不同制备方法、载体材料对穿心莲内酯固体分散体重结晶稳定性的影响

目的考察不同制备方法、载体材料对穿心莲内酯固体分散体重结晶稳定性的影响。方法选择PEG8000、PVP K30、P188、Soluplus^■作为载体材料,分别采用真空干燥法、喷雾干燥法、冷冻干燥法制备固体分散体。在温度(40±2)℃、相对湿度(75±5)%下,X射线衍射测定穿心莲内酯相对结晶度。结果以PEG8000、PVP K30、P188为载体材料时,真空干燥法所制备固体分散体的结晶峰强度最高;以Soluplus^■为载体材料时,冷冻干燥法所制备固体分散体的结晶峰强度最高。在3种制备方法下,PVP K30稳定性最高,P188稳定性最低。12种固体分散体相对结晶度有显著差异(P<0.05)。结论制备方法、载体材料均可影响穿心莲内酯固体分散体的重结晶稳定性,后者为主要影响因素。

基于多效应稳定剂改善药物纳米结晶稳定性研究进展

近年来,在药物研发过程中,难溶性药物面临其生物利用度低和吸收效果不佳的难题,药物纳米结晶以其纳米尺寸和独特的理化性质可有效增加药物溶解度和渗透性,且具有辅料用量少,载药量高和不良反应少等优势而备受关注,但不稳定性限制了其进一步发展,多效应稳定剂可以通过空间位阻、静电斥力及溶剂化等作用显著提高其稳定性。笔者通过查阅并整理相关文献,从药物纳米结晶的主要特性和局限性、多效应稳定剂的分类及其在体内外行为中应用进展3个方面进行综述,以期为药物纳米结晶及其制剂研发提供借鉴。

Effects of magnesium and cooling rate on titanium phase transformation for production of TiO_2

X-ray diffraction（XRD） and crystal structure analysis were used to study the effects of Mg content and cooling rate on the titanium phase transformation of three types of titanium slag. The results indicate that in the rapid cooling process, the titanium phase is anosovite, whose chemical formula is MgnTi（3-n）O5（0n1）. In the slow cooling process, when the Mg content is high, anosovite transforms into karrooite MgTi2O5 structure; when the Mg content is low, karrooite MgTi2O5 and rutile TiO2 both exist. The stability of karrooite MgTi2O5 is better than that of anosovite MgnTi（3-n）O5. Slow cooling contributes to the doping of Mg into the anosovite crystal and stabilises the anosovite crystal structure.

Assessment of the Stability of Cefazolin Sodium in Solids by TGA Decomposition Kinetics

\ According to the analysis of the residual products by thermogravimetric analysis (TGA), the thermal decomposition process of cefazolin sodium (CEZ·Na) was thought to be similar to the degradation in solid state in its storage time. This laid a foundation for estimating the relative chemical stability of the drug by determination of its decomposition kinetics using TGA. Although the observed thermal decomposition kinetics of CEZ·Na was complex, a conversion level of 1% was chosen for evaluation of the stability of CEZ·Na crystalline since the mechanism here was more likely to be that of the actual product failure. The evaluation results suggested that the α form of CEZ·Na had the best stability and the amorphous one was the least stable one among α form, dehydrated α form and amorphous form.

Effect of Na_(2)O on transition and stability of dicalcium silicate based on sintering process

The phase transition,morphology,stability and pulverization performance of dicalcium silicate(C_(2)S)with different Na_(2)O additions during the high-temperature sintering process were studied using XRD,SEM-EDS,FT-IR,and Raman spectra methods.When the CaO to SiO_(2) molar ratio is 2.0 and the Na_(2)O to SiO_(2) molar ratio is below 0.20,the crystalline calcium silicate compounds includeγ-C_(2)S andβ-C_(2)S.As the Na_(2)O addition increases,the proportion,crystallinity and grain size ofβ-C_(2)S in the sintered products increase,those parameters ofγ-C_(2)S decrease,and the content of amorphous phase increases.Na_(2)O mainly forms solid solutions inβ-C_(2)S and inhibits the transition ofβ-C_(2)S toγ-C_(2)S,resulting in the sintered products unpulverized.The stability of sintered products in alkali solution decreases significantly with the increasing Na_(2)O additions,and theβ-C_(2)S solid solution with Na_(2)O is less stable thanγ-C_(2)S.The mechanism that Na_(2)O affects the transition of C_(2)S as well as its stability was also discussed,which can give actual guidance for the treatment of low-grade alumina-containing resources by the sintering process.

