共查询到20条相似文献,搜索用时 31 毫秒
1.
Yong Youn Hwang Dong Chul Shin Yoon Sung Nam Byung-Kwan Cho 《Journal of Industrial and Engineering Chemistry》2012,18(4):1412-1417
β-Cyclodextrin (β-CD) is widely used to increase the stability, solubility, and bioavailability of poorly soluble drugs because of the appropriate size of its cavity. Sibutramine is a neurotransmitter reuptake inhibitor that has been investigated as an oral anorexiant. Here we report the complexation of sibutramine base with β-CD and the stability, dissolution, and pharmacokinetic properties of the sibutramine/CD complex. The formation of sibutramine/β-CD inclusion complexes is confirmed using differential scanning calorimetry, X-ray diffractometry, and 1H nuclear magnetic resonance. The thermal and photochemical stability of sibutramine is significantly improved by the complexation with β-CD, and the pharmacokinetic parameters (e.g., the plasma concentration, area under the curve, and maximum concentration of two active metabolites) for humans are comparable with those of the commercialized standard product (Reductil®). Our study suggests that sibutramine/β-CD complexation can be of great use to increase the stability and biological efficacy of sibutramine base. 相似文献
2.
3.
《Ceramics International》2020,46(9):13695-13703
Manganese–copper ferrite (MCFO) and dysprosium (Dy)-doped manganese–copper ferrite nanocomposites (Mn0.5Cu0.5DyxFe2−xO4) (x = 0, 0.05, 0.10, and 0.15) were synthesized by sonochemical method. Crystal structure and the structural parameters of the MCFO were analyzed based on the doping concentration of Dy ion. It was observed that the average crystalline size of the synthesized nanocomposite decreases when the concentration of Dy increases. The existing spherical surface morphology of the MCFO and Dy-doped MCFO nanocomposites were obtained through scanning electron microscopy. In the UV spectrum, the pristine MCFO sample showed an absorbance peak at 743 nm whereas the absorbance values of Dy-doped ferrite nanocomposite considerably shifted (blue) toward a lower wavelength (231–222 nm). The dielectric parameters of all ferrite nanocomposites were studied in the frequency range of 100 Hz to 5 MHz. The dielectric spectrum revealed that dielectric constant and loss tangent decreased with increased doping concentration of Dy ion. The saturation magnetization also changed with Dy doping in MCFO. The impact of Dy on manganese–copper ferrite changed the optical, dielectric and magnetic properties of the prepared binary ferrite nanocomposite, which can be used for microwave-absorbing material applications. 相似文献
4.
Styrene-butadiene-styrene (SBS) modified asphalt (SMA) has been widely used in road engineering for decade. However, the phase separation of SMA was obvious during the transport and SBS degraded after aging. To resolve these problems, β-cyclodextrin (β-CD) was used to modify SMA in this work. Conventional properties, storage stability, the effect of short-term aging on the morphology, and rheological property for SMA and β-CD/SMA were investigated. The softening point of modified asphalt reached to the maximum of 66.7°C when 1 wt% β-CD was added to SMA, where the penetration had shown the minimum of 80.8 dmm. In addition, the ductility of β-CD/SMA increased to the maximum of 797 mm when the content of β-CD was increased to 5 wt%. Furthermore, incorporation of β-CD improved the storage stability of SMA. Importantly, the aggregation of SBS was observed in β-CD/SMA, but modifiers distributed uniformly after a short-term aging. The rutting resistance and antiaging performances of SMA were also improved by the addition of β-CD. Considering the comprehensive properties of modified asphalt, the optimum content of β-CD was found to be 2 wt%. 相似文献
5.
The poor flexibility, low toughness and thermal stability have restricted the applications of degradable poly(lactic acid) bioplastic. The introduction of deoxyribonucleic acid, whey protein or collagen with helical structures, which include numerous intermolecular hydrogen bonds, can produce changes in mechanical and thermal properties of poly(lactic acid) materials. Due to the presence of more –C?=?O and –NH groups with strong hydratability, different composites exhibited a higher heat resistance compared with the neat poly(l-lactic acid). Moreover, for collagen/poly(l-lactic acid) composites, the tensile strength and elongation at break were increased by 88.6 and 154.9% compared with the neat poly(l-lactic acid), respectively. The results provide a basis for the design of novel poly(lactic acid)-based composites and can expand the application areas of materials, including plastic films, taker-bags, textiles and so on. 相似文献
6.
