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991.
Hideki Shige Toshitsugu Ishikawa Michio Suzukawa Masato Nishiwaki Takeshi Yamashita Kei Nakajima Toshimitsu Ito Kenji Higashi Makoto Ayaori Atsushi Yonemura Paul Nestel Haruo Nakamura 《Lipids》1998,33(12):1169-1175
The effects of vitamin E on cholesteryl ester (CE) metabolism in 1774 cells were examined. Pretreatment of 1774 cells with
vitamin E at concentrations above 50 μM significantly decreased acetylated low density lipoprotein (LDL)-induced incorporation
of [14C]oleate into CF in cells in a dose-dependent manner. This was partly due to vitamin E Also significantly inhibiting the uptake
of [3H]CE-labeled acetylated LDL by 1774 cells. A trend existed toward suppression of acyl-CoA:cholesterol acyltransferase (ACAT)
activity in the cell lysate at high vitamin E concentration, but there was no effect on hydrolysis of CE. These data indicate
that vitamin E reduces the uptake of modified LDL and suppresses ACAT activity, resulting in less cholesterol esterification
in macrophages; a novel mechanism underlying the antiatherogenic properties of vitamin E. 相似文献
992.
The creep resistance at temperatures between 1200° and 1300°C in air of alumina—SiC-whisker composites was investigated via four-point flexure to examine (1) the effect of whisker content and (2) the influence of densification additives (i.e., Y2 O3 (plus MgO)). The creep resistance of polycrystalline alumina is greatly improved with the addition of ≤ 20 vol% SiC whiskers. The interlocking/pinning of grains by whiskers which limits grain-boundary sliding contributes to the improvement in creep resistance. However, the creep rates of alumina composites in air increase at whisker contents ≥ 30 vol%. Electron microscopy observations suggested that the degradation in creep resistance for whisker content ≥ 30 vol% originated from (1) the promotion of creep cavitation and subsequent microcrack generation from the higher number density of nucleation sites and (2) more extensive formation of grain-boundary amorphous phase(s) associated with an observed increased oxidation rate. Along this one, the excellent creep resistance of alumina composites containing 20 vol% SiC whiskers was significantly degraded by the presence of the intergranular amorphous phases introduced by the addition of the Y2 O3 densification additive. 相似文献
993.
Paul L. Knox 《Cities》1987,4(4)
The Washington metropolitan area is rapidly reaching the point where if can truly be regarded as a ‘world city’: a seat not only of national government but also of national and international corporate headquarters, financial institutions and business services. It has become one of the most prosperous and, in many ways, urbane of US metropolitan areas. At the same time, however, it remains sharply polarized in ethnic, socioeconomic and ecological terms, and its overall development has had to take place within the framework of a uniquely unrepresentative and unresponsive system of government and planning. The city that was founded as a national symbol and a showpiece of planning has become an exemplar of the congested, fragmented and polarized urbanization of advanced capitalism. 相似文献
994.
Lai FY Ort C Gartner C Carter S Prichard J Kirkbride P Bruno R Hall W Eaglesham G Mueller JF 《Water research》2011,45(15):4437-4448
995.
Solving the problem at the source: Controlling Mn release at the sediment-water interface via hypolimnetic oxygenation 总被引:3,自引:0,他引:3
One of the primary goals of hypolimnetic oxygenation systems (HOx) from a drinking water perspective is to suppress sediment-water fluxes of reduced chemical species (e.g., manganese and iron) by replenishing dissolved oxygen (O2) in the hypolimnion. Manganese (Mn) in particular is becoming a serious problem for water treatment on a global scale. While it has been established that HOx can increase sediment O2 uptake rates and subsequently enhance the sediment oxic zone via elevated near-sediment O2 and mixing, the influence of HOx on sediment-water fluxes of chemical species with more complicated redox kinetics like Mn has not been comprehensively evaluated.This study was based on Mn and O2 data collected primarily in-situ to characterize both the sediment and water column in a drinking-water-supply reservoir equipped with an HOx. While diffusive Mn flux out of the sediment was enhanced by HOx operation due to an increased concentration driving force across the sediment-water interface, oxygenation maintained elevated near-sediment and porewater O2 levels that facilitated biogeochemical cycling and subsequent retention of released Mn within the benthic region. Results show that soluble Mn levels in the lower hypolimnion increased substantially when the HOx was turned off for as little as ∼48 h and the upper sediment became anoxic. Turning off the HOx for longer periods (i.e., several weeks) significantly impaired water quality due to sediment Mn release. Continual oxygenation maintained an oxic benthic region sufficient to prevent Mn release to the overlying source water. 相似文献
996.
