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11.
12.
Thomas F. Brodasky 《Journal of separation science》1978,1(5):239-244
Two new acyltetramic acids related to streptolydigin have been isolated from fermentations of Streptomyces lydicus. The principal members of this complex were resolved by TLC on silica gel. However, the methods of detection, permanganate spray or bioautography, were not suitable for both crude fermentation broths and purified extracts. Gas chromatography is unsuitable for the detection of either underivatized or silylated streptolydigins. High performance liquid chromatography (HPLC) particularly on triethylaminoethyl cellulose is rapid and sensitive and is the method of choice for the analysis of both crude and purified samples. Using high performance liquid chromatography, two components were detected in the complex, which are not observed using any of the other chromatographic procedures. 相似文献
13.
The Raman spectra of molten mixtures of Ca(NO3)2\4H2O–KNO3 have been examined, covering the concentration range of 0–70 mole% KNO3. The frequencies in the spectra of the mixtures have been found to change slightly with concentration. Striking variations in the band shapes have been observed in the regions corresponding to the O–H stretching mode (2850–3850 cm–1) and the v4-NO
3
–
mode (700–750 cm–). The results are discussed in terms of perturbed quasi-lattice structure for the melt, in which there could be a displacement of water molecules in the first coordination sphere around Ca2+ by the NO
3
–
ion. 相似文献
14.
在pH5.0的NaOAc-HOAc缓冲溶液中,过量的硝酸银完全沉淀叶酸,用原子吸收光谱法测定剩余的硝酸银,间接计算出叶酸的含量。方法简单快速,回收率在98%~104%之间,相对标准偏差为2.4%。 相似文献
15.
E. V. Gert 《Cellulose (London, England)》1996,3(1):217-228
For preparation of various modified forms of microcrystalline cellulose, an optional combination is proposed of hydrolytic activity with other properties of nitric acid such as, adduct forming ability (manifested as Knecht compound formation), oxidizing, bleaching and nitrating. The manifestation of a chosen acid function is reached by variation of the reaction conditions: concentration, temperature, time, etc. The sole-reagent continuous procedure involving several operations made in a predetermined sequence allows the use of a more simple technological scheme and saves energy, time and materials. The features of transformation of fibrous and microcrystalline forms of native cellulose into cellulose-II through the Knecht compound are discussed. Purely acidic transformation schemes of native cellulose into microcrystalline cellulose hydrate and amorphous low-nitrate powder cellulose according to the above scheme are considered. Morphological features as well as distinguishing properties — enhanced hydrophilicity, sorption activity and degree of whiteness — of the prepared materials are pointed out. The possibility of obtaining uniformly oxidized forms of powder cellulose according to this scheme and the outlook for the use of nitrogen(IV) oxide as a multifunctional reagent are discussed. 相似文献
16.
J. A. Navio M. Macias A. Justo C. Real 《Journal of Thermal Analysis and Calorimetry》1992,38(4):673-682
The thermal decomposition of sodium nitrite or nitrate pre-adsorbed upon TiO2 surfaces has been investigated by employing several techniques as infrared spectroscopy (IR) and temperature programmed desorption in conjunction with mass spectrometry analysis (TPD-MS) to study the features observed during these thermal decompositions. Differential thermal analysis (DTA) in combination with X-ray diffraction analysis (XRD) were used to investigate the possibility of a solid state chemical reaction between the solid products originated from the thermal decomposition of the pre-adsorbed species and the TiO2. On the basis of our results, various characteristic features of these thermal decomposition reactions will be discussed.This work was supported by JUNTA DE ANDALUCIA (financial support for research groups/1990). 相似文献
17.
Gluconacetobacter spp. synthesize a pure form of hydrophilic cellulose that has several industrial specialty applications. Literature reports
have concentrated on intensive investigation of static and agitated culture in liquid media containing high nutrient concentrations
optimized for maximal cellulose production rates. The behavior of these bacteria on semisolid and solid surfaces has not been
specifically addressed. The species Gluconacetobacter hansenii was examined for cellulose synthesis and colony morphology on a range of solid supports, including cotton linters, and on
media thickened with agar, methyl cellulose, or gellan. The concentration and chemical structure of the thickening agent were
found to be directly related to the formation of contiguous cellulose pellicules. Viability of the bacteria following freezer
storage was improved when the bacteria were frozen in their cellulose pellicules.
This article was authored by a contractor of the US government under contract no. DEAC05-00OR22725. Accordingly, the US government
retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others
to do so, for US government purposes. 相似文献
18.
Polyoxometalate (POM) presents great potential in oxidative desulfurization (ODS) reaction. However, the high dissolubility of POM in common solvents makes it difficult to recycle. Besides, the small specific surface area of POM also limits the interaction between them and the substrate. Depositing polyoxometalates onto three-dimensional (3D) network structured materials could largely expand the application of POM. Here, the surfaces of cellulose nanofibrils (CNFs) were modified with very few (3-Aminopropyl) trimethoxysilane (APTS) to endow positive charges on the surfaces of CNFs, and then phosphotungstic acid (PTA) was loaded to obtain the aerogel A-CNF/PTA as the ODS catalyst. FT-IR indicated the successful deposition of PTA onto aminosilane modified CNF surfaces. UV-VIS further suggested the stability of PTA in the aerogels. BET and SEM results suggested the increased specific surface area and the relatively uniform 3D network structure of the prepared aerogels. TGA analysis indicated that the thermal stability of the aerogel A-CNF/PTA50% was a little higher than that of the pure CNF aerogel. Most importantly, the aerogel A-CNF/PTA50% showed good catalytic performance for ODS. Catalysis results showed that the substrate conversion rate of the aerogel A-CNF/PTA50% reached 100% within 120 min at room temperature. Even after five cycles, the substrate conversion rate of the aerogel A-CNF/PTA50% still reached 91.2% during the dynamic catalytic process. This work provides a scalable and facile way to stably deposit POM onto 3D structured materials. 相似文献
19.
20.