Effect of strain rate on microstructural evolution and thermal stability of 1050 commercial pure aluminum

Effects of strain rate on the microstructure evolution and thermal stability of1050commercial pure aluminum processed by means of split Hopkinson pressure bar(SHPB)and Instron?3369mechanical testing machine were investigated.Samples in the deformed state and after various annealing treatments at423?523K(150?250°C)for1h were characterized by TEM and hardness test.The result reveals that the samples in the deformed state were mainly composed of elongated subgrains/cells with high density of dislocations.Microstructures of the quasi-static compressed aluminum were quite stable throughout the temperature range studied,and no significant grain growth was observed.However,for the dynamic impacted one,recrystallized grains with an average grain size of4.7μm were evolved after annealing at523K(250°C)for1h.It is suggested that the annealing behavior of this dynamic deformed aluminum is a continuous process of grain coarsening,rather than the traditional discontinuous recrystallization for the quasi-static compressed aluminum.

Insight into the degradation mechanism of cefixime under crystallization condition

The chemical stability of cefixime was determined by high-performance liquid chromatography （HPLC） under different conditions, including factors such as pH, solvents, initial concentration, temperature and additives. The degradation process follows the first-order kinetics. A pH-rate profile exhibits the U-shape and shows the maximum stability of cefixime at pH = 6. The stability in different pure solvents is ranked as acetone 〉 ethanol 〉 methanol 〉 water, while the degradation rate of cefixime exists a maximum at the ratio of 0.6 in water ＋ methanol mixtures. In addition, the degradation rate increases with the temperature increasing and the activation energy of degradation was found to be 27.078 kJ. mol- 1 in acetone ＋ water mixed solvents. The addition of different additives was proven to either inhibit or accelerate the degradation. The degradation products were analyzed using HPLC, LC-MS and infrared spectroscopy, and the possible degradation pathways in acid as well as alkaline environment were proposed to help us understand the degradation behavior of cefixime.

Stability of thin films of microcrystalline silicon under ligh tsoaking

Silicon thin films with different crystalline ratio(Xc) have been deposited by varying silane content(SC) of reactive gases in the RF-PECVD process.The effects of silane content on performance of the materials and the relationship between microstructure and opto-electronic properties were studied by means of Raman measurements,photoconductivity(σ_ ph ),and dark conductivity(σ_d),followed by the measurements of light absorption coefficient(α),the product of quantum efficiency,mobility and lifetime (ημτ),before,during and after light soaking,respectively.The results indicate that the microcrystalline silicon near the transition region is suitable to prepare microcrystalline silicon of device grade,and that the amorphous region of the material is responsible to the light induced degradation.

Crystal structure of histidine-containing phosphocarrier protein from Thermoanaerobacter tengcongensis MB4 and the implications for thermostability

Protein thermostability is an inherent characteristic of proteins from thermophilic microorganisms,and therefore enables these organisms to survive at extreme temperatures.Although it is well-known that thermostable proteins are critical for the growth of thermophilic organisms,the structural basis of protein thermostability is not yet fully understood.The histidine-containing phosphocarrier (HPr) protein,a phosphate shuttle protein in the phosphoenolpyruvate-dependent sugar transport system (PTS) of bacterial species,is an ideal model for investigating protein thermostability with respect to its small size and deficiency in disulphide bonds or cofactors.In this study,the HPr protein from Thermoanaerobacter tengcongensis (TtHPr) is cloned and purified.Crystal structure with good quality has been determined at 2.3 resolution,which provides a firm foundation for exploring the thermostable mechanism.However,it shows that the crystal structure is conserved and no clue can be obtained from this single structure.Furthermore,detailed comparison of sequence and structure with the homologs from mesoor thermophilic bacteria shows no obvious rule for thermostability,but the extra salt-bridge existing only in thermophilic bacteria might be a better explanation for thermostability of HPr.Thus,mutations are performed to interrupt the salt-bridge in HPrs in thermophilic bacteria.Using site-directed mutations and the circular dichroism method,thermostability is evaluated,and the mutational variations are shown to have a faster denaturing rate than for wild-type viruses,indicating that mutations cause instability in the HPrs.Understanding the higher-temperature resistance of thermophilic and hyperthermophilic proteins is essential to studies on protein folding and stability,and is critical in engineering efficient enzymes that can work at a high temperature.