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排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Digant Gupta Christopher G Lis Sadie L Dahlk Jessica King Pankaj G Vashi James F Grutsch Carolyn A Lammersfeld 《Nutrition journal》2008,7(1):19
Background
Bioelectrical Impedance (BIA) derived phase angle is increasingly being used as an objective indicator of nutritional status in advanced cancer. Subjective Global Assessment (SGA) is a subjective method of nutritional status. The objective of this study was to investigate the association between BIA derived phase angle and SGA in advanced colorectal cancer. 相似文献82.
Junwei Fu Zhengbiao Zhang Zhenping Cheng Jian Zhu Wei Zhang Xiulin Zhu 《Polymer Bulletin》2008,61(3):287-297
A novel reversible addition-fragmentation chain transfer (RAFT) reagent bearing triphenylamine (TPA)
group, 4-diphenylamino-dithiobenzoic acid benzyl ester (DDABE), was designed and synthesized. It was used
in the RAFT polymerizations of styrene (St) and methyl acrylate (MA) to prepare end-functionalized polymers.
The results of the polymerization showed that the RAFT polymerizations could be well controlled using DDABE
as the RAFT agent. Number-average molecular weight (Mn,GPC) increased linearly
with monomer conversion, and molecular weight distributions were relatively narrow (PDI<
1.50). The results of chain-extension reaction, 1H NMR spectra and UV/Vis
spectra confirmed that most of the polymers chains were end-capped by the functional triphenylamine
(TPA) groups. The effect of feed molar ratios of St/DDABE/AIBN on polymerization was investigated. 相似文献
83.
The cellulose solvent dimethyl sulfoxide (DMSO)/tetrabutylammonium fluoride trihydrate (TBAF) was
successfully applied as reaction medium for the synthesis of allyl cellulose by conversion of the polymer
with allyl chloride in the presence of solid NaOH. Samples with degree of substitution from 0.50 to 2.98
were accessible by varying the molar ratio anhydroglucose unit:allyl chloride:NaOH and reaction time. DMSO/TBAF
was found to be an efficient reaction medium for the preparation of highly functionalized samples from spruce
sulfite pulp with degree of polymerization of about 500 even in a scale of 50 g. The allyl cellulose samples
were characterized by means of FTIR- and NMR spectroscopy. Size exclusion chromatography revealed negligible
polymer degradation during synthesis and purification of the samples. 相似文献
84.
Vanesa Rodríguez-Amor Juan P. Fernández-Blázquez Antonio Bello Ernesto Pérez María L. Cerrada 《Polymer Bulletin》2008,60(1):89-96
Summary The effect of molecular weight on the uniaxial orientation process has been analyzed in two samples of thermotropic poly(diethylene
glycol p,p′-bibenzoate), evaluating the influence of that parameter on the type of orientation obtained. Several strain rates and deformation
temperatures have been tested in order to map out the conditions for obtaining the two different kinds of orientation. The
results show that in the lower molecular weight PDEB sample (Mw=31200) it is rather easy to get exclusively perpendicular “anomalous” orientation, with the molecular axes aligned transversely
to the stretching direction. However, it is extremely difficult to obtain 100% parallel “normal” orientation. On the contrary,
either type of orientation or a mixture of them can be easily developed for the higher molecular weight PDEB sample (Mw=102900). 相似文献
85.
Qingzhao Yao Yuming Zhou Yanqing Sun Xiaoyun Ye 《Journal of Inorganic and Organometallic Polymers and Materials》2008,18(4):477-484
TiO2 hybrid molecular imprinted polymer (MIP) for ethofumesate using methacrylic acid (MAA) as the functional monomer and silane
coupling agent 3-(trimethoxysilyl) propylmethacrylate (KH570) as organic–inorganic connective bridge was synthesized via photo-excitation
method. Hydrogen bond was proved to act between MAA and ethofumesate for pre- and post-polymerization binding properties as
testified by UV spectrometric method. KH570 modified TiO2 nanoparticles were prepared via sonochemical reaction, which can accelerate hydrolysis, increase collision chance for the
reactive system and improve the dispersion of the nanoparticles. Scanning electron microscope (SEM), transmission electron
microscope (TEM), binding and the adsorption kinetics experiments as well as thermogravimetric analysis (TGA) were employed
for characterization. The results indicated that the hybrid MIP revealed a larger surface area and more ordered imprinting
cavities with improved thermal stability compared to organic-only MIP. Furthermore, faster adsorption kinetics and enhancive
adsorption capacity were achieved, which made it promising in chemical sensor applications. 相似文献
86.
