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101.
Savina IN English CJ Whitby RL Zheng Y Leistner A Mikhalovsky SV Cundy AB 《Journal of hazardous materials》2011,192(3):1002-1008
Novel nanocomposite materials where iron nanoparticles are embedded into the walls of a macroporous polymer were produced and their efficiency for the removal of As(III) from aqueous media was studied. Nanocomposite gels containing α-Fe2O3 and Fe3O4 nanoparticles were prepared by cryopolymerisation resulting in a monolithic structure with large interconnected pores up to 100 μm in diameter and possessing a high permeability (ca. 3 × 10−3 m s−1). The nanocomposite devices showed excellent capability for the removal of trace concentrations of As(III) from solution, with a total capacity of up to 3 mg As/g of nanoparticles. The leaching of iron was minimal and the device could operate in a pH range 3-9 without diminishing removal efficiency. The effect of competing ions such as SO42− and PO43− was negligible. The macroporous composites can be easily configured into a variety of shapes and structures and the polymer matrix can be selected from a variety of monomers, offering high potential as flexible metal cation remediation devices. 相似文献
102.
Lara Naurath Christoph Weidner Thomas R. Rüde Andre Banning 《Mine Water and the Environment》2011,30(3):231-236
Sodium fluorescein (uranine) is one of the most popular fluorescent dyes for tracer experiments due to its chemical properties,
low detection limits and low costs. As a limiting factor, it is generally assumed that Na-fluorescein cannot be properly detected
under acid conditions because of weak fluorescence intensities at the standard excitation wavelength (490 nm). This laboratory
study introduces a method to quantify Na-fluorescein in low pH waters without having to raise pH to alkaline conditions, which
spares the time- and cost-intensive filtration of hydroxide precipitates prior to analysis. It was applied for recovery tests
in water samples from five mining sites in Germany. These were buffered to pH 1.5 where Na-fluorescein shows a second fluorescence
intensity maximum at an excitation wavelength of 438 nm. The method had satisfying recovery rates although, as expected, a
higher detection limit compared to standard wavelength and pH. High Fe contents in the waters are a limiting factor—the impact
of increasing Fe concentrations at a constant dye spike was evaluated and yielded a distinct negative trend between Fe and
detected Na-fluorescein, probably due to Fe-fluorescein complexation. However, good recovery can be expected in mine waters
with up to ≈100 mg L−1 Fe. The method of standard addition offers a potential calculative solution for higher Fe concentrations, resulting in significantly
better Na-fluorescein recovery rates, compared to direct measurements. The method introduced here represents a promising approach
for improving Na-fluorescein applicability in acid environments. 相似文献
103.
Development of nano-composite lead-free electronic solders 总被引:1,自引:0,他引:1
Inert, hybrid inorganic/organic, nano-structured chemicals can be incorporated into low melting metallic materials, such as
lead-free electronic solders, to achieve desired levels of service performance. The nano-structured materials technology of
polyhedral oligomeric silsesquioxanes (POSS), with appropriate organic groups, can produce suitable means to promote bonding
between nano-reinforcements and the metallic matrix. The microstructures of lead-free solder reinforced with surface-active
POSS tri-silanols were evaluated using scanning electron microscopy (SEM). Wettability of POSS-containing lead-free solders
to copper substrate was also examined. Steady-state deformation of solder joints made of eutectic Sn-Ag solder containing
varying weight fractions of POSS of different chemical moieties were evaluated at different temperatures (25°C, 100°C, and
150°C) using a rheometric solids analyzer (RSA-III). Mechanical properties such as shear stress versus simple shear-strain
relationships, peak shear stress as a function of rate of simple shear strain, and testing temperature for such nano-composite
solders are reported. The service reliability of joints made with these newly formulated nano-composite solders was evaluated
using a realistic thermomechanical fatigue (TMF) test profile. Evolution of microstructures and residual mechanical property
after different extents of TMF cycles were evaluated and compared with joints made of standard, unreinforced eutectic Sn-Ag
solder. 相似文献
104.
