Relationship of iso‐α‐acid content and endogenous antioxidative potential during storage of lager beer

One of the critical issues regarding the quality of beer is the change in its chemical composition that occurs during storage. Decomposition of iso‐α‐acids results in an undesirable decrease in bitterness as well as a deterioration in the sensory profile of the beer. These changes are caused by the susceptibility of iso‐α‐acids to degradation owing to the influence of reactive oxygen species and light. The aim of this study was to investigate the influence of storage conditions (temperature, light) on the degradation of iso‐α‐acids during aging, with the main focus on monitoring the relationship between the turnover of iso‐α‐acids, the sulphur dioxide content and the antioxidative potential of stored beer as measured by electron spin resonance spectroscopy. In agreement with previous investigations, a significant decrease in the content of bitter compounds (up to 18 % relative to the original level, depending on storage conditions) was observed. A significant decrease in the antioxidant potential of beer was recorded simultaneously and the data confirmed a strong correlation between these parameters. The decline in beer bitterness could become a marker for estimating oxidative damage during storage. Copyright © 2014 The Institute of Brewing & Distilling     

A transport model considering charge adsorption inside pores to describe salts rejection by nanofiltration membranes

In the present work, rejection of mineral salts by nanofiltration membranes is modeled by a new knowledge model considering a charge distribution along the membrane pores. The model is classically based upon the coupling between the extended Nernst–Planck equation of transport within the pores with the Donnan, steric and dielectric interfacial exclusion. In literature, this kind of model is currently being used to describe salt rejections and it requires assessment of the membrane charge density and the dielectric constant of the solution inside the pores or the dielectric constant of the membrane material. Experimental estimation of these parameters, especially the membrane charge density, is difficult. For this reason, these parameters are usually adjusted so as to fit experimental rejections. The novelty of the proposed approach lies with the membrane charge density, which is not considered constant along the pores. Indeed, in this work, the membrane charge density was introduced in the model by means of adsorption isotherms, which were determined beforehand from the streaming potential measurements. In this case, only the dielectric constant inside pores had to be adjusted. The good agreement found between experimental and simulated rejection curves with coherent dielectric constants proves that the model theory is consistent. It has also proved that the estimated membrane charge density was, clearly, not overestimated as it was previously reported and made it possible to foresee a fully predictive model.     

Effect of surface roughness and surface modification of indium tin oxide electrode on its potential response to tryptophan

The effect of surface modification of indium tin oxide (ITO) electrode on its potential response to tryptophan was investigated for ITO substrates with different surface roughness. It was found that a small difference in surface roughness, between ∼1 and ∼2 nm of R_a evaluated by atomic force microscopy, affects the rest potential of ITO electrode in the electrolyte. A slight difference in In:Sn ratio at the near surface of the ITO substrates, measured by angle-resolved X-ray photoelectron spectrometry and Auger electron spectroscopy is remarkable, and considered to relate with surface roughness. Interestingly, successive modification of the ITO surface with aminopropylsilane and disuccinimidyl suberate, of which essentiality to the potential response to indole compounds we previously reported, improved the stability of the rest potential and enabled the electrodes to respond to tryptophan in case of specimens with R_a values ranging between ∼2 and ∼3 nm but not for those with R_a of ∼1 nm. It was suggested that there are optimum values of effective work function of ITO for specific potential response to tryptophan, which can be obtained by the successive modification of ITO surface.     

文23气田气井无阻流量确定方法研究

针对文23气田开发中后期现场多采用一点法简易试气方法确定井（层）产能的实际情况，统计分析了44井次多点产能试井资料数据，利用二项式基本关系式和无因次压力和无因次产量的相关性分析，推导出了适合文23气田应用的一点法计算无阻流量的经验公式。生产应用表明，本文方法获得的无阻流量更为合理，对实际应用具有重要的指导意义。     

Effect of concrete carbonation process on the passivating products of galvanized steel reinforcements

The composition of passivating products on galvanized steel reinforcement in concrete during carbonation was studied. Cube‐shaped concrete specimens were manufactured with Portland 52.5 R cement and reinforced with hot‐dip galvanized steel sheets obtained from pure Zn and Zn? Sn? Bi? Ni alloy bath. The concrete specimens were exposed to air curing for 28 days and then to the carbonation chamber. Corrosion rate and potential measurements were performed both during the curing in air and exposure in a carbonation chamber. At defined periods of time, some concrete specimens were broken and the galvanized steel sheets were submitted to XRD, SEM observations and EDX analysis. The growth of the passivation products was evaluated by integrating the diffraction peaks. XRD analysis and SEM observations show that the layer of calcium hydroxyzincate (CaHZn), formed on the galvanized sheets during the air curing, is destroyed by the concrete carbonation process. However, potential measurements indicate that the galvanized steel always remains in the passive state. X‐ray diffractometry was not able to identify the new passivating product; EDX maps suggest the presence of zinc carbonates.     

