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21.
Transport of surface-modified iron nanoparticle in porous media and application to arsenic(III) remediation 总被引:1,自引:0,他引:1
Sushil Raj Kanel Dhriti Nepal Bruce Manning Heechul Choi 《Journal of nanoparticle research》2007,9(5):725-735
The surface-modified iron nanoparticles (S-INP) were synthesized, characterized and tested for the remediation of arsenite
(As(III)), a well known toxic groundwater contaminant of concern. The S-INP material was fully dispersed in the aqueous phase
with a particle size distribution of 2–10 nm estimated from high-resolution transmission electron microscopy (HR-TEM). X-ray
photoelectron spectroscopy (XPS) revealed that an Fe(III) oxide surface film was present on S-INP in addition to the bulk
zero-valent Fe0 oxidation state. Transport of S-INP through porous media packed in 10 cm length column showed particle breakthroughs of 22.1,
47.4 and 60 pore volumes in glass beads, unbaked sand, and baked sand, respectively. Un-modified INP was immobile and aggregated
on porous media surfaces in the column inlet area. Results using S-INP pretreated 10 cm sand-packed columns containing ∼2 g
of S-INP showed that 100 % of As(III) was removed from influent solutions (flow rate 1.8 mL min−1) containing 0.2, 0.5 and 1.0 mg L−1 As(III) for 9, 7 and 4 days providing 23.3, 20.7 and 10.4 L of arsenic free water, respectively. In addition, it was found
that 100% of As(III) in 0.5 mg/L solution (flow rate 1.8 mL min−1) was removed by S-INP pretreated 50 cm sand packed column containing 12 g of S-INP for more than 2.5 months providing 194.4
L of arsenic free water. Field emission scanning electron microscopy (FE-SEM) showed S-INP had transformed to elongated, rod-like
shaped corrosion product particles after reaction with As(III) in the presence of sand. These results suggest that S-INP has
great potential to be used as a mobile, injectable reactive material for in-situ sandy groundwater aquifer treatment of As(III). 相似文献
22.
S. D. Gunapala S. V. Bandara J. K. Liu S. B. Rafol J. M. Mumolo C. A. Shott R. Jones J. Woolaway II J. M. Fastenau A. K. Liu M. Jhabvala K. K. Choi 《Infrared Physics & Technology》2003,44(5-6):411-425
A 9 μm cutoff 640 × 512 pixel hand-held quantum well infrared photodetector (QWIP) camera has been demonstrated with excellent imagery. A noise equivalent differential temperature (NEDT) of 10.6 mK is expected at a 65 K operating temperature with f/2 optics at a 300 K background. This focal plane array has shown background limited performance at a 72 K operating temperature with the same optics and background conditions. In this paper, we discuss the development of this very sensitive long-wavelength infrared camera based on a GaAs/AlGaAs QWIP focal plane array and its performance in quantum efficiency, NEDT, uniformity, and operability. In the second section of this paper, we discuss the first demonstration of a monolithic spatially separated four-band 640 × 512 pixel QWIP focal plane array and its performance. The four spectral bands cover 4–5.5, 8.5–10, 10–12, and 13.5–15 μm spectral regions with 640 × 128 pixels in each band. In the last section, we discuss the array performance of a 640 × 512 pixel broad-band (10–16 μm full-width at half-maximum) QWIP focal plane. 相似文献
23.
Proton relaxation times in human red bone marrow by volume selective magnetic resonance spectroscopy
F. Schick H. Bongers W. -I. Jung B. Eismann M. Skalej H. Einsele O. Lutz C. Claussen 《Applied magnetic resonance》1992,3(6):947-963
In hematological diseases the composition of red bone marrow shows alterations. The relaxation timesT 1 andT 2 of water and lipids in human hemopoietic bone marrow of 14 normal volunteers and 10 patients with acute leukemia and bone marrow carcinosis are determined using a double spin echo spectroscopy sequencein vivo. The volumes of interest (VOI) of (13 mm)3 in the center of vertebral bodies are examined using different measurement parameters. ForT 1 measurements an inversion-recovery method is used.T 2 is evaluated from spectra with differentTE. T 1 (water) is found in a range between 1000 and 1700 ms,T 1 (lipids) in a range between 260 and 320 ms in healthy volunteers.T 2 (water) is determined between 32 and 65 ms. In some cases phase distortions of the water signals occur in the spectra. Water flow within the VOI may be a possible reason.T 2 (lipids) is evaluated between 73 and 91 ms. The patients with acute leukemia exhibit clearly reduced lipid signals in their spectra. Lipid relaxation times could not be determined in these cases.T 2 (water) is prolonged in acute leukemia to 51–98 ms.T 1 (water) was not significantly different from values of healthy volunteers in our measurements. Results are discussed in comparison to relaxometric data from imaging and STEAM spectroscopic methods of other authors. 相似文献
24.