Amit Prakash Siddheswar Maikap Writam Banerjee Debanjan Jana Chao-Sung Lai 《Nanoscale research letters》2013,8(1):379
Improved switching characteristics were obtained from high-κ oxides AlOx, GdOx, HfOx, and TaOx in IrOx/high-κx/W structures because of a layer that formed at the IrOx/high-κx interface under external positive bias. The surface roughness and morphology of the bottom electrode in these devices were observed by atomic force microscopy. Device size was investigated using high-resolution transmission electron microscopy. More than 100 repeatable consecutive switching cycles were observed for positive-formatted memory devices compared with that of the negative-formatted devices (only five unstable cycles) because it contained an electrically formed interfacial layer that controlled ‘SET/RESET’ current overshoot. This phenomenon was independent of the switching material in the device. The electrically formed oxygen-rich interfacial layer at the IrOx/high-κx interface improved switching in both via-hole and cross-point structures. The switching mechanism was attributed to filamentary conduction and oxygen ion migration. Using the positive-formatted design approach, cross-point memory in an IrOx/AlOx/W structure was fabricated. This cross-point memory exhibited forming-free, uniform switching for >1,000 consecutive dc cycles with a small voltage/current operation of ±2 V/200 μA and high yield of >95% switchable with a large resistance ratio of >100. These properties make this cross-point memory particularly promising for high-density applications. Furthermore, this memory device also showed multilevel capability with a switching current as low as 10 μA and a RESET current of 137 μA, good pulse read endurance of each level (>105 cycles), and data retention of >104 s at a low current compliance of 50 μA at 85°C. Our improvement of the switching characteristics of this resistive memory device will aid in the design of memory stacks for practical applications. 相似文献
7.
Ping Shen Xinping LiuShenghui Jiang Ling WangLing Yi Dandan YeBin Zhao Songting Tan 《Dyes and Pigments》2012,92(3):1042-1051
Four novel D-π-A hydrazone dyes (HT, HM, HE, and HO) with an N, N-diphenylhydrazone moiety as the electron donor, different thiophene-derived π-conjugated bridges and a cyanoacrylic acid moiety as the electron acceptor have been designed and synthesized for the application in dye-sensitized solar cells. The influences of thiophene-derived bridges on the photoelectrochemical and photovoltaic performance of these hydrazone dyes were investigated. Results demonstrate that the introduction of 3,4-dialkyloxythiophene could red-shift the dye’s absorption spectrum due to the enhancement of the electron-donating ability of π-conjugated bridges. Importantly, electrochemical impedance spectroscopy analysis reveal that 3,4-dialkyloxythiophene bridge could change the charge recombination resistance at the TiO2/dye/electrolyte interface and as a result to improve the open-circuit photovoltage. Among the four dyes, HO exhibits the maximum power conversion efficiency of 5.83% (Voc = 0.65 V, Jsc = 12.69 mA/cm2, FF = 0.707) under simulated AM 1.5 irradiation (100 mW/cm2). 相似文献
8.
Saul Sanchez-Valdes 《Journal of Adhesion Science and Technology》2016,30(9):1006-1016
This work analyses the effect of using ethylene-propylene-diene-monomer-grafted maleic anhydride (EPDM-g-MA) as compatibilizer to improve the interfacial properties and toughness of high-density polyethylene–organoclay–silver (HDPE/clay/silver) nanocomposites. EPDM-g-MA was reacted using ultrasound with a solution of AgNO3 0.04 M and ethylene glycol using ammonium hydroxide to obtain the silver ammonium complex. This silver-coated maleated EPDM was then melt mixed with HDPE and organoclay (Nanomer I28E) using a twin-screw extruder. Transmission electron microscopy (STEM) and X-ray diffraction (XRD) results confirmed the filler dispersion of both organoclay and silver nanoparticles into HDPE matrix when maleated EPDM was used. Both fillers were better dispersed and exfoliated by using this compatibilizer. The thermal stability enhancement of nanocomposites was confirmed using thermogravimetric analysis. Mechanical and antimicrobial properties demonstrated that better dispersed filler obtained with maleated EPDM enhanced the toughness and antimicrobial behaviour of HDPE/clay/silver hybrid nanocomposites. This confirmed that maleated EPDM was an efficient compatibilizer to obtain hybrid nanocomposites with enhanced properties to be used for several HDPE applications. 相似文献
9.
