排序方式: 共有13条查询结果,搜索用时 265 毫秒
1.
Edina Vranić Daris Grizić Odon Planinšek Stanko Srčič Erem Bilensoy 《Journal of inclusion phenomena and macrocyclic chemistry》2014,80(1-2):139-146
Cyclodextrins are cyclic oligosaccharides, capable of forming inclusion complexes with many active substances. This way, the aqueous solubility and rate of dissolution of active substances can be changed. For this research we have selected celecoxib as the model active substance, due to its low water solubility, high lipophilicity, and high intestinal permeability. Usually, the amount of cyclodextrin complex that can be incorporated into a pharmaceutical dosage form is limited. The usage of hydrophilic polymers can overcome this problem. In this study, we wanted to point out the potential of various types of hydrophilic polymers for enhancing the complex formation efficiencies, and to highlight the possible use of alginate as a solubility stabilizer/enhancer and as a microsphere matrix polymer. The phase solubility investigation showed greater stability constants (> 250 M?1) in ternary complexes than in the binary complex, which is a good indicator of the complex formation enhancer properties of these hydrophilic polymers. The relative solubilizing efficiency decreased in the next order: PVP K25 (6.49) > Sodium alginate (6.26) > PEG 6000 (5.72) > without polymer (4.81). The DSC curves showed that all samples that were prepared with β-cyclodextrin (both complexes and physical mixtures) had lower melting endotherms at 160 °C than pure celecoxib. XRD confirmed the complex formation by partial celecoxib amorphisation. The dissolution studies of the prepared microspheres revealed that all samples had different release rates (shown by the similarity factor f2, which was 36.37, 42.46 and 38.11 % respectively) and that the use of β-cyclodextrin increased the dissolution rate of celecoxib from alginate microspheres in a controlled manner. We concluded that sodium alginate could act as a complex stabilizing/enhancing agent and as a microsphere matrix polymer, at the same time. 相似文献
2.
3.
Matthew A. Papanikolas Mathew D. Rogers Detchat Samart 《Mathematische Zeitschrift》2014,276(3-4):1151-1163
The aim of this paper is to prove a Mahler measure formula of a four-variable Laurent polynomial whose zero locus defines a Calabi–Yau threefold. We show that its Mahler measure is a rational linear combination of a special \(L\)-value of the normalized newform in \(S_4(\Gamma _0(8))\) and a Riemann zeta value. This is equivalent to a new formula for a \(_6F_5\)-hypergeometric series evaluated at 1. 相似文献
4.
本文制备了用于费托合成反应的钴改性Fe3O4-MnO2双功能催化剂,并探究了钴负载量对Fe-Co协同效应的影响以及Fe1CoxMn1催化剂的费托合成反应性能. 实验发现,在Fe3O4-Mn催化剂中加入Co可促进铁氧化物的还原、增加反应过程中铁位点的活性. 此外,Co的加入可增强Fe-Co金属间的电子转移,加强两者的协同作用,提高催化性能. Co负载较高的Fe1CoxMn1催化剂可进一步促进加氢反应能力,使产品分布向短链烃方向转移. 在280 °C、2.0 MPa和3000 h-1的最佳工况条件下,Fe1Co1Mn1催化剂的液体燃料收率最高. 相似文献
5.
6.
7.
8.
Detchat Samart 《The Ramanujan Journal》2013,32(2):245-268
In this paper we prove that the Mahler measures of the Laurent polynomials (x+x ?1)(y+y ?1)(z+z ?1)+k 1/2, (x+x ?1)2(y+y ?1)2(1+z)3 z ?2?k, and x 4+y 4+z 4+1+k 1/4 xyz, for various values of k, are of the form r 1 L′(f,0)+r 2 L′(χ,?1), where $r_{1},r_{2}\in \mathbb{Q}$ , f is a CM newform of weight 3, and χ is a quadratic character. Since it has been proved that these Mahler measures can also be expressed in terms of logarithms and 5 F 4-hypergeometric series, we obtain several new hypergeometric evaluations and transformations from these results. 相似文献
9.
Banjong Boonchom Samart Kongtaweelert 《Journal of Thermal Analysis and Calorimetry》2010,99(2):531-538
The kinetics and thermodynamics of the thermal dehydration of aluminum phosphate monohydrate, AlPO4 · H2O were studied using thermogravimetry (TG-DTG-DTA) at four heating rates in dry air atmosphere. The activation energies of
the dehydration step of AlPO4 · H2O were calculated through the methods of Friedman (FR) and Flynn–Wall–Ozawa (FWO) and the possible conversion function has
been estimated through the Achar and Li–Tang equations. The independent activation energies on extent of conversions and the
better kinetic model of the dehydration reaction for AlPO4 · H2O indicate single kinetic mechanism and the F
2.05
model as a simple n-order reaction of “chemical process or mechanism no-invoking equation”, respectively. The positive values
of ΔH# and ΔG# for the dehydration reaction show that it is endothermic and non-spontaneous process and it is connected with the introduction
of heat. The kinetic and thermodynamic functions calculated for the dehydration reaction by different techniques and methods
were found to be consistent. 相似文献
10.
Chanatip Samart Surachai Karnjanakom Chaiyan Chaiya Prasert Reubroycharoen Ruengwit Sawangkeaw Metta Charoenpanich 《Arabian Journal of Chemistry》2019,12(8):2028-2036
The experimental parameters for biodiesel production from para rubber seed oil and methanol using a SO3H-MCM-41 catalyst were optimized statistically. The SO3H-MCM-41 catalyst was synthesized by co-condensation in the presence of tetraethyl orthosilicate, 3-mercaptopropyl (methyl) dimethoxysilane (MPMDS) and cetyl-trimethylammonium bromide. In the last step, the solid catalyst (SH-MCM41) was oxidized by H2O2 to SO3H-MCM-41. The acid capacity of the obtained SO3H-MCM-41 catalyst was quantified by back titration with 0.1 M sodium hydroxide. The physical and chemical properties of the SO3H-MCM-41 were characterized by nitrogen adsorption/desorption, X-ray diffractometry, Fourier transform infrared spectroscopy and thermogravimetric analysis. The effect of varying the catalyst loading (wt.%), reaction time (h) and temperature (°C) and molar composition of MPMDS on the biodiesel yield were investigated using a 2k factorial design. The optimal conditions to maximize the biodiesel yield, obtained from the response surface analysis using a Box–Behnken design, was a 14.5 wt.% catalyst loading, and a reaction time and temperature of 48 h and 129.6 °C. Under these conditions a fatty acid methyl ester (biodiesel) yield of 84% was predicted, and an 83.10 ± 0.39% yield experimentally obtained. 相似文献