SULFUR FILTER BY INTERMETALLIC MEDIA

ABSTRACT

Two types of filter are developed. One is for the removal of sulfur compounds in petroleum and its derived products. The other is for upgrading, which is to lower the amount of asphaltene. Although research in selectivity and life cycle estimation of intermetallic media is still continuing, the mechanisms behind this technology are based upon the concept of nanotechnology and the principle of membrane mimetic chemistry.     

Tribocorrosion behaviour of TiCxOy thin films in bio-fluids

Decorative coatings require not only an attractive appearance for market applications, but also an ability to protect the surface underneath. Because of this, corrosion, wear and their combined effects (termed tribocorrosion) are particularly important for lifetime prediction. In this paper, the tribocorrosion behaviour of a range of single layered titanium oxycarbide, TiC_xO_y, coatings, produced by DC reactive magnetron sputtering, has been studied and reported as a function of electrode potential and applied load. The study was conducted in a reciprocating sliding tribo-system (Plint TE 67/E) in a bio-fluid (an artificial perspiration solution) at room temperature. During the wear tests, both the open-circuit potential and the corrosion current were monitored. The results showed that electrode potential and load have a significant influence on the total material loss. The variations in R_p (polarization resistance) and C_f (capacitance) before and after sliding, obtained by Electrochemical Impedance Spectroscopy (EIS) were evaluated in order to provide an understanding of the resistance of the film in such conditions. Tribocorrosion maps were generated, based on the results, indicating the change in mechanisms of the tribological and corrosion parameters for such coatings, as a function of load and applied potential.     

Coarse-graining the electrostatic potential via distributed multipole expansions

Multipole expansions offer a natural path to coarse-graining the electrostatic potential. However, the validity of the expansion is restricted to regions outside a spherical enclosure of the distribution of charge and, therefore, not suitable for most applications that demand accurate representation at arbitrary positions around the molecule. We propose and demonstrate a distributed multipole expansion approach that resolves this limitation. We also provide a practical algorithm for the computational implementation of this approach. The method allows the partitioning of the charge distribution into subsystems so that the multipole expansion of each component of the partition, and therefore of their superposition, is valid outside an enclosing surface of the molecule of arbitrary shape. The complexity of the resulting coarse-grained model of electrostatic potential is dictated by the area of the molecular surface and therefore, for a typical three-dimensional molecule, it scale as N2/3 with N, the number of charges in the system. This makes the method especially useful for coarse-grained studies of biological systems consisting of many large macromolecules provided that the configuration of the individual molecules can be approximated as fixed.     

Antioxidant and antiglycation properties of Passiflora alata and Passiflora edulis extracts

The leaves of Passiflora alata Dryander and Passiflora edulis Sims, traditionally used in American countries to treat both anxiety and nervousness by folk medicine, are rich in polyphenols, which have been reported as natural antioxidants. In this study, the antioxidant activities of P. edulis and P. alata hydroalcoholic leaf extracts were verified in in vitro and ex vivo assays. P. alata showed a higher total reactive antioxidant potential than did P. edulis. The antioxidant activities of both extracts were significantly correlated with polyphenol contents. In addition, both extracts attenuated ex vivo iron-induced cell death, quantified by lactate dehydrogenase leakage, and effectively protected against protein damage induced by iron and glucose. These findings demonstrate that the P. alata and P. edulis leaf extracts have potent in vitro and ex vivo antioxidant properties and might be considered as possible new sources of natural antioxidants.     

丽水、椒江凹陷油气潜力分析和勘探突破口的选择

本文利用第四轮对外合作勘探成果分析台北坳陷丽水、椒江凹陷具有中国东部裂陷盆地的基本地质特征.下古新统优质烃源岩、丰富的油气资源和众多的圈闭是“九五”勘探的主战场.丽水凹陷已发现好的油气显示,是实现勘探突破的最现实地区,椒江凹陷勘探程度低是勘探的后备地区.以灵峰组为区域盖层的下古新统成油组合是主要勘探目的层.丽水西斜坡和分隔丽水东西次凹的灵峰低潜山构造带是该区最有利的两个区带,缓坡近凹构造是实现勘探突破的首选目标.文中指出了该区勘探的复杂性及相应的措施.