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排序方式: 共有1177条查询结果,搜索用时 797 毫秒
11.
12.
Tomoyuki Koga Shinya Kingetsu Nobuyuki Higashi 《International journal of molecular sciences》2021,22(9)
Self-assembly of artificial peptides has been widely studied for constructing nanostructured materials, with numerous potential applications in the nanobiotechnology field. Herein, we report the synthesis and hierarchical self-assembly of collagen-mimetic peptides (CMPs) bearing various aromatic groups at the N-termini, including 2-naphthyl, 1-naphtyl, anthracenyl, and pyrenyl groups, into nanofibers. The CMPs (R-(GPO)n: n > 4) formed a triple helix structure in water at 4 °C, as confirmed via CD analyses, and their conformations were more stable with increasing hydrophobicity of the terminal aromatic group and peptide chain length. The resulting pre-organized triple helical CMPs showed diverse self-assembly into highly ordered nanofibers, reflecting their slight differences in hydrophobic/hydrophilic balance and configuration of aromatic templates. TEM analysis demonstrated that 2Np-CMPn (n = 6 and 7) and Py-CMP6 provided well-developed natural collagen-like nanofibers and An-CMPn (n = 5–7) self-assembled into rod-like micelle fibers. On the other hand, 2Np-CMP5 and 1Np-CMP6 were unable to form nanofibers under the same conditions. Furthermore, the Py-CMP6 nanofiber was found to encapsulate a guest hydrophobic molecule, Nile red, and exhibited unique emission behavior based on the specific nanostructure. In addition to the ability of CMPs to bind small molecules, their controlled self-assembly enables their versatile utilization in drug delivery and wavelength-conversion nanomaterials. 相似文献
13.
Effects of magnetic field and hydrostatic pressure on martensitic transformations in some ferrous and nonferrous alloys have
been studied. The studies clarified the effects of magnetic field and hydrostatic pressure on martensitic transformation start
temperature, magnetoelastic martensitic transformation, morphology of martensites and transformation kinetics of athermal
and isothermal transformations. That is, transformation start temperatures of all the ferrous alloys examined increase with
increasing magnetic field, but those of non-ferrous, such as Ti-Ni and Cu-Al-Ni shape memory alloys, are not affected. On
the other hand, transformation start temperature decreases with increasing hydrostatic pressure in some ferrous alloys, but
increases in Cu-Al-Ni alloys. The magnetic field and hydrostatic pressure dependences of the martensitic start temperature
are in good agreement with those calculated by the equations proposed by our group. In the work on the Fe-Ni-Co-Ti alloy,
we found that magnetoelastic martensitic transformation appear. In addition, several martensite plates grow nearly parallel
to the direction of applied magnetic field in the specimen of an Fe-Ni alloy single crystal. Moreover, we found that the isothermal
process in an Fe-Ni-Mn alloy changes to the athermal one under magnetic field and the athermal process changes to the isothermal
one under hydrostatic pressure. Based on the facts, a phenomenological theory is constructed, which unifies the two transformation
processes. 相似文献
14.
Nobuhiro Iwasa Tomoyuki Mayanagi Noriaki Ogawa Kentaro Sakata Nobutsune Takezawa 《Catalysis Letters》1998,54(3):119-123
Pd and Pt supported on ZnO, Ga2O3 and In2O3 exhibit high catalytic performance for the steam reforming of methanol, CH3OH+H2OCO2+3HH2, and the dehydrogenation of methanol to HCOOCH3, 2CH3OHHCOOCH3+2HH2. Combined results with temperature-programmed reduction (TPR) and XRD method revealed that Pd–Zn, Pd–Ga, Pd–In, Pt–Zn, Pt–Ga and Pt–In alloys were produced upon reduction. Over the catalysts having the alloy phase, the reactions proceeded selectively, whereas the catalysts having metallic phase exhibited poor selectivities. 相似文献
15.
Physical and gas transport properties of the hyperbranched polyimide prepared from a triamine, 1,3,5-tris(4-aminophenoxy)benzene (TAPOB), and a dianhydride, 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), were investigated and compared with those of linear-type polyimides with similar chemical structures prepared from diamines, 1,4-bis(4-aminophenoxy)benzene (TPEQ) or 1,3-bis(4-aminophenoxy)benzene (TPER), and 6FDA. 6FDA-TAPOB hyperbranched polyimide exhibited a good thermal stability as well as linear-type analogues. Fractional free volume (FFV) value of 6FDA-TAPOB was higher than those of the linear-type analogues, indicating looser packing of molecular chains attributed to the characteristic hyperbranched structure. It was found that increased resistance to the segmental mobility decreases the gas diffusivity of 6FDA-TAPOB, in spite of the higher FFV value. However, 6FDA-TAPOB exhibited considerably high gas solubility, resulting in high gas permeability. It was suggested that low segmental mobility and unique size and distribution of free volume holes arising from the characteristic hyperbranched structure of 6FDA-TAPOB provide effective O2/N2 selectivity. It is concluded that the 6FDA-TAPOB hyperbranched polyimide has relatively high permeability and O2/N2 selectivity, and is expected to apply to a high-performance gas separation membrane. 相似文献
16.