Joo J.H. Choi J.J. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2004,32(6):2263-2264
A new type of microwave amplifier module, consisting of a solid-state amplifier, a predistortion linearizer, and a traveling-wave-tube (TWT), is realized. Measurements show a noise figure of 2.2 dB at 9.5 GHz and the third-order intermodulation distortion ratio of 53 dBc at 10 dB back off from P1 dB point. 相似文献
25.
Dong Hwan Choi Yoshio Katakura Rieko Matsuda Yuzuru Hayashi Masato Hirobe Yasuhiro Goda Kazuaki Ninomiya Suteaki Shioya 《Analytical sciences》2007,23(2):215-218
The mathematical model for predicting the precision, limit of detection (LOD) and range of quantitation (ROQ) in a competitive enzyme-linked immunosorbent assay (ELISA) proposed by Hayashi et al. (Anal. Chem., 2004, 76, 1295) was validated. The model describes the relative standard deviation (RSD) of concentration estimates by the RSDs of pipetting volumes of analyte, enzyme-conjugated antigen, antibody and substrate solutions, and the standard deviation (SD) of inherent absorbances between the wells in an ELISA plate. For 6 kinds of direct competitive ELISA kits, the LOD and ROQ predicted by the model agreed well with those obtained by experiments with real samples. It was also confirmed that the model is applicable to the prediction of uncertainty that depends on the pipetting error of the viscous antiserum solution. The model was demonstrated to be useful for estimating the LOD and ROQ of competitive ELISA. 相似文献
26.
Ju Yeon Woo Eun Hee Kim Byung Kyu Kim 《Journal of polymer science. Part A, Polymer chemistry》2007,45(23):5590-5596
Doping of conductive fullerene particles to the formulation of conventional holographic polymer dispersed liquid crystal‐induced dual effects of reducing both droplet coalescence and operating voltage. Fullerene induced an induction period which otherwise does not exist, followed by a gradual increase of diffraction efficiency to a saturation value being increased with increasing fullerene content. The increased diffraction efficiency was caused by the decreased droplet coalescence which was due to the hindered migration of LC by the fullerene particles. On the other hand, doped fullerene particles augmented the conductivity of polymer phase and hence the local electrical field imposed on LC droplet, which overcome the threshold for driving and reduced operating voltage and response times. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5590–5596, 2007 相似文献
27.
28.
C.X. Gao F.C. Yu S.Y. Jeong A.R. Choi P. Parchinskiy D.J. Kim H.J. Kim Y.E. Ihm C.G. Kim C.S. Kim 《Journal of magnetism and magnetic materials》2006
GaMnN and Be-codoped GaMnN were grown via molecular beam epitaxy using a single GaN precursor and their structural and magnetic properties were examined. X-ray diffraction and superconducting quantum interference device (SQUID) measurements revealed that the grown layers are homogeneous without precipitates. The saturation magnetization of GaMnN has increased from ∼4 to ∼16 emu/cm3 via codoping of Be. The d–d exchange interaction between Mn atoms was discussed for the ferromagnetism of GaMnN. 相似文献
29.
Oil migration in filled chocolates limits shelf life due to texture changes and loss of visual appeal. Spatial and temporal
oil concentration changes of a two-layer chocolate and peanut butter filling system, which models a filled chocolate, were
monitored by magnetic resonance imaging. Formulations of chocolate varied with respect to particle size, milk fat content
and emulsifier level. Sorption-time experimental data was used to establish the best fit diffusion coefficient for a Fickian
diffusion model. On the basis of the comparison of spatial experimental data to the model, Fickian diffusion alone does not
account for oil migration.
Authors' address: Michael J. McCarthy, Department of Food Science and Technology, University of California, One Shields Avenue,
Davis, CA 95616, USA 相似文献
30.
We study the large-sample properties of a class of parametric mixture models with covariates for competing risks. The models allow general distributions for the survival times and incorporate the idea of long-term survivors. Asymptotic results are obtained under a commonly assumed independent censoring mechanism and some modest regularity conditions on the survival distributions. The existence, consistency, and asymptotic normality of maximum likelihood estimators for the parameters of the model are rigorously derived under general sufficient conditions. Specific conditions for particular models can be derived from the general conditions for ready check. In addition, a likelihood-ratio statistic is proposed to test various hypotheses of practical interest, and its asymptotic distribution is provided. 相似文献