPs) was carried out with a view to developing a database and understanding the mechanism of fragmentation. DAMPs are included in the list of schedule 2B4 chemicals of the Chemical Weapons Convention. GC-MS analysis of DAMPs and their deuterated analogs revealed that their fragmentations were dominated by α-cleavages, alkenyl radical loss and hydrogen rearrangements. Based on fragment ions of deuterated analogs and density functional theory calculations, the fragmentation routes were rationalized. 相似文献
67.
Gupta S Pandotra P Ram G Anand R Gupta AP Husain K Bedi YS Mallavarapu GR 《Natural product communications》2011,6(1):93-96
The chemical composition of the essential oil from the rhizome of ginger (Zingiber officinale Roscoe), collected from Nahan, Himachal Pradesh, India, was determined by gas chromatography and GC-MS. Fifty-one compounds, representing 95.1% of the oil, were identified. The oil was characterized by relatively large amounts of the monoterpenoids 1,8-cineole (10.9%), linalool (4.8%), borneol (5.6%), alpha-terpineol (3.6%), neral (8.1%), geraniol (14.5%), geranial (9.5%), trans-dimethoxy citral (5.0%) and geranyl acetate (6.3%). Five compounds, namely trans-linalool oxide, trans-linalool oxide acetate, (Z)-dimethoxycitral, (E)-dimethoxy citral and epi-zingiberenol are reported for the first time in oil of ginger. 相似文献
68.
Gautam Pankaj Sahu Daya Ram Dixit Avinash Som Tanmoy 《Journal of Optimization Theory and Applications》2021,190(2):491-523
Journal of Optimization Theory and Applications - In this paper, the first-order forward–backward–half forward dynamical systems associated with the inclusion problem consisting of... 相似文献
69.
We have used Ramakrishnan–Yussouff (RY) density functional theory (DFT) to explore the topology of the phase diagram of two-component charge stabilised colloidal suspensions confined to a two-dimensional plane. The particles of the system interact via purely repulsive soft core Yukawa potential. Pair correlation functions (PCFs) used as input informations in DFT were calculated by solving both the hypernetted chain (HNC) and Percus–Yevick (PY) integral equation theories. To test the relative performance of the HNC and PY theories in the context of phase transitions, we have also studied the corresponding one-component systems. We found that RY DFT with HNC PCFs does not stabilise solid in both the one- and two-component cases, whereas the PY theory does. By considering the freezing into the substitutionally disordered triangular solid, we found that the temperature-composition phase diagrams of the binary mixture are narrow spindles whose thickness depends on the symmetry of the mixture components and the value of the screening constant of the Yukawa potential. Although the phase diagram obtained by RY DFT with structural inputs calculated by the PY theory is found to be shifted to higher temperature region in the temperature-composition plane, however, it captures qualitatively all the essential features of the phase diagram. Our results are in principle verifiable through computer simulations and experiments. 相似文献
70.
R. Andrew Sims Pankaj Kadwani Heike Ebendorff-Heideprem Lawrence Shah Tanya M. Monro Martin Richardson 《Applied physics. B, Lasers and optics》2013,111(2):299-304
We report femtosecond pulse generation and chirped pulse amplification in Tm:fiber. A mode-locked oscillator operating in the soliton regime produced 800 fs pulses with 5 nm spectral bandwidth, at 40 pJ pulse energy. This oscillator seeded a pre-amplifier that utilizes a Raman soliton self-frequency shift to produce wavelength tunable pulses with 3 nJ energy, reduced pulse duration of 150 fs, and increased bandwidth of 30 nm. For further amplification, the pulses were stretched up to 160 ps using a chirped Bragg grating (CBG). Stretched pulses were amplified to 85 nJ after compression in single-mode Tm:fiber and recompressed with the CBG as short as 400 fs. Compressed pulses were coupled into a highly nonlinear tellurite fiber to investigate the potential of this ultrashort pulse 2-μm fiber source as a pump for mid-IR supercontinuum generation. 相似文献