The aluminium (Al) concentration in different brands of beers packaged in Al cans and glass bottles was measured at the end
of the shelf-life of the beer, by the Zeeman graphite furnace atomic absorption spectrophotometry (ZGFAAS) method. The results
show that in all cases a brand of beer packaged in an Al can has a higher Al content than the same brand bottled in glass.
The measurements of the Al concentration in some Al-canned beers throughout 12 months of storage show that a relatively small
increase of the Al concentration in beers occurs throughout storage. All these results indicate that some Al is taken up by
the beer in Al cans, presumably through the slight and slow dissolution of Al from the can wall, due to some defects in the
protective lacquer layer. The evaluated daily intake of Al (0.256 mg) possible through the consumption of beer was practically
negligible in relation to both the total daily dietary Al intake and the tolerable daily Al intake. Thus, beers are an insignificant
source of dietary Al intake and it appears that the Al intake from beers (due to the low content of Al in beers and its low
bioavailability) should not be a cause for concern with regard to Al toxicity for the human body.
Received: 22 April 1996 相似文献
It has long been considered that polar nanoregions in relaxors form at Burns temperature T(d) ≈ 600K. High-temperature dielectric investigations of Pb(Mg(1/3)Nb(2/3)) O(3) (PMN) single crystal, PMN-PbTiO(3) ceramics, and (Pb,La) (Zr,Ti)O(3) ceramics reveal, however, that dielectric dispersion, detected around 600K, is due to the Maxwell-Wagner-type contributions of surface layers. The intrinsic response was analyzed in terms of the universal scaling, taking into account the asymptotic and the correction-to-scaling behavior, and the results imply much higher T(d) or formation of polar nanoregions in a broad temperature range. High values of the dielectric constant indicate, however, that polar order already exists at the highest measured temperatures of 800K. The obtained critical exponents indicate critical behavior associated with universality classes typically found in spin glasses. 相似文献
Gold mining and beneficiation in SW-Bulgaria dates back to antiquity. Investigations of the area have made unique discoveries. Small archaeological gold artifacts (ringlets, wire etc.) of yet unknown age, as well as gold prills and beads from melting, have been found together with native gold. Occasionally, platinumgroup minerals (PGM), e.g. osmium-iridium-rutheniumalloys, are associated with gold and other heavy minerals in placers. The beneficiation of precious metals (panning by gravity separation) also included underground mining of auriferous conglomerates. 相似文献
Process plants should be designed to be economically viable and environmentally friendly, while also being operable and maintainable during process implementation. The safety of processes is among the most important considerations in obtaining results that are more acceptably realistic, as it is linked to the availability and reliability of the process. Inherent safety can effectively be enhanced in the early stages of the design, when the main decisions on process design are made. The aim of this study is to enhance and select the appropriate risk assessment method and to incorporate it into process synthesis, using a mathematical programming approach. A mixed-integer, nonlinear programming (MINLP) model was used for the synthesis of a methanol production process, considering risk assessment during the synthesis. Risk assessment is performed simultaneously with the MINLP process synthesis, where the risk is determined either for the whole process as overall risk, or on a per unitof- a-product basis. For the latter, a new measurement is proposed: the inherent risk footprint. The results of a case study led to two main conclusions: (i) Significantly safer designs can be obtained at negligible economic expense, and (ii) at higher production capacities, a lower inherent risk footprint can be achieved. The results also indicate that designs obtained using this method can have significantly increased inherent safety, while remaining economically viable.
Optimization of shiitake mushroom vacuum drying process was the objective of this research. In order to produce dried sample with satisfactory shelf life, response surface methodology was used. Vacuum drying used to accomplish the task was previously described by the authors. The samples were dried at 46–74 °C and 20–580 mbar. As quality indicators of dried product, total solids, water activity, total phenolics, IC50 and total color change were used. Response surface methodology resulted in optimal conditions of 57.1 °C and 100 mbar. In order to verify predictions and adequacy of the second-order polynomial models, separate validation experiments were conducted at optimum conditions. The predicted amount of total solids was 85.40 %, while aw value was 0.615. 相似文献
This paper presents simultaneous integration of different technologies such as the traditional dry-grind process to obtain ethanol from grain with the gasification of the corn stover followed by either syngas fermentation or catalytic mixed alcohols synthesis. The optimal integrated process when using the entire corn plant (18 kg/s of grain and 10.8 kg/s of stover) is the one in which the dry-grind technology to process corn grain is integrated with the catalytic path for the corn stover due to the improved integration of energy, requiring only 17 MW of energy, 50 MW of cooling and 1.56 gal/gal of freshwater, for an ethanol production cost of 1.22 $/gal. However, the production cost decreases as we only use stover to produce ethanol, while the grain is used for food due to the lower cost of the stover and the more favorable energy balance of the ethanol production process from gasification. 相似文献