Conceptual damage-sensitive features for structural health monitoring: Laboratory and field demonstrations 总被引:2,自引:0,他引:2
F. Necati Catbas Mustafa Gul Jason L. Burkett 《Mechanical Systems and Signal Processing》2008,22(7):1650-1669
The use of damage-sensitive features to evaluate structural condition or health is a very critical aspect of structural health monitoring. The purpose of this paper is to investigate the potential of two different damage-sensitive features for detecting damage. Different damage scenarios are simulated on a large-scale laboratory structure and a three-span highway bridge for demonstration. The features presented in this paper are the modal flexibility-based deflection and curvature both of which are obtained directly from dynamic properties. In the literature, flexibility associated with mode shapes and mode shapes curvatures have been mostly explored. In this study, multi-input–multi-output dynamic data are used to obtain modal flexibility, which is a close approximation to the actual flexibility. A main novelty is that the curvature is calculated from the deflected shapes using the modal flexibility as opposed to using modal vectors. In this paper, the theory of the methodology is explained and then experimental studies and results are presented. For the experimental studies, the laboratory specimen and the three-span bridge were gradually damaged. It is shown that both deflection and curvature are conceptual and physically meaningful features for damage detection and localization. The issues and the requirements for these features to perform successfully are also presented. 相似文献
87.
Application-level performance is a key to the adoption and success of the CDMA 2000. To predict this performance in advance,
a detailed end-to-end simulation model of a CDMA network is built to include application traffic characteristics, network
architecture, network element details using the proposed simulation methodology. We assess the user-perceived application
performance when a RAN and a CN adopt different transport architectures such as ATM and IP. To evaluate the user-perceived
quality of voice service, we compare the end-to-end packet delay for different vocoder schemes such as G.711, G.726 (PCM),
G.726 (ADPCM), and vocoder bypass scheme. By the simulation results, the vocoder bypass scenario shows 30% performance improvement
over the others. We also compare the quality of voice service with and without DPS scheduling scheme. We know that DPS scheme
keep the voice delay bound even if the service traffic is high. For data packet performance, HTTP v.1.1 shows better performance
than that of HTTP v.1.0 due to the pipelining and TCP persistent connection. We may conclude that IP transport technology
is better solution for higher FER environment since the packet overhead of IP is smaller than that of ATM for web browsing
data traffic, while it shows opposite effect to the small size voice packet in RAN architecture. We show that the 3G-1X EV-DO
system gives much better packet delay performance than 3G-1X RTT. The main conclusion is that end-to-end application-level
performance is affected by various elements and layers of the network and thus it must be considered in all phases of the
development process.
Jae-Hyun Kim He received the B.S., M.S., and Ph.D. degrees, all in computer science and engineering, from Hanyang University, Ansan, Korea,
in 1991, 1993, and 1996 respectively. In 1996, he was with the Communication Research Laboratory, Tokyo, Japan, as a Visiting
Scholar. From April 1997 to October 1998, he was a post-doctoral fellow at the department of electrical engineering, University
of California, Los Angeles. From November 1998 to February 2003, he worked as a member of technical staff in Performance Modeling
and QoS management department, Bell laboratories, Lucent Technologies, Holmdel, NJ. He has been with the department of electrical
engineering, Ajou University, Suwon, Korea, as an assistant professor since 2003. His research interests include QoS issues
and cross layer optimization for high-speed wireless communication. Dr. Kim was the recipient of the LGIC Thesis Prize and
Samsung Human-Tech Thesis Prize in 1993 and 1997, respectively. He is a member of the Korean Institute of Communication Sciences
(KICS), Korea Institute of Telematics and Electronis (KITE), Korea Information Science Society (KISS), and IEEE.
Hyun-Jin Lee received the B.S. degree in electrical engineering from Ajou University, Suwon, Korea, in 2004, and is working toward the
M.S. degree and Ph. D. degree in electrical engineering at Ajou University. He has been awarded Samsung Human-Tech Thesis
Prize in 2004. His research interests QoS, especially network optimization and wireless packet scheduling. He is a member
of the KICS.
