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61.
Metal ion uptake properties of polystyrene-supported chelating polymer resins functionalized with (i) glycine, (ii) hydroxy
benzoic acid, (iii) Schiff base and (iv) diethanol amine have been investigated. The effects of pH, time and initial concentration
on the uptake of metal ions have been studied. The uptake of metal ion depends on pH. The resins are more selective at pH
10 for Pb(II) and Hg(II), whereas at pH 6 they are found to be Cd(II) and Cr(VI) selective. Metal ion uptake properties of
resins follow Freundlich’s equation. The resins are recyclable and are therefore employed for the removal of heavy metal pollutants
from industrial waste water. 相似文献
62.
In many Italian archaeological sites dated between the sixth and third centuries BC, unworked lumps of Cu-based materials are sometimes found, the so called Aes Rude, which according to archaeological considerations were appreciated as currency, as a medium of exchange and as a form of saving. The microchemical investigation of these ancient artefacts discloses their nature as apparently not usable for any functional applications or possible use. Indeed, Aes Rude resemble ordinary copper material, but microchemical results indicate that they are constituted by highly ferruginous leaded copper, making them useless for producing other metal objects by means of casting or hot and cold working. Notwithstanding this intrinsic negative feature, the production of these intractable Cu-based alloys was deliberately carried out to maximise the process yield in terms of produced metal from an impure and unselected metal ore by tailoring the smelting process parameters. With these considerations in mind, the microchemical investigation of these ancient iron–copper alloys gives evidence of the passage from the acceptance of an artefact value based on its true nature or potential use to the acceptance of the value based only on its appearance or form irrespective of its present or future use. This information could contribute to a better understanding of the evolution of human thought and economic and social interactions. 相似文献
63.
合成了多个基于钴氰化锌的双金属氰化络合物(DMC)催化剂,并对催化剂的结晶形态进行了表征.考察了制备过程中,有机配体及其引入方式,温度,搅拌速度对DMC催化剂形态的影响.其中有机配体对DMC催化剂形态的影响是最主要的.有机配体中富电子原子的电负性的强弱和数量共同影响着DMC催化剂的形态.该类原子的电负性越强,得到的DMC催化剂的结晶性越差,无定型部分的比例越高,并且单个原子的电负性强弱比该类原子的数量在此间的影响更大.而在有机配体预先存在的情况下,该沉淀体系则更有利于无定型部分的产生.在30℃左右的沉淀反应温度下,得到的DMC催化剂的无定型部分比例最高.在有机配体存在的情况下,搅拌速度对DMC催化剂形态的影响有限.并且发现存在于有机配体中的DMC催化剂随着时间的推移,形态会发生变化.初步揭示了DMC催化剂的形态与其催化活性间的关系.而无定型态的DMC催化剂更有利于PO的聚合. 相似文献
64.
Historical perspectives for the chemistry of diene complexes of early transition metals developed at Osaka University in the period after 1970s were reviewed briefly and personally. Preparative chemistry of this field commenced from the magnesium-diene 1:1 compounds and quickly extended to almost all the early transition metals. By the studies operated together with other researchers, unique features of these diene complexes, especially their bonding and structure, selective reactions, and catalysis performances are described. 相似文献
65.
ChujiangCai ZhigangShen MingzhuWang ShulinMa YushanXing 《中国颗粒学报》2003,1(4):156-161
This paper reports the use of a colloidal Pd^0 catalysis system to metallize the surface of precipitators separated from coal fly-ash, and metals such as Cu, Ni etc. are deposited on the precipitators surface. Alternatively, according to the characteristic surface of cenospheres, an Ag coating catalysis system is adopted to first deposit Ag on the cenospheres surface, followed, if necessary, by the deposition of other metals such as Cu, Ni, etc. on the Ag coating to produce monolayer and multilayer metal-coated cenospheres. The surface characteristics and the morphologies of the metal coatings are examined in detail with scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) techniques. It can be shown that the quality of metal coatings derived from the Aa coatina catalysis system, is better than that of the colloidal Pd^0 catalysis system. 相似文献
66.
67.
在Brueckner-Hartree-Fock理论框架内, 研究了同位旋非对称核物质中质子和中子单粒子势的动量相关性及其随同位旋非对称度的变化, 在此基础上计算了同位旋对称势, 并讨论了三体核力的影响. 结果表明同位旋对称势对于同位旋非对称度的依赖性很弱, 但对于动量和密度均有较强的依赖性. 当密度固定时, 同位旋对称势随动量增加而减小. 尽管三体核力对于质子和中子单粒子势的动量相关性有较大影响, 但对同位旋对称势的影响很小. 还与目前重离子碰撞输运理论模型中所使用的各种参数化的唯象对称势进行了比较. 相似文献
68.
The performance evaluation of many complex manufacturing, communication and computer systems has been made possible by modeling
them as queueing systems. Many approximations used in queueing theory have been drawn from the behavior of queues in light
and heavy traffic conditions. In this paper, we propose a new approximation technique, which combines the light and heavy
traffic characteristics. This interpolation approximation is based on the theory of multipoint Padé approximation which is
applied at two points: light and heavy traffic. We show how this can be applied for estimating the waiting time moments of
the GI/G/1 queue. The light traffic derivatives of any order can be evaluated using the MacLaurin series analysis procedure. The heavy
traffic limits of the GI/G/1 queue are well known in the literature. Our technique generalizes the previously developed interpolation approximations
and can be used to approximate any order of the waiting time moments. Through numerical examples, we show that the moments
of the steady state waiting time can be estimated with extremely high accuracy under all ranges of traffic intensities using
low orders of the approximant. We also present a framework for the development of simple analytical approximation formulas.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
69.
A novel class of platinum-based initiating systems for the ring-opening polymerization of a wide variety of heterocyclic compounds including epoxides, oxetanes, and 1,3,5-trioxane have been discovered. In addition to a platinum complex as a catalyst, a cocatalyst, consisting of a compound or polymer containing silicon-hydrogen bonds must also be present. This article reports on a preliminary survey of the scope and limitations of these new initiator systems. Particular emphasis in this article has been placed on the ring-opening polymerization of epoxides which have been studied in some detail and which proceed rapidly and exothermically at room temperature. A number of mechanistic studies have been conducted and the best current evidence suggests that polymerization proceeds by a cationic mechanism. Evidence is also presented which suggests that platinum metal colloids may function as the active initiating species. 相似文献
70.
P. Bonville M. Rams K. Królas J.-P. Sanchez P. C. Canfield O. Trovarelli C. Geibel 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(1):77-84
We have examined the magnetic properties of the heavy electron compounds
YbAgGe and YbPtIn by 170Yb M?ssbauer spectroscopy down to 0.1 K, and
the crystal field properties of YbAgGe by Perturbed Angular Correlations
(PAC) measurements up to 900 K. In YbAgGe, we show that each of the two
magnetically ordered phases below 0.8 K involves a specific incommensurate
modulation of the Yb moment. An analysis of existing low temperature specific
heat data suggests the
persistence of fluctuations of the correlated Yb spins down to 0.1 K.
The PAC data allow to discriminate among proposed Yb3+ crystal field
level schemes. In YbPtIn, we show that the low temperature magnetic order
phase has an antiferro-para structure, where zero moment Yb ions coexist with
large moment ones, and that a 90° moment reorientation occurs at
1.4 K. 相似文献