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131.
Thin films of poly(vinyl chloride), PVC, and carboxylated poly(vinyl chloride), C-PVC, containing 1.8% of carboxyl groups
were exposed to high energy ultraviolet radiation (λ = 254 nm) in laboratory conditions. The photochemical reactions in irradiated
samples were studied by FTIR and UV–Vis spectroscopy, gel permeation chromatography and gravimetric estimation of insoluble
gel. It was found that photodegradation and photocrosslinking in C-PVC is accelerated, whereas photodehydrochlorination is
retarded comparing to these processes in PVC. Photooxidation investigated on the base of reaction leading to formation of
hydroxyl groups is also more efficient in modified PVC. However, the total amount of carbonyl groups is much lower in UV-irradiated
C-PVC than that in PVC. It indicates that competitive reactions (destruction of carboxyl groups and formation of new carbonyls)
occur simultaneously in C-PVC chains. The influence of carbonyl groups on photochemical processes can be explained by an efficient
Norrish I and II reactions as well as by energy transfer from absorbing species to weak chemical bonds. 相似文献
132.
The chromium content in selected convenience and fast foods was determined. Samples were wet digested with HNO3 (69%) in a microwave digestion system. Chromium was determined by graphite furnace atomic absorption spectroscopy (GF-AAS). The chromium content in convenience food ranged on average from 2.22 to 18.2 μg/100 g, in fast food from 3.76 to 28.6 μg/100 g, and in instant food from 0.34 to 4.75 μg/100 g. 相似文献
133.
Günter Staniek J. Daniel Whittenberger 《Materialwissenschaft und Werkstofftechnik》1980,11(6):197-205
Thermal gradient testing of three oxide dispersion strengthened alloys (two Ni-base alloys, MA 754 and MA 6000E, and the Fe-base MA 956) and the directionally solidified eutectic alloy, γ/γ′-α, have been conducted. Experiments were carried out with maximum temperatures up to 1200°C and thermal gradients on the order of 100°C/mm. The oxide dispersion strengthened alloys were difficult to test because the thermal stresses promoted crack nucleation and growth; thus the ability of these alloys to maintain a thermal gradient may be limited. The stability of individual fibers in γ/γ′-α was found to be excellent; however, microstructural changes were observed in the vicinity of grain boundaries. Similar structures were also observed in isothermally annealed material; therefore thermal gradients do not affect the microstructure of γ/γ′-α in any significant manner. 相似文献
134.
Władysław Mróz Halina Nowakowska 《Chemical Engineering and Processing: Process Intensification》1985,19(6):329-335
An experimental study is described, concerning the influence of the heat flux through a wetted surface of a horizontal tube and of the temperature of a wetting liquid on the minimum liquid flow rate required for complete wetting of the tube. The results are presented in the form of correlating equations. Good agreement was found with the theoretical predictions of Zuber and Staub. 相似文献
135.
Halina Ziembicka 《Cement and Concrete Research》1977,7(3):323-332
This paper presents the results of studies on the effect of micropore structure on the shrinkage of autoclaved cellular concrete with sand aggregate. It has been found that the shrinkage of cellular concrete is the function of volume and specific surface of micropores of radii . On the base of mathematical analysis the requirements concerning the micropore structure of cellular concrete have been proposed to ensure the proper shrinkage characteristic of this material. 相似文献
136.
HalinaHubicka 《中国稀土学报(英文版)》2002,20(1):31-35
The rare earth complexes with EDTA, Ln(edta), show an unusual sequence of affinity for the anion-ex-changers. The sorption and chromatographic separation of y3 for Nd3 complexes with EDTA was studied by using the strongly basic gel and macroporous polyacrylate anion-exchangers, Amberlite IRA 458 and Amberlite 958, and the weakly basic gel polyacrylate anion-exchanger, Amherlite IRA-68. The investigations on sorption and separation of rare earth complexes with EDTA on the polyacrylate anion-exchangers applied mainly in the environment protection so far indicate that they can he applied in anionexchange separation of lanthanide complexes with aminopolycarboxylic acids. It was shown that the weakly basic polyacrylate gel anion-exchanger Amberlite IRA-68 is the most effective in purification of y3 from Nd3 in comparison with the strongly basic anion-exchangers of this type. 相似文献
137.
Ever increasing numbers of aging theories suggest that free radicals are only one factor among others that may initiate stochastic disorders finally terminating life. It is therefore compelling not only to demonstrate the existence of increasing steady-state concentrations of free oxygen radicals during senescence, but it is essential to show that they act in concert with other postulated triggering factors of aging. We have recently shown that various factors may have a life-long influence and challenge oxygen homeostasis of cell respiration. Among these factors are environmental pollutants, therapeutics, and transient hypoxia. Although the nature of these "hits" is different, mitochondrial respiration was found to respond in a similar manner to each of them. The major derangement was an univalent electron leak to oxygen giving rise to the establishment of oxidative stress. Associated with this transformation, oxidative phosphorylation was impaired with the resultant reduction of cellular ATP. Mitochondria from senescent rats exhibited similar alterations of all cell parameters found when adult animals were exposed to "environmental stress" or transient ischemia. Age-related stimulation of mitochondrial oxygen radical generation is therefore suggested to result from accumulation of minihits during life. Based on our data, together with those from other laboratories, it is possible to assess the ranking order of oxygen radicals in the development of stochastic events associated with (or causing) aging. 相似文献
138.
139.
Tomasz Borowski Agnieszka Brojanowska Marcin Kost Halina Garbacz Tadeusz Wierzcho 《Vacuum》2009,83(12):1489-1493
The nickel alloys of the Inconel type (containing above 15wt% of chromium), used in many industrial applications including the manufacture of aircraft, chemistry, power generation, and material processing, have advantageous mechanical properties, high plasticity and good corrosion resistance, but their frictional wear resistance is poor. This drawback can be obviated by subjecting the alloys to various surface treatments.The paper describes the structure and properties of nitrided layers produced on the Inconel 625 nickel alloy (20wt%Cr, 10wt%Mo, 5wt%Fe, 1wt%Co, balance-Ni). It has been found that the diffusion-type chromium nitride layer produced on the alloy surface improves the hardness, frictional wear resistance, fatigue strength and corrosion resistance of the alloy. It was demonstrated that the nitriding process can be successfully used for prolonging the service life of the fiberizing disc intended for the fabrication of what is known as glass wool. 相似文献
140.