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61.
62.

A series of polyacrylate‐polystyrene‐polyisobutylene‐polystyrene‐polyacrylate (X‐PS‐PIB‐PS‐X) pentablock terpolymers (X=poly(methyl acrylate) (PMA), poly(butyl acrylate) (PBA), or poly(methyl methacrylate) (PMMA)) was prepared from poly (styrene‐b‐isobutylene‐b‐styrene) (PS‐PIB‐PS) block copolymers (BCPs) using either a Cu(I)Cl/1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) or Cu(I)Cl/tris[2‐(dimethylamino)ethyl]amine (Me6TREN) catalyst system. The PS‐PIB‐PS BCPs were prepared by quasiliving carbocationic polymerization of isobutylene using a difunctional initiator, followed by the sequential addition of styrene, and were used as macroinitiators for the atom transfer radical polymerization (ATRP) of methyl acrylate (MA), n‐butyl acrylate (BA), or methyl methacrylate (MMA). The ATRP of MA and BA proceeded in a controlled fashion using either a Cu(I)Cl/PMDETA or Cu(I)Cl/Me6TREN catalyst system, as evidenced by a linear increase in molecular weight with conversion and low PDIs. The polymerization of MMA was less controlled. 1H‐NMR spectroscopy was used to elucidate pentablock copolymer structure and composition. The thermal stabilities of the pentablock copolymers were slightly less than the PS‐PIB‐PS macroinitiators due to the presence of polyacrylate or polymethacrylate outer block segments. DSC analysis of the pentablock copolymers showed a plurality of glass transition temperatures, indicating a phase separated material.  相似文献   
63.
The crystallisation kinetics of experimental glasses in 3 different systems: (A) Li2O–SiO2, (B) Li2O–Al2O3–SiO2 and (C) Li2O–K2O–Al2O3–SiO2 were studied under non-isothermal conditions. The DTA results revealed a stronger tendency to crystallisation of binary compositions in comparison to the ternary and quaternary compositions comprising Al2O3 and K2O which present the lower crystallisation, i.e. the crystallisation propensity follows the trend A > B > C. The devitrification process in the Li2O–SiO2 and Li2O–Al2O3–SiO2 systems began earlier and the rate was higher in comparison to that of glasses in the quaternary Li2O–K2O–Al2O3–SiO2 system. Thus, addition of Al2O3 and K2O to glasses of Li2O–SiO2 system was demonstrated to promote glass stability against crystallisation. However, the activation energy for crystallisation was shown to depend also on the SiO2/Li2O ratio with the binary system showing a decreasing trend with increasing SiO2/Li2O ratio, while the opposite tendency was being observed for compositions with added Al2O3 and K2O.  相似文献   
64.
In the last few years, silver nanoparticles have been proposed as a promising alternative for the label-free detection of proteins via metal-enhanced fluorescence. Generally, the aromatic amino acid tryptophan is most frequently used in this type of studies, because the intrinsic fluorescence of proteins is usually dominated by tryptophan emissions. In the present study, we evaluated the fluorescence behavior of tryptophan in the presence of a silver colloid with nanoparticles of 100 nm in diameter. The results showed that a nanoparticles concentration of 32 mg L?1 induced maximum fluorescence enhancement. However, the metal-enhanced fluorescence was dependent on the emission wavelength of tryptophan, and this phenomenon was closely related to the metal surface reabsorption process (inner filter effect), suggesting that the plasmon resonance reabsorption effect should be taken into account in analyses involving protein studies by metal-enhanced fluorescence.  相似文献   
65.
Some heteroaromatic esters were reduced to the corresponding alcohols by using a sodium borohydride–methanol system. The reduction was completed within 0.15–2.0 h in refluxing THF. The alcohol products were isolated after aqueous workup in moderate to excellent yield (48–97%).  相似文献   
66.
Ultrasonic irradiation substantially improves the reaction of cyclohexene with I2 in aqueous dioxane in the presence of Cu(OAc)2 · H2O to generate the expected iodohydrin in high yield. The product undergoes cyclization to the epoxide by biphasic treatment with either Na2CO3 or KOH in a sonication‐sensitive step.  相似文献   
67.