Sung-Min Oh received the B.S. and M. S. degrees in electrical engineering form Ajou University, Suwon, Korea, in 2004, and is working
toward the Ph. D. degree in electrical engineering at Ajou University. His research interests QoS performance analysis and
4G network. He is a member of the KICS.
Sung-Hyun Cho received his B.S., M.S., and Ph.D. in computer science and engineering from Hanyang University, Korea, in 1995, 1997, and
2001, respectively. From 2001 to 2005, he has been with Samsung Advanced Institute of Technology, where he has been engaged
in the design and standardization of MAC and upper layers of B3G, IEEE 802.16e, and WiBro systems. He is currently a MAC part
leader in the telecommunication R&D center of Samsung Electronics. His research interests include 4G air interface design,
radio resource management, cross layer design, and handoff in wireless systems. 相似文献
88.
Is there a direct relationship between oral astringency and human salivary protein binding? 总被引:1,自引:0,他引:1
For decades, it is believed that astringency is due to the polyphenol-induced complexation of proline-rich salivary proteins
in the oral cavity. In order to compare for the first time the human sensory threshold concentrations and the salivary protein
binding activity of a series of astringent stimuli, human saliva protein was incubated for 5 min at 37 °C in the presence
of astringent food-derived compounds and, after micro-centrifugation, the amount of the target molecules in the supernatant
was quantitatively determined by HPLC-UV/Vis. Significant protein binding was observed for (−)-epigallocatechin-3-gallate,
(−)-gallocatechin-3-gallate, (+)-gallocatechin, and (−)-catechin-3-gallate, all of which containing at least one galloyl moiety
in the molecule and exhibiting rather high sensory thresholds of more than 200 μmol/L. In comparison, (+)-catechin and procyanidin
B2, both lacking in any galloyl function, showed only comparatively low binding activity and, most interestingly, quercetin-3-O-α-l-rhamnopyranosyl-(1 → 6)-β-d-glucopyranoside and 3-carboxymethyl-indole-1-N-β-d-glucopyranoside did not show any protein binding at all, although the later N- and O-glycosides exhibited extraordinarily low sensory threshold concentrations of less than 0.001 and 0.0003 μmol/L, respectively.
The data give some first evidence that the quantity of the non-bound, “free” astringent stimulus in the saliva liquid might
be more closely related to the sensory perception of astringency than the amount complexed or precipitated by proteins. It
is therefore questionable as to whether oral perception of astringency is related to the complexation and/or precipitation
of salivary proteins. 相似文献
89.
A new type of a single-axis azimuthal tracker is presented. The novel feature of this tracker is the ability to move the collector’s plane in two directions through a special support structure. This structure consists of a sliding mechanism on the central axis and a curved window on the cylindrical surface coaxial to the central axis. Consequently, the proposed novel heliotrope behaves similarly to a two-axis tracker. Two different windows designed on the cylindrical surface may be used to provide very high efficiencies throughout a year. Several performance measurements have been conducted on this novel tracker, a polar tracker and the reference two-axis tracker. Pyranometers, appropriately calibrated, were installed on all three systems to record the global incoming irradiance on the collector’s plane. It is shown that the new tracker system can be very efficient since its plane intercepts, at least, 98% of the insolation with respect to a two-axis tracker. The proposed system can be utilized in solar-related applications (photovoltaic or thermal). 相似文献
90.
Jatuporn Wittayakun Pongtanawat Khemthong Sanchai Prayoonpokarach 《Korean Journal of Chemical Engineering》2008,25(4):861-864
Rice husk silica (RHS) in amorphous phase with 98% purity was prepared from a waste rice husk from rice milling by leaching
with hydrochloric acid and calcination. The RHS was used effectively as a silica source for the synthesis of zeolite Y in
sodium form (NaY). The zeolite in pure phase was obtained from a two-step synthetic route in which the starting gels were
mixed, aged for 24 h at room temperature and crystallized for 24 h at 90 °C. The diameter of single crystal particles from
a scanning electron microscope was approximately 1.0 μm, whereas the average particle diameter from laser diffraction particle
size analyzer was approximately 10 μm because of the agglomeration of small crystals. Longer crystallization time in this
route resulted in a mixed phase containing NaY and zeolite P in sodium form (NaP). In addition, a one-step synthetic route
(no aging) was studied and the product was also a mixed phase zeolite. 相似文献