A study on the catalytic performance of Pd/γ-Al2O3, prepared by microwave calcination, in the direct synthesis of dimethylether 总被引:1,自引:0,他引:1
Ruizhi Chu Xianyong Wei Zhimin Zong Wenjia Zhao 《Frontiers of Chemical Engineering in China》2010,4(4):452-456
A series of Pd/γ-Al2O3 hybrid catalysts were prepared by impregnation and subsequent calcination under microwave irradiation. The catalysts were
used for direct synthesis of dimethylether (DME) from syngas. The results show that calcination under microwave irradiation
improved both the activity and selectivity of the catalysts for DME synthesis. The optimum power of the microwave was determined
to be 420 W. Under such optimum conditions, CO conversion, DME selectivity and time space yield of DME were 60.1%, 67.0%,
and 21.5 mmol·mL−1·h−1, respectively. Based on various characterizations such as nitrogen physisorption, X-ray diffraction, CO-temperature- programmed
desorption, and Fourier transform infrared spectral analysis, the promotional effect of the microwave irradiation on the catalytic
property was mainly attributed to both the higher dispersion of Pd and the significant increase in the adsorption on the CO-bridge
of Pd. Microwave irradiation with very high power led to the increase in CO-bridge adsorption and thereby decreased the catalytic
activity, whereas the coverage by metallic Pd of the active sites on acidic γ-Al2O3 significantly occurred under microwave irradiation with very low power, resulting in a decrease in the selectivity to DME. 相似文献
10.
Reza Shariatmadari Mohammadreza Kalaee Ramin Khajavi Zahra Shariatinia 《乙烯基与添加剂工艺杂志》2021,27(3):497-507
In order to enhance the heat stability of polyvinyl chloride (PVC), several heat stabilizing parameters such as metal content, antioxidant percentage, primary-to-secondary antioxidant ratios, stearic-to-acetylacetonate ratio, the amounts of pentaerythritol and β-diketone were studied using oven and Congo red tests. Results indicated that the percentage contribution of the calcium-to-zinc molar ratio in the static heat stability was 60.78%. Due to the synergistic effects of the calcium/zinc stabilizer and the zeolitic metal–organic framework (MOF) as an effective co-stabilizer, the heat stability was increased from 109 to 148 min. The EDX analysis was carried out to determine the mechanism of HCl gas absorption by the zeolitic imidazolate framework-8 (ZIF-8) existing in the PVC compound. Furthermore, the Ca/Zn thermal stabilizer showed poor electrical insulating properties, but the ZIF-8 improved electrical resistivity of the PVC compounds. Volume resistivity of ZIF-8 was significantly higher than that of the commonly used Ca/Zn stabilizers. Dynamic mechanical thermal analysis and tensile test of the PVC compound containing the ZIF-8 showed increased Tg and enhanced toughness. 相似文献
11.
《应用陶瓷进展》2013,112(7):391-395
Cf/ZrC, Cf/SiC and Cf/ZrC–SiC composites were successfully prepared by polymer infiltration and pyrolysis (PIP) using polycarbosilane and a liquid ZrC precursor. The densification process, mechanical properties and microstructures were studied in a view of comparison. After the same total 20 PIP cycles, the Cf/ZrC, Cf/SiC and Cf/ZrC–SiC composites had flexural strengths of 50.1±5.3, 285.7±22.6, 141.5±13.1?MPa respectively; elastic moduli of 7.8±0.9, 57.1±3.2 and 45.1±2.6?GPa respectively; and fracture toughness of 2.5±0.2, 10.4±0.9 and 10.9±1.1?MPa m1/2 respectively. With the introduction of high modulus SiC phase into the ZrC matrix, the densification and modulus of the matrix were improved; as a result, the Cf/ZrC–SiC composite showed higher mechanical properties compared to Cf/ZrC. 相似文献
12.
