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81.
This Review discusses the synthesis and characterization by our Group of new antibiotics belonging to the class of penicillins, cephalosporins and rifamycins with ferrocenyl and 1, 1′-ferrocenilene residues in the molecule. As reactants for 6-aminopenicillanic acid (6-APA) and 7-aminocephalosporanic acid (7-ACA) the following were used: 1, 1-bis(chlorocarbonyl)ferrocene, ferrocenyl sulfochloride, 1, 1′-ferrocenylenedisulfochloride and thioglycolic acids S-modified with ferrocene. In the synthesis of rifamycins, the hydrazides of the thioglycolic acids, S-modified with ferrocene, were employed as nucleophilic agents. The synthesized intermediates were characterized by elemental analysis, TLC, IR, UV and 1H NMR spectra. The characterization of new antibiotics was made by TLC, IR and UV spectral analysis. Biological activity was tested on Gram-negative and Gram-positive bacteria. Good activity is reported towards Gram-positive bacteria in the case of derivatives containing residues of thioglycolic acid S-modified with ferrocene, the antibacterial activity being similar to that of amoxicillin, carbenicillin and cephalothin. All compounds are inactive towards Gram-negative bacteria. 相似文献
82.
Electric fields of the anions, cations and neutral forms of 2-aminopurine and 6-thioguanine have been mapped. Certain important
features of the maps are similar to those found earlier in the neutral and ionic forms of adenine and guanine. The computed
electric field patterns satisfactorily explain reactive sites and biological activity of the molecules. 相似文献
83.
84.
Polyethyleneimine (PEIM) samples crosslinked by a commercial epoxy resin (Epon 828) were prepared, and their adsorption capacity for acidic gases was studied. The swelling and deswelling characteristics of the crosslinked samples were also examined as part of this program. Reactivation of these adsorbents could be carried out by heat, or by a combination of heat and treatment in dilute alkalies. 相似文献
85.
J. M. Pico C. P. Menaut J. Fernández J. L. Legido M. I. Paz Andrade 《Journal of solution chemistry》1991,20(1):115-124
Excess molar enthalpies hE at 25 and 35° C and atmospheric pressure, are reported for the binary mixtures formed by a 2-butanone and 2-pentanone with 1-chlorobutane, 1-chloropentane, 1-chlorohexane, or 1-chlorooctane. The hE values for all the mixtures are positive, increasing as the 1-chloroalkane length increases and as the ketone length decreases. Excess molar enthalpies depend slightly on the temperature. The experimental values together with those from the literature were used to calculate the interaction parameters for the Dang-Tassios version of the UNIFAC model.Communicated at the Festsymposium celebrating Dr. Henry V. Kehiaian's 60th birthday, Clermont-Ferrand, France, 17–18 May 1990. 相似文献
86.
阐述了紫外无机非线性光学晶体分子工程学探索方法的基本特点,具体分析深紫外无机非线性光学晶体硼铍酸锶(SBBO)以氟硼铍酸钾(KBBF)为主要参考晶体的分子设计方法,随后根据晶体结构研究、单晶培养、和非线性光学性能测定等实验结果讨论SBBO作为新型深紫外无机晶体的主要优点,即它既具有更短的紫外吸收边(接近155nm)和较大的非线性光学系数(d22(SBBO)=06×d22(BBO)=138pm/V),同时晶体无明显层状习性,并肯有良好的化学稳定性和机械性能 相似文献
87.
测量了Cr^4+,YAG、Cr^4+,Mg2SiO4晶体在室温和液氮温度下的荧光光谱,吸收光谱和激发态寿命,讨论了温度变化时,两种晶体中Cr^4+近红外辐射积分强度变化与激光发态寿命变化的关系,得出结论:在77K ̄300K范围内,Cr^4+的^3T2能级荧光辐射截面本身受温度影响不大,Cr^4+辐射荧光的变化,主要是由无辐射弛豫速率随温度变化而引起的。 相似文献
88.
89.
Thermal, spectroscopic and electrical properties of lead pyrophosphate glass prepared by melt quenching have been examined.
A model based on the structural disproportionation of the P2O
7
4−
ions has been proposed and is shown to consistently explain all the observations. The equilibrium of various anionic species
has been discussed on the basis of their electronegativities which are in turn related to their basicities.
Communication No. 129 from the Materials Research Centre 相似文献
90.
A diagnostic study q (energy transfer processes in a He-N2 flowing discharge and afterglow has been performed in a radiofrequency-produced plasma cooled in a liquid nitrogen hath. Optical emission spectroscopy in the visible and infrared spectral range as well as Langrnuir probe diagnostics were used. The vibrational kinetics of CO injected in such an afterglow has been examined. It shows a slow cooling of the electrons in the afterglow regime. The electron kinetics responsible joy CO vibrahonal excitation is turned off when N2 is added to the He discharge, while that for vibrationally excited N2 molecules is turned on. The results are discussed on the basis of previous theorerical calculations and experiments on the He-N2 system. 相似文献