Collins Adjei Mensah Lauren Andres Paul Baidoo James Kweku Eshun Kwabena Barima Antwi 《Urban Forum》2017,28(2):125-141
The entrenched position now taken by participatory planning in urban planning practice has made the call for community participation in the planning process now higher than ever. Community participation has been well-acknowledged to give local people a voice in planning decisions. This paper assessed the level of participation by local people in the management of urban green spaces. Using a case study research approach, Kumasi city, once the garden city of Africa was selected as the study area. The Kumasi city authorities, and residents including opinion leaders, and officials of allied bodies on green spaces constituted the study’s target population. A blend of qualitative research techniques such as in-depth interviews, focus group discussion, and personal observation was employed whilst theoretical sampling technique was adopted. It was found out that the participation of the local people in the management of green space was low. The local people were neither consulted nor informed on green space projects (parks and gardens) by the city authorities. They were also not empowered to self-facilitate initiatives on green spaces and passively involved in final decisions on green spaces. To correct the situation, it is recommended that features of the communicative planning theory such as dialogue, consensus building, and facilitative leadership should be given attention in the urban planning system of Kumasi especially on green space projects. 相似文献
997.
Mingqiu Wu Johannes G. Khinast Stefan Radl 《American Institute of Chemical Engineers》2018,64(2):437-456
Wet fluidized beds of particles in small periodic domains are simulated using the CFD‐DEM approach. A liquid bridge is formed upon particle‐particle collisions, which then ruptures when the particle separation exceeds a critical distance. The simulations take into account both surface tension and viscous forces due to the liquid bridge. We perform a series of simulations based on different liquid bridge formation models: (1) the static bridge model of Shi and McCarthy, (2) a simple static version of the model of Wu et al., as well as (3) the full dynamic bridge model of Wu et al. We systematically compare the differences caused by different liquid bridge formation models, as well as their sensitivity to system parameters. Finally, we provide recommendations for which systems a dynamic liquid bridge model must be used, and for which application this appears to be less important. © 2017 American Institute of Chemical Engineers AIChE J, 64: 437–456, 2018 相似文献
998.
Michael?J.?HaasEmail author Paul?J.?Michalski Stan?Runyon Alberto?Nunez Karen?M.?Scott 《Journal of the American Oil Chemists' Society》2003,80(1):97-102
Simple alkyl FA esters have numerous uses, including serving as biodiesel, a fuel for compression ignition (diesel) engines.
The use of acid-catalyzed esterification for the synthesis of FAME from acid oil, a by-product of edible vegetable oil refining
that is produced from soapstock, was investigated. Soybean acid oil contained 59.3 wt% FFA, 28.0 wt% TAG, 4.4 wt% DAG, and
less than 1% MAG. Maximum esterification occurred at 65°C and 26 h reaction at a molar ratio of total FA/methanol/sulfuric
acid of 1∶15∶1.5. Residual unreacted species under these conditions, as a fraction of their content in unesterified acid oil,
were FFA, 6.6%; TAG, 5.8%; and DAG, 2.6%. This corresponds to estimated concentrations of FFA, 3.2%; TAG, 1.3%; and DAG, 0.2%,
on a mass basis, in the ester product. In an alternative approach, the acylglycerol species in soapstock were saponified prior
to acidulation. High-acid (HA) acid oil made from this saponified soapstock had an FFA content of 96.2 wt% and no detectable
TAG, DAG, or MAG. Optimal esterification conditions for HA acid oil at 65°C were a mole ratio of FFA/methanol/acid of 1∶1.8∶0.17,
and 14 h incubation. FAME recovery under these conditions was 89% of theoretical, and the residual unesterified FFA content
was approximately 20 mg/g. This was reduced to 3.5 mg/g, below the maximum FFA level allowed for biodiesel, by washing with
NaCl, NaHCO3, and Ca(OH)2 solutions. Alternatively, by subjecting the unwashed ester layer to a second esterification, the FFA level was reduced to
less than 2 mg/g. The acid value of this material exceeded the maximum allowed for biodiesel, but was reduced to an acceptable
value by a brief wash with 0.5 N NaOH. 相似文献
999.
Johannes Z. Mbese 《Journal of Sulfur Chemistry》2014,35(4):438-449
Dithiocarbamate complexes of Zn(II), Cd(II) and Hg(II) were synthesize and characterized by elemental analysis, thermogravimetric analysis, UV–Vis, FTIR, 1H- and 13C-NMR spectroscopy. The complexes were thermolyzed at 180°C to prepare HDA-capped ZnS, CdS and HgS nanoparticles. The optical properties of the nanoparticles showed absorptions that are blue shifted with respect to the bulk and narrow emissions. The ZnS nanoparticles are in the cubic phase with average crystallite sizes of 3–5 nm. The CdS nanoparticles consist of a mixture of cubic and hexagonal phases with particle sizes of 8–22 nm, while the HgS nanoparticles are in the cubic phase with average crystallite sizes of 7–14 nm. 相似文献
1000.