Saliha Alehyen Fatima Bensajjay Mohammed El Achouri Lourdes Pérez Aurora Pinazo María Rosa Infante 《Journal of surfactants and detergents》2010,13(3):339-348
A new oligomeric surfactant: N,N,N′,N″,N″- pentamethyl diethyleneamine—N,N″-di-[tetradecylammonium bromide] referred to as 14-2-N(CH3)-2-14 was synthesized, purified and characterized by Elemental Analysis, 1H and 13C NMR and Electrospray. The micellar properties of this compound were determined by electrical conductivity and surface tension
methods. Optical microscopy was also employed to study the behavior of anhydrous surfactant and the binary water/surfactant
system as a function of temperature. The critical micellar concentration (cmc), degree of counterion binding and thermodynamic
parameters of micellization (standard molar Gibbs energy, enthalpy and entropy of micellization) were determined by electrical
conductivity measurements in the temperature range [24–54 °C]. Surface tension measurements also provide information about
the dependence of the surface tension at the cmc (γcmc), pC20 (negative logarithm of the surfactant’s molar concentration C20, required to reduce the surface tension by 20 mN/m, the surface excess (Γmax) at air/solution interface, the minimum area per surfactant molecule at the air/solution interface (Amin), surface pressure
at the cmc (Пcmc), critical packing parameter(CPP) and the standard free energies of micellization (
\Updelta Gm0\Updelta G_{m}^{0}) and of adsorption (
\Updelta G\textads0 \Updelta G_{\text{ads}}^{0} ). 相似文献
13.
V. V. Popov Ya. V. Zubavichus V. F. Petrunin A. P. Menushenkov O. V. Kashurnikova S. A. Korovin R. V. Chernikov A. A. Yaroslavtsev 《Glass Physics and Chemistry》2011,37(5):512-520
It has been established that the process of producing the Ln2 + x
Me2 − x
O7 − x/2 (Ln = Gd, Dy; Me = Zr, Hf) nanocrystals by calcination of hydroxides, which, in turn, have been produced by coprecipitation
of metal salts, includes several stages. At the beginning, the X-ray amorphous structure of the precursors remains unchanged
during dehydration; during subsequent heating to 600–700°C, nanocrystals with a disordered fluorite structure begin to be
formed. An increase in the temperature above 700°C leads to an increase in the size of crystallites (coherent scattering regions).
This process is accompanied by changes occurring in their local structure. In the nanocrystalline powders of Cd2Hf2O7 and Gd2Zr2O7 synthesized at 1200°C (6 h), the pyrochlore-type superstructure with the lattice parameters doubled relative to fluorite
has been revealed. It has also been found that, possibly, the Dy2HfO5 sample at 1600°C (3 h) has a modulated structure. 相似文献
14.
Ayesha Kausar Irum Rafique Bakhtiar Muhammad 《Polymer-Plastics Technology and Engineering》2017,56(4):347-363
In this review, properties and potential of carbon nanotube, nanodiamond, and nanodiamond–carbon nanotube hybrid nanobifiller have been discussed with reference to electromagnetic interference shielding materials. The nanodiamond and carbon nanotube nanofiller and nanodiamond–carbon nanotube nanobifiller have outstanding electrical, thermal, and mechanical features. Main focus of review was electromagnetic interference shielding phenomenon and its implication in polymer/nanodiamond, polymer/carbon nanotube, and polymer/nanodiamond–carbon nanotube nanobifiller composite. The epoxy/nanodiamond, epoxy/carbon nanotube, and epoxy/nanodiamond–carbon nanotube composites have been discussed with electromagnetic interference shielding shielding features. Thus, considerable enhancement in electromagnetic interference shielding shielding features was observed using higher nanodiamond, carbon nanotube, and nanodiamond–carbon nanotube loadings. Significance and future potential of these polymeric composite are specified. 相似文献
15.
16.
The Content and Composition of Total,Free, and Esterified Sterols of Lotus Plumule Oil by GC–MS/FID
下载免费PDF全文
![点击此处可从《Journal of the American Oil Chemists](/ch/ext_images/free.gif)
Shuai Chen Yanlan Bi Shangde Sun Jingnan Chen 《Journal of the American Oil Chemists' Society》2017,94(3):363-373
This study investigated the content and composition of total, free, and esterified sterols of three varieties of lotus plumule oil (Hunan lotus, Jiangxi lotus, and Fujian lotus) using GC–MS/FID. The fatty acid composition of sterol fatty acid esters (SFAE) was also analyzed and compared with that of triglycerides. Results showed that total sterol of lotus plumule oil (12.10–14.21 g/100 g) was higher than that of other plant oils (corn germ oil, 1.11 g/100 g; rapeseed oil, 0.78 g/100 g). No significant difference was found among the total sterol contents of the three types of lotus plumule oils (p > 0.05). Most sterol existed in ester forms (81.8–89.1%) rather than in free forms (8.4–10.1%). β‐Sitosterol (71.4–73.4%), and campesterol (6.2–7.5%) were the predominant fractions of free sterols. β‐Sitosterol (41.3–53.7%) and ?5‐avenasterol (27.1–31.1%) were the predominant fractions of esterified sterols, followed by campesterol (12.1–13.0%) and ?7‐avenasterol (3.4–3.7%). Linoleic acid (63.6–65.8%), oleic acid (8.3–10.4%), and behenic acid (9.0–9.9%) were the main fatty acids of SFAE, which were different from those of triglycerides. The results from this study suggest that lotus plumule oil may be a good resource of SFAE and can be used as a supplemental ingredient in functional foods. 相似文献
17.
