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排序方式: 共有145条查询结果,搜索用时 171 毫秒
31.
The synthesis of novel superabsorbent polymers (SAPs) based on itaconic acid (IA) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) is described for application in personal hygiene products such as disposable diapers. The AMPS is introduced to improve the low absorption performance of the existing IA-based SAPs. The salt-resistant properties of AMPS are shown to improve the absorption performance of SAP with respect to aqueous salt solutions. Further, the high ionization constant of the sulfonic acid group of AMPS contributes to the increase of the centrifugation retention capacity (CRC) of the SAP. Meanwhile, the amide group of AMPS improves the gel strength of the SAP by forming hydrogen bonds between the polymer chains. This increase in gel strength is demonstrated by the enhanced absorbency under load (AUL) and rheological analysis. The degree of neutralization affect the absorption properties of SAP, and the SAP exhibits maximum CRC and AUL of 57.3 and 14.4 g/g at 60% neutralization, respectively. As a crosslinking agent content increased, AUL increased but CRC significantly decreased. Additionally, soil pH evaluation confirms that SAP do not cause soil acidification. 相似文献
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O. Roots V. Zitko H. Kiviranta P. Rantakokko P. Ruokojärvi 《Russian Journal of General Chemistry》2010,80(13):2721-2730
Concentrations of polybrominated diphenyl ethers (PBDEs) in Baltic Sea herring Clupea harengus membras L. collected from Estonian coastal waters are reported. In the period 2006–2008 the total PBDE concentrations (ΣPBDE, sum
of 15 congeners) in Baltic herring varied between 0.57 and 4.08 ng g−1 fresh weight. Highest ΣPBDE concentrations were in a 2007 sample from the mouth of the Gulf of Finland and in a 2007 sample
from the Gulf of Riga. The former contained a high concentration of BDE 209 (16.3 ng g−1) and in the latter this congener was the second most abundant. It is not clear whether the BDE 209 concentration in the Gulf
of Finland sample is not an artefact and this value was not included in the above range. The PBDE concentrations increased
with the age of herring are similar to those reported in [1] in fish collected in the Bothnian Sea in 2002 and did not increase
between 2002 and 2008. The majority of concentrations in herring from the Estonian coastal zone was <1.0 ng g−1 fresh weight. The PBDE congener profiles varied regionally as well as with age of the fish. The main congeners were mostly
the BDEs 47, 99, and 100. Some of the variations probably caused by measurement artefacts. 相似文献
34.
Mateović-Rojnik T Frlan R Bogataj M Bukovec P Mrhar A 《Chemical & pharmaceutical bulletin》2005,53(1):143-146
Eudragit RS 100 microspheres containing ketoprofen as a model drug were prepared by the solvent evaporation method using an acetone/liquid paraffin solvent system. The influence of various preparation temperatures: 10, 25, 35, and 40 degrees C, on particle size and morphology, drug content and release kinetics, and drug crystal state was evaluated. With increasing temperature, microsphere average size was found to increase and particle size distribution to widen significantly. At 10 degrees C particles of irregular shape are formed, whereas higher temperatures gradually improve the sphericity of microspheres. As can be seen from SEM photographs, particle surface roughness decreases as preparation temperature increases. It was found that temperature had no effect either on ketoprofen microencapsulation efficiency or on its crystal state, but it does influence emulsion-stabilizer incorporation. Ketoprofen forms solid solution in Eudragit matrix and maintains amorphous state for significant period of time. Drug release rates from microspheres correlated with microspheres' surface roughness and to a lesser extent with particle size. 相似文献
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Byung-Gook Park Dae Hwan Kim Kyung Rok Kim Ki-Whan Song Jong Duk Lee 《Superlattices and Microstructures》2003,34(3-6):231
We have implemented a sidewall spacer patterning method for novel dual-gate single-electron transistor (DGSET) and metal–oxide–semiconductor-based SET (MOSET) based on the uniform SOI wire, using conventional lithography and processing technology. A 30 nm wide silicon quantum wire is defined by a sidewall spacer patterning method, and depletion gates for two tunnel junctions of the DGSET are formed by the doped polycrystalline silicon sidewall. The fabricated DGSET and MOSET show clear single-electron tunneling phenomena at liquid nitrogen temperature and insensitivity of the Coulomb oscillation period to gate bias conditions. On the basis of the phase control capability of the sidewall depletion gates, we have proposed a complementary self-biasing method, which enables the SET/CMOS hybrid multi-valued logic (MVL) to operate perfectly well at high temperature, where the peak-to-valley current ratio of Coulomb oscillation severely decreases. The suggested scheme is evaluated by SPICE simulation with an analytical DGSET model, and it is confirmed that even DGSETs with a large Si island can be utilized efficiently in the multi-valued logic. 相似文献
38.
Ahn JH Jung SH Kim JA Song SB Kwon SJ Kim KR Rhee SD Park SD Lee JM Kim SS Cheon HG 《Chemical & pharmaceutical bulletin》2005,53(8):1048-1050
In the continuation of efforts to modify the structure of our novel DP-IV inhibitors, a series of pyrazolidine derivatives with heteroaryl urea was synthesized and evaluated for their ability to inhibit dipeptidyl peptidase IV (DP-IV). 相似文献
39.
M. A. Lazovskaya S. N. Baranov A. K. Sheinkman A. A. Rok 《Chemistry of Heterocyclic Compounds》1971,7(5):559-560
N-Pyridylethylated derivatives were obtained by the reaction of- or-vinylpyridines with 4-azolidones and their 5-benzylidene-substituted derivatives. Their IR and UV spectra were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 599–600, May, 1971. 相似文献
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