Ni0.04Zn0.96O and Fe0.03Zn0.97O with average diameter of 23 and 19 nm, respectively, have been synthesized by a modified sol–gel method to be used in the preparation of (100 − x)/x poly(vinyl alcohol)/oxide nanocomposite films, with x = 0, 1, 3 and 5 (in wt.%). A 125 W-Hg vapor lamp with emission above 254 nmwas used to irradiate PVA/Ni0.04Zn0.96O and PVA/Fe0.03Zn0.97O films. The effect on their structural, thermal, morphological and optical properties was studied by TG, DSC, DRX, AFM, UV–vis and PL spectrophotometry. The Ni0.04Zn0.96O addition on PVA films decreases the thermal stability of the polymer in inert and in oxidative atmosphere. In contrast, the Fe0.03Zn0.97O presence in the PVA films seems to increase the thermal stability of the polymer. The characteristic peak of the crystalline phase of PVA and wurtzite phase of the zinc oxide were identified through X-ray diffraction in both films. The crystallinity of the PVA film increases with UV irradiation and with the presence of Ni0.04Zn0.96O and Fe0.03Zn0.97O. The roughness of the PVA film was not modified by the addition of the doped oxides; however, it increases after UV irradiation, more significantly in the films containing the oxides. The PVA film exhibits absorption around 280 nm characteristic of π–π transitions related to carbonyl groups from residuals acetate, while the 95/05 PVA/Ni0.04Zn0.96O and 95/05 PVA/Fe0.03Zn0.97O nanocomposite films show absorption at the visible region which is characteristics of the band gap reduction of the doped oxides. The photoluminescence of PVA was modified by the presence of the oxides in the film. These nanocomposite films are interesting due to their thermal, mechanical (flexible) properties and low cost of production. In addition they are also able to exhibit peculiar optical properties showing potential to be used in photonic devices, gas sensors and organic solar cell applications.  相似文献   
68.
69.
Glycodendrimers are neoglycoconjugates that can be considered as bioisosters of glycoproteins, since they can mimic the multivalent interactions of lectin-carbohydrate. The ability of glycodendrimers to present multivalent interactions with lectins as compared to a monovalent ligand is referred to as “cluster effect”. It is expected that, because of the cluster effect, glycodendrimers would result in a better association with lectins than mono-carbohydrate anchored systems. Radioisotopes are useful to evaluate biodistribution of molecules. This study is important to obtain information about molecule–receptor interactions. Indeed, such study can provide an exquisite tool to evaluate the affinity of certain molecules to specific areas in the body, leading to the development of new radiopharmaceuticals and/or drug delivery systems. Herein, we describe a d-galactose coated low molecular weight PAMAM G0 dendrimer that was successfully radiolabeled with technetium-99m. Biodistribution studies and scintigraphic images were performed in healthy mice. It was observed high liver uptake which was significantly reduced in blocking studies, indicating hepatic specificity. Therefore, low molecular weight glycodendrimer can be considered as useful platform for selective targeting of drugs to the liver and to assess hepatic function.  相似文献   
70.
The aim of this study was to investigate the effect of the support material used for biomass attachment and bed porosity on the potential generation of hydrogen gas in an anaerobic bioreactor treating low-strength wastewater. For this purpose, an upflow anaerobic packed-bed (UAPB) reactor fed with sucrose-based synthetic wastewater was used. Three reactors with various support materials (expanded clay, vegetal coal, and low-density polyethylene) were operated for hydraulic retention time (HRT) of 0.5 and 2 h. Based on the results obtained, three further reactors were operated with low-density polyethylene as a material support using various bed porosities (91, 75, and 50 %) for an HRT of 0.5 h. The UAPB reactor was found to be a feasible technology for hydrogen production, reaching a maximum substrate-based hydrogen yield of 7 mol H2 mol?1 sucrose for an HRT of 0.5 h. The type of support material used did not affect hydrogen production or the microbial population inside the reactor. Increasing the bed porosity to 91 % provided a continuous and cyclic production of hydrogen, whereas the lower bed porosities resulted in a reduced time of hydrogen production due to biomass accumulation, which resulted in a decreasing working volume.  相似文献   
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