105.
Ghinwa Naja Bohumil Volesky Andre Schnell 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2006,81(4):648-658
A specially designed bioreactor including an axial microfilter for cell retention was evaluated for continuous‐flow operation with selected liquid media as controls and in aerobic cultivations of Saccharomyces yeasts. In the initial tests, performance characteristics such as filtration rates and cell accumulation were assessed as a function of filter rotational speed, operating pressure, cultivation time and microfilter type (i.e. membrane or porous metal). The bioreactor did not perform satisfactorily when viscous extracellular polymer was present in the liquid. In the continuous‐flow culture enabling cell retention, Saccharomyces cerevisiae yeast cell concentrations were enhanced by as much as 16‐fold over ordinary batch growth. Concomitant filtration rates were stable over operating times of up to 130 h and hence were independent of the cell concentration. The maximum steady‐state flux was enhanced at rotational speeds up to 400‐700 rpm ranging from 22 to 42 L m?2 h?1. Higher rotation rates offered no further improvements. The maximum stabilized flux was independent of operating pressure. Pressure increases caused momentary flux improvements, which rapidly declined and eventually restabilized. Copyright © 2006 Society of Chemical Industry 相似文献
106.
O Vanhooteghem W Courtens J Andre U Sass M Song 《Canadian Metallurgical Quarterly》1998,15(5):374-377
Hermansky-Pudlak syndrome is a rare, inherited, autosomal recessive disease. Diagnosis is based on a triad of signs: oculocutaneous albinism, a hemorrhagic tendency due to a platelet disorder, and an accumulation of lipopigments in different organs, particularly the medullary macrophages. We describe a child with the characteristic findings of this syndrome, which often goes unrecognized because of the discrete nature of the cutaneous and hemorrhagic manifestations. This diagnosis is important because of the risk not only of hemorrhage but also of granulomatous colitis and long-term pulmonary fibrosis. 相似文献
107.
Administered a modified version of a Piagetian test on the concept of relative velocity (including questions on the duration of relative displacements) to 96 children placed in age groups of 7, 9, 11, and 13 yr. It was found that (a) the developmental stages of the concept were comparable to those observed by Piaget except for formal operations which seem to evolve later; (b) the combination of 2 movements of same direction but unequal velocity is more difficult to synthesize than any other; (c) success on the problem of durations is not a prerequisite of at least partial success on the problem of velocities; and (d) complete success on the problem of velocities is not necessarily verbalized in spatio-temporal terms. To explain the difficulty observed in synthesizing velocities, the importance of the instructions (e.g., specifying the speed of each mobile) and of changes in the spatial order of the mobiles was emphasized. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
108.
This paper intends firstly to present how digital switching was introduced into the French network nearly ten years ago and what are the main advantages brought by digital switching systems. Various cases in the network such as trunk or local exchanges are examined; general as well as particular advantages are shown. Secondly, the technical requirements for these exchanges are described; an emphasis is put on the specific aspects of digital switching. Digital switching systems already in operation or on the verge of being commissioned are outlined. Finally, different tables give information concerning mainly the number of subscriber lines connected to class 3 and 4 digital exchanges by the end of 1978. 相似文献
109.
110.
Andre Abad 《Microscopy research and technique》1988,8(2):217-222
To prevent section wrinkles usually encountered with the use of coated single-hole grids, a simple method was developed. Formvar film resting on a platform with holes (3.5 mm diameter) was heated with a slide warmer (60–65°C). The bottom of a glass petri dish was inverted over the platform to keep the ambient air at the desired temperature. Sections were picked up from the boat of the diamond knife with a single-hole grid and deposited at the orifice of the platform and allowed to dry. The grids were then carefully pushed through the orifice of the platform with the blunt head of a nail (3 mm diameter). 相似文献