Aging of surfactant modified titanium gels

Titanium hydrogels prepared without and with different amounts of surfactant (sodium dodecylbenzene sulfonate) have been examined for their behavior during aging for more than 100 days (some for more than 200 days) at different temperatures. By means of XRD semi-quantitative analyses and SEM observations with high magnification (100 K), the effects of the surfactant on the crystalline structure and content, on the morphology and the size of the particles, and on the aggregation phenomena have been investigated. It was also found that aging somewhat decreases the adsorption capacity of the gels.     

Physical mechanism of the electrical polarization of polyethylene terephthalate

The relation between the structural and dynamical properties of amorphous and partially crystalline polyethylene terephthalate and its electret properties was analyzed. The thermal stability of polarization charges and space charges was found to increase with aging in the glassy state and with increasing degree of crystallinity. The discharge behavior was governed by the interaction of real charges and polarization charges. The combination of different charging techniques resulted in a linear superposition of the respective discharge processes on heating.     

Constraint on linear, spatiotemporally nonlocal, spatiotemporally nonhomogeneous constitutive relations

The structure of modern electromagnetic theory imposes a fundamental constraint on the constitutive relations which describe linear material media. Here, in extension to previous work, we provide a proof of this algebraic constraint for the most general type of linear medium: one that is bianisotropic and spatiotemporally nonhomogeneous as well as spatiotemporally nonlocal.     

老化P507萃取剂再生研究

研究了用试剂R12再生老化P507萃取剂工艺，讨论了R12用量、反应时间对再生P507萃取剂可见光谱、萃取稀土分相时间、P507收率的影响。本方法在生产实践中业已取得成功。实验和应用结果表明，再生P507萃取剂与新配剂P507萃取剂在萃取分离稀土性能上无明显差异和变化。本方法简单易行、成本低廉、实用可靠。     

Performance comparisons for maintained items

Most maintenance studies deal with the problem of maintenance-costs optimization, given the cost of the available maintenance actions and a cost objective function. The focus in this paper is on yet another relevant aspect namely the improvement in performance that results from a maintenance action in terms of performance criteria of interest. The evaluation of performance improvement requires comparisons of random quantities which is done by means of suitable probabilistic ordering notions. Different modelling situations are considered, and for each of them conditions are obtained on the life distributions of the present item, and the new one if of different type, that ensure performance improvement. Apart from providing a decision tool for maintenance application, the paper also contributes to clarifying relationships between (probabilistic) ordering notions and aging properties within the maintenance context.     

Glottic Characteristics and Voice Complaint in the Elderly

This study evaluated the relationship between voice complaint and deviant vocal fold status with special regard to presbylarynx, in patients aged more than 60 years, with pharyngeal-laryngeal complaint. The material consisted of clinical histories and images obtained by laryngoscopies from protocols from the Larynx Institute-INLAR, Sao Paulo, Brazil, of 210 patients, 88 men and 122 women, aged more than 60 years, who had sought otorhinolaryngologic treatment. Indicative glottic characteristics of the presbylarynx, such as vocal fold bowing, prominence of vocal processes, and spindle-shaped glottic chink, were analyzed. The increase in mass, leukoplakia, and other vocal fold alterations, distinct from these two, grouped as miscellaneous, as well as the presence or absence of voice complaint were also analyzed. Vocal fold bowing, prominence of vocal processes, and spindle-shaped glottic chink showed a strong correlation among each other. The presence of presbylarynx was accompanied by less voice complaint than the presence of vocal fold mucosa alterations, which in turn are more common where an absence of presbylarynx exists.     

新型高温合金C-286热处理工艺探讨

介绍了一种新型铁基高温合金C_2 86,经过不同的固溶处理及时效工艺 ,获得了细小弥散的球形γ′相 ;随着时效时间的延长 ,γ′相长大并向 η相转变 ;此合金具有优良的抗氧化性和耐蚀性。     

Crosslinking poly[1-(trimethylsilyl)-1-propyne] and its effect on physical stability

Poly[1-(trimethylsilyl)-1-propyne] (PTMSP) has been crosslinked using 3,3′-diazidodiphenylsulfone to improve its solvent resistance and physical stability. This study reports the influence of crosslinking on N₂, O₂ and CH₄ gas permeabilities and fractional free volume (FFV) as a function of time. Crosslinking PTMSP renders it insoluble even in excellent solvents for the uncrosslinked polymer. The gas permeability and FFV of uncrosslinked and crosslinked PTMSP decreased over time, so crosslinking PTMSP does not arrest physical aging. The addition of 10 wt.% polysiloxysilsesquioxanes (POSS) nanoparticles decreased the permeability of PTMSP by 55%, and the permeability and FFV values were stable over time for PTMSP films containing 10 wt.% POSS nanoparticles. The permeability of PTMSP at a given FFV was greater than that of other substituted polyacetylenes, polysulfones or polycarbonates, which is consistent with differences in the arrangement of free volume in these polymers, as probed by positron annihilation lifetime spectroscopy (PALS). Ellipsometry was used to characterize physical aging of thin (400 nm) uncrosslinked and crosslinked PTMSP films supported on silicon wafers. The ellipsometry results showed that crosslinking does not markedly slow physical aging of thin PTMSP films.     

Aging mechanisms of oil-in-water emulsions based on a bioemulsifier produced by Yarrowia lipolytica

The aging mechanisms of oil-in-water emulsions prepared with Yansan, a bioemulsifier produced by a Brazilian wild strain of Yarrowia lipolytica, IMUFRJ 50682, in glucose-based fermentation medium, were studied and compared with those prepared with Gum Arabic. Oil-in-water emulsions obtained by combining three different organic phases, perfluoro-n-hexane, n-hexadecane and toluene, with two aqueous buffers of different pH, and two bioemulsifiers, were studied through the evolution of the mean droplet size. The emulsions were prepared by sonication and their droplet size distribution was followed for 60 days at 301 K using image analysis. The results indicate that the aging mechanisms of the studied emulsions depend mainly on the bioemulsifier and on the pH of the medium. It is shown that the emulsions containing Gum Arabic age by coalescence while Yansan-based emulsions change their aging mechanisms from coalescence at pH 3 to molecular diffusion at pH 7.     

Influence of polyvinylpyrrolidone (PVP) on alumina sols prepared by a modified Yoldas procedure

Al₁₃ polycations containing alumina sols, prepared by a modified Yoldas procedure were mixed with polyvinylpyrrolidone (PVP). Although Al speciation in freshly prepared sols was not affected by PVP addition the decay rate of Al₁₃ polycations was slightly decreased in PVP-containing sols. PVP does not show any influence on particle size and particle growth. The influence of PVP addition on viscosity and flow behavior of modified Yoldas sols depends on their solids content and molar ratio.