A. Rasche 《Electrochimica acta》2008,53(11):3812-3819
The anodic oxidation of N,N-dimethyl-p-toluidine (2) was studied using cyclic voltammetry and spectroelectrochemistry. In contrast to former studies, the experimental measurements showed that the radical cations of 2 reversibly dimerize at the methyl substituted p-position of the dimethylamino group and form σ-dimers. Theses results again clearly demonstrate that σ-dimerization takes place even when reactive sites are blocked by substituents such as alkyl or phenyl groups. The findings are also relevant for the interpretation of σ-dimerization during electropolymerization and charging of conducting polymers. 相似文献
18.
Reduced graphene oxide–zinc oxide/cyanate ester/bismaleimide resin (RGO–ZnO/CE/BMI) composites were synthesized via a blending method. The RGO–ZnO composite was incorporated into the CE/BMI copolymer to improve the properties of RGO–ZnO/CE/BMI composites. The structure, elements, and morphology of the RGO–ZnO composite were studied with XPS, FTIR, XRD, and SEM analyses. It indicated that the ZnO micro-sphere was attached to RGO by electrostatic attraction and the RGO–ZnO composite was prepared successfully. The mechanical properties and thermal stability of RGO–ZnO/CE/BMI composites were investigated. When RGO–ZnO composite was 1 wt.%, the flexural and impact strengths of RGO–ZnO/CE/BMI composites were 1.07 and 1.35 times of the CE/BMI copolymer, respectively. However, the RGO–ZnO composite tended to aggregate in the CE/BMI matrix with high loading. According to the SEM analysis, appropriate RGO–ZnO composite was evenly dispersed in the CE/BMI copolymer. Compared to the CE/BMI copolymer, the thermal stability of the RGO–ZnO/CE/BMI composites was good. Thus, the RGO–ZnO composite was successfully filled in the CE/BMI matrix; the mechanical properties and thermal stability of the RGO–ZnO/CE/BMI composites were enhanced. 相似文献
19.
The preparation of the TiO2, ZnO, and TiO2/ZnO nanofilms was conducted on glass via sol–gel process. The prepared film was detailedly characterized by means of OM, SEM, XRD, and EDS. The results showed that the obtained pure TiO2 was composed of nanoparticles. For pure ZnO it consisted of nanoparticles and large agglomerates. Both the microstructural morphology and the crystallization of the prepared TiO2/ZnO composite film were strongly related to the Ti/Zn ratio in the film. With a Ti/Zn ratio less than 1/1, the composite film was absence of cracks. Poor crystallization was definitely observed for the composite film with Ti/Zn ratio of 3/1 and 1/1. The EDS analysis revealed homogeneous distribution of Ti and Zn elements in the film. 相似文献
20.
Dongxia Liu Yaritza M. López-De Jesús John R. Monnier Christopher T. Williams 《Journal of Catalysis》2010,269(2):376-387
A series of silica-supported Pt, Ru, and Pt–Ru catalysts has been synthesized using dendrimer–metal nanocomposite (DMN) precursors prepared by both co- and sequential complexation with metal salts. The catalysts have been characterized by several techniques, including electron microscopy, temperature-programmed titration of adsorbed oxygen, and X-ray diffraction. Liquid-phase selective hydrogenation of 3,4-epoxy-1-butene (EpB) was used as a probe reaction to evaluate their catalytic performance. The bimetallic catalyst prepared by the co-complexation method exhibits a superior catalytic activity compared to the sequential one, and is much more active than a conventional catalyst prepared by incipient wetness. The activity enhancement is attributed to a bifunctional performance of the PtRu alloy sites created, based on a strong correlation between turnover frequencies, and both the alloy compositions and metal surface site distributions. In addition, the co-complexation catalyst is selective toward crotonaldehyde, suggesting that this reaction pathway is favored on the PtRu sites. 相似文献