NO
x
reduction with a combination of catalysts, Pd catalyst, NO
x
storage reduction (NSR) catalyst and Cu/ZSM-5 in turn, was investigated to elucidate for the high NO
x
reduction activity of this catalyst combination under oxidative atmosphere with periodic deep rich operation. The catalytic
activity was evaluated using the simulated exhaust gases with periodically fluctuation between oxidative and reductive atmospheres,
and it was found that the NO
x
reduction activity with this catalyst combination was apparently higher than that of the solely accumulation of these individual
activities, which was caused by the additional synergic effect by this combination. The Pd catalyst upstream of the NSR catalyst
improved NO
x
storage ability by NO2 formation under oxidative atmosphere. The stored NO
x
was reduced to NH3 on the NSR catalyst, and the generated NH3 was adsorbed on Cu/ZSM-5 downstream of the NSR catalyst under the reductive atmosphere, and subsequently reacted with NO
x
on the Cu/ZSM-5 under the oxidative atmosphere. 相似文献
17.
Hitoshi Masuda Chiyoshi Kamizawa Kunio Hata Kingo Yokota Tomoo Sakai Mitsuhiro Sato 《Desalination》1978,25(1):89-97
The evaporation drain of sulfite pulp spent liquor contains few volatile fatty acids, most of which is acetic acid. The main objective of this study is to recover acetic acid as the concentrated solution (about 4%), which could be used as a culture medium of the yeast. As acetic acid can easily pass through the cellulose acetate membrane, SP drains neutralized by NaOH, NH4OH and Ca(OH)2 were used as the feed solutions. In all cases, concentration by reverse osmosis was successfully carried out provided the appropriate pretreatment was employed. The recovery of acetic acid was 95.6, 90.5 and 98.2% for Na-, NH4-, and Ca-drain, respectively. In addition, the recovered (permeated) water may be used as an industrial one. 相似文献
18.
Meso-porous Al2O3-supported Ni catalysts exhibited the highest activity, stability and excellent coke-resistance ability for CH4 reforming with CO2 among several oxide-supported Ni catalysts (meso-porous Al2O3 (Yas1-2, Yas3-8), -Al2O3, -Al2O3, SiO2, MgO, La2O3, CeO2 and ZrO2). The properties of deposited carbons depended on the properties of the supports, and on the meso-porous Al2O3-supported Ni catalyst, only the intermediate carbon of the reforming reaction formed. XRD and H2-TPR analysis found that mainly spinel NiAl2O4 formed in meso-porous Al2O3 and -Al2O3-supported catalysts, while only NiO was detected in -Al2O3, SiO2, CeO2, La2O3 and ZrO2 supports. The strong interaction between Ni and meso-porous Al2O3 improved the dispersion of Ni, retarded its sintering and improved the activated adsorption of CO2. The coking reaction via CH4 temperature-programed decomposition indicated that meso-porous Al2O3-supported Ni catalysts were less active for carbon formation by CH4 decomposition than Ni/-Al2O3 and Ni/-Al2O3. 相似文献
19.
H. Yokota 《应用聚合物科学杂志》1985,30(1):263-277
The mechanism of cellulose alkalization in isopropyl alcohol (IPA)–water–sodium hydroxide system was studied from the viewpoint of the selective distribution of sodium hydroxide between cellulose and the medium, and of the lattice transition of cellulose. A mixture of IPA, water, and sodium hydroxide spontaneously separates into two layers, i.e., the upper layer solution (ULS) consists of IPA, water, and a small amount of sodium hydroxide and the lower one (LLS) consists of sodium hydroxide, water, and a very small quantity of IPA. The role of the ULS and the LLS was distinctive. The ULS has a function to distribute sodium hydroxide with water in cellulose uniformly according to the distribution equilibrium between ULS and cellulose, and the ULS recovers sodium hydroxide with water from the LLS as the distribution equilibrium shifts in the alkalization of cellulose. The concentration of sodium hydroxide in the LLS and that of IPA in the ULS exerts an influence on the lattice structure of alkali cellulose. During the transformation from cellulose I to alkali cellulose, decrystallization does not occur. Some portion of alkali cellulose reverted to cellulose I by regeneration. 相似文献
20.
Sarawut Rimdusit Wanpen Benjapan Suttichai Assabumrungrat Tsutomu Takeichi Rikio Yokota 《Polymer Engineering and Science》2007,47(4):489-498
Surface segregation in polymer blend systems between 3,3′,4,4′‐biphenyltetracarboxylic dianhydride/4,4′‐diaminodiphenyl ether (s‐BPDA/ODA) polyimide and block copolymer based on polysiloxane‐block‐polyimide (SPI) has been investigated. These polyimide blends, having various compositions of the SPI, were processed by a solution casting method. The glass substrate used in the film‐casting process shows significant effect on the migration of surface segregated species to enrich the air‐exposed surface, whereas the more polar s‐BPDA/ODA tends to remain close to the polar glass substrate. X‐ray photoelectron spectroscopy reveals that even at low SPI concentration, the siloxane moieties in the block copolymer tend to segregate into the air side surface. Contact angle measurement evidently indicates an enrichment of the hydrophobic siloxane fraction on the blend film surface. The average water contact angle of glass side surface is 77°C whereas that of the air side is about 102°C in every blend ratio. This behavior confirms the surface segregation phase separation in these polymer blends. Finally, the surface morphology observed by atomic force microscopy also suggests segregation type of phase separation in these blend systems. POLYM. ENG. SCI., 47:489–498, 2007. © 2007 Society of Plastics Engineers. 相似文献