排序方式: 共有31条查询结果,搜索用时 15 毫秒
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用自由基溶液降合方法制备一系列苯乙烯-丙烯酸甲酯线型共聚物,用核磁共振测定了苯基在共聚物中的百分比,在该共聚物的四氢呋喃溶液中,用三氟乙酸汞在共聚物的苯环上进行亲电取代反应,得到可溶性汞化共聚物,由于这类泵化共的可溶于四氢呋喃,二氯甲烷等溶剂,用重沉淀法多次提纯,得到了纯度很高,溶解性较好的含重金属二价汞的共聚物,用红外光谱仪测定共聚物上的汞基团,用原子吸收定量测试共聚中的汞的百分聚代率,结果表明 相似文献
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L.M. da Silva M.C. de Melo A.N. Medina F.G. Gandra 《Physica B: Condensed Matter》2009,404(19):3018-3020
We report on results of X-ray powder diffraction, magnetization and specific heat measurements of the pseudo-ternary (Ce1−xLax)PdIn2 system with x=0; 0.2; 0.4 and 0.6. The results show a linear increase of the unit cell volume and a reduction of the ferromagnetic transition as La content increases. The Debye temperature, Sommerfeld coefficient and crystal field parameters were estimated from specific heat data, and are found to be weakly dependent of the Ce concentration. Also, the variation of magnetic entropy at TC is only weakly dependent on x (ΔS≅0.92Rln2) indicating that TK/TC is approximately constant along the series. The TC and TK behaviors are explained by the variation of the exchange parameter due to the volume change when Ce is replaced by La. Our results indicate that the chemical pressure is the dominant effect rather than the chemical disorder for determining the physical proprieties of the (Ce1−xLax)PdIn2 system. 相似文献
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A. Magnus G. Carvalho F. Garcia P.J. von Ranke G.D. Loula A.A. Coelho F.C.G. Gandra 《Journal of magnetism and magnetic materials》2009,321(19):3014-3018
In this work, we report the theoretical and experimental investigations on the magnetic and magnetocaloric properties for Gd0.5Pr0.5Al2 compound in different magnetic fields. The magnetization features indicate that Gd0.5Pr0.5Al2 is ferrimagnetic at low temperatures. We also present data from X-ray magnetic circular dichroism (XMCD) experiments for this compound, with which we have confirmed that the magnetic moments of the Pr ions are antiparallel to the magnetic moments of the Gd ions. The magnetocaloric parameters, ΔTS and ΔST, were obtained from calorimetric data and both curves present normal and inverse magnetocaloric effect. A theoretical model for ferrimagnetic coupling, including the crystalline electrical field anisotropy, was used to describe the ΔTS and ΔST experimental results. 相似文献
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Naveen Gandra Onica Le Gendre David Aebisher K.N. Houk Ruomei Gao 《Tetrahedron》2006,62(46):10771-10776
We suggest that singlet molecular oxygen [1O2 (1Δg)] is formed upon irradiation of indigo 1 [in air or O2-saturated DMSO and DMSO (0.5% H2SO4)] and indigo carmine 2 [in air or O2-saturated CH3OH, D2O, and 1-butyl-3-methylimidazolium tetrafluoroborate (BmIm-BF4)]. The quantum yield for production of 1O2 is estimated to be 0.6 for 1 and 0.3-0.5 for 2. The rates of reaction of 1O2 with 1 and 2 were determined by monitoring the emission of 1O2 at 1270 nm over time. Low molar absorptivities (at 532 nm) and rapid physical quenching caused by 1 and 2 limit their utility as 1O2 photosensitizers in solution. Compounds 1 and 2 degrade slowly during the photolysis due to a self-sensitized (type I or II) photooxidation reaction. Oxidative cleavage of 1 by singlet oxygen and superoxide, and 2 by superoxide has been noted before (Kuramoto, N.; Kitao, T. J. Soc. Dyers Color. 1979, 95, 257-261; Kettle, A. J.; Clark, B. M.; Winterbourn, C. C. J. Biol. Chem. 2004, 279, 18521-18525). 相似文献
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Polyhach Y Bordignon E Tschaggelar R Gandra S Godt A Jeschke G 《Physical chemistry chemical physics : PCCP》2012,14(30):10762-10773
Measurement of distances with the Double Electron-Electron Resonance (DEER) experiment at X-band frequencies using a pair of nitroxides as spin labels is a popular biophysical tool for studying function-related conformational dynamics of proteins. The technique is intrinsically highly precise and can potentially access the range from 1.5 to 6-10 nm. However, DEER performance drops strongly when relaxation rates of the nitroxide spin labels are high and available material quantities are low, which is usually the case for membrane proteins reconstituted into liposomes. This leads to elevated noise levels, very long measurement times, reduced precision, and a decrease of the longest accessible distances. Here we quantify the performance improvement that can be achieved at Q-band frequencies (34.5 GHz) using a high-power spectrometer. More than an order of magnitude gain in sensitivity is obtained with a homebuilt setup equipped with a 150 W TWT amplifier by using oversized samples. The broadband excitation enabled by the high power ensures that orientation selection can be suppressed in most cases, which facilitates extraction of distance distributions. By varying pulse lengths, Q-band DEER can be switched between orientationally non-selective and selective regimes. Because of suppression of nuclear modulations from matrix protons and deuterons, analysis of the Q-band data is greatly simplified, particularly in cases of very small DEER modulation depth due to low binding affinity between proteins forming a complex or low labelling efficiency. Finally, we demonstrate that a commercial Q-band spectrometer can be readily adjusted to the high-power operation. 相似文献
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Two-Photon-Induced CO-Releasing Molecules as Molecular Logic Systems in Solution,Polymers, and Cells
Dr. Vadde Ramu Dr. Gandra Upendar Reddy Dr. Jingjing Liu Patrick Hoffmann Dr. Rudrakant Sollapur Dr. Ralf Wyrwa Dr. Stephan Kupfer Prof. Dr. Christian Spielmann Dr. Sylvestre Bonnet Prof. Dr. Ute Neugebauer Dr. Alexander Schiller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(36):8453-8458
Phototherapeutic applications of carbon monoxide (CO)-releasing molecules are limited because they require harmful UV and blue light for activation. We describe two-photon excitation with NIR light (800 nm)-induced CO-release from two MnI tricarbonyl complexes bearing 1,8-naphthalimide units ( 1 , 2 ). Complex 2 behaves as a logic OR gate in solution, nonwovens, and in HeLa cells. CO release, indicated by fluorescence enhancement, was detected in solution, nonwoven, and HeLa cells by single- (405 nm) and two-photon (800 nm) excitation. The photophysical properties of 1 and 2 have been measured and supported by DFT and TDDFT quantum chemical calculations. Both photoCORMs are stable in the dark in solution and noncytotoxic, leading to promising applications as phototherapeutics with NIR light. 相似文献
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