Kinetics of release of particulate solutes incorporated in cellulosic polymer matrices as a function of solute solubility and polymer swellability. I. Sparingly soluble solutes

A comparative study has been made of the kinetics of release into water of simple hydrophilic, but sparingly soluble, solutes (exemplified by CaSO₄ or SrSO₄) incorporated in varying amounts in cellulosic polymer matrices of low or high water swellability. Hydrophobic cellulose acetate films (cast from an acetone dope containing a dispersion of the appropriate salt particles occupying a fractional volume ϵ_N = 0.1–0.4 in the loaded hydrated matrix) were found to be particularly useful for this purpose because they could be easily hydrolyzed to cellulose, thus producing hydrophilic polymer matrices containing identical amounts and distributions of solute particles. The kinetic behavior observed exhibited the same main features as previously noted in drug release studies. Thus, a √t kinetic law was obeyed in all cases (apart from a relatively short initial period), while the diffusion coefficient calculated by application of the Higuchi model tended to rise with increasing solute load. This tendency was very strong in the case of the hydrophobic weakly swollen matrix and much weaker in the case of the hydrophilic one. On the reasonable assumption that the diffusion of solute in the salt-depleted matrix (which controls the release rate) occurs via aqueous pathways, the tortuosity τ of these pathways was calculated and found to attain extremely high values in the case of lightly loaded (ϵ_N = 0.1) matrices. These high τ values were drastically reduced upon either (1) increase of the salt load or (2) hydrolysis to cellulose. This behavior is shown to result from the fact that at ϵ_N = 0.1, the salt particles were fully coated with cellulose acetate so that water taken up to fill the space vacated by released salt is in the form of globules dispersed in a weakly hydrated polymer matrix and, hence, is ineffective in providing continuous aqueous pathways. In (1), these globules are increasingly bridged by gaps left in the original loaded matrix, as a result of incomplete coating of the solute particles with polymer. In (2), bridging is similarly effected by the formation of aqueous pathways through the polymer when its degree of hydration is sufficiently increased. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 277–287, 1998     

服装企业网络信息发布研究

文章分析了我国服装企业利用网络进行信息发布所存在的不足,提出了中国服装企业在网络信息发布方面应注意的问题。     

Preparation,Characterization and Biodegradation Characteristics of Poly(adipic anhydride-co-D,L -lactide)

Poly(adipic anhydride-co-D ,L -lactide) (P(AA-LA)) has been synthesized by ring-opening polymerization of adipic anhydride (AA) and D ,L -lactide (LA) using stannous octoate as catalyst in bulk and in solution. The copolymers were characterized by IR, nuclear magnetic resonance, gel permeation chromatography and differential scanning calorimetry. The physical properties can be tailored by varying the copolymer compositions, and showed low glass transition temperature, melting temperature and good solubility in common solvents. In vitro tests showed that after rapid weight loss in the first day, a constant degradation rate was observed. The release profiles of model drugs, bovine serum albumin and norethindrone over 16 days followed closely that of the degradation of copolymers containing higher amounts of AA (AA>64mol%), suggesting that the release mechanism was controlled predominantly by surface erosion. However, a large deviation from the close correlation of polymer degradation and drug release was observed for copolymers containing lower amounts of AA (<30mol%). These materials may be useful in protein delivery systems. © 1997 SCI.     

pH-responsive release from polypeptide microcapsules

Microcapsules were prepared from [Glu(OMe)]_m(Sar)_n (m = 21, n = 19) and [Lys(Z)]_m(Sar)_n (m = 27, n = 15), and were chemically modified to obtain a pH-responsive releasing membranes. One membrane was prepared by partially deprotecting the ester groups of [Glu(OMe)]_m(Sar)_n. The other membrane was prepared by connecting of poly(Glu) to side chain amino groups that were generated by a partial deprotection of [Lys(Z)]_m (Sar)_n. Consequently, two types of polypeptidic microcapsules were prepared; Glu residues in the main chain, and Glu residues in the graft chains on the positively charged main chain. Both microcapsules showed pH-responsive release of FITC-dextran encapsulated in the microcapsules. The release rate became slower in the medium at pH 3.0 than pH 7.5. Optical microscope observation revealed that partially deblocked [Glu(OMe)]_m(Sar)_n microcapsules swelled more at pH 7.5 than at pH 3.0; hence, enhanced permeation through the polypeptide membrane at pH 7.5. However, the shape of poly(Glu)-grafted [Lys(Z)]_m(Sar)_n microcapsules changed a little by changing pH of the medium. It is suggested that ion-pairing between carboxylate groups of poly(Glu) and ammonium groups of Lys acts as crosslinking to give the shape stability. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 453–458, 1997     

电加热管二维温度场计算

针对水平管、倾斜管中单相流及两相流由于自然对流的影响而使壁温、传热系数沿周向表现出不均匀性．提出了利用外壁面的两个边界条件来克服内壁西边界条件的不足．采用“径向节点内缩”技术的电加热管二维温度场数值计算模型。同时用并联网格电阻发热的概念处理非均匀内热源项。用此模型处理了Φ３２×３ｍｍ微倾斜管高压汽水两相流传热数据,结果令人满意。     

涂布包裹新型肥料技术

对缓释肥料的概念、分类、制作方法、作用机理、释放机理、应用和评价等方面进行综述。分析我国控释和缓释肥料研制的现状和进展,重点介绍上海化工研究院开发的涂布包裹技术,及该技术用于硫基复肥增氮或尿基复肥包硫的实施情况,还介绍了开发的转鼓涂布包裹机、尿素快速熔融器等专用设备情况,指出涂布包裹技术进一步工业实施应注意的问题和方向。     

钻屑残渣制备沥青路面面层重金属释放特征研究

目的 为进一步拓宽油基岩屑脱油残渣资源化利用途径,采用脱油残渣、矿粉、碎石等为原料,进行脱油残渣制备沥青路面可行性研究。方法 采用JTG/T F40-2004《公路沥青路面施工技术规范》、GB/T 30810-2014《水泥胶砂中可浸出重金属的测定方法》和EA NEN 7375-2004《模制或整体式块状材料的浸出特性标准》方法,考查了剩余固相替代矿粉制备的沥青面层试块的产品质量,分析了沥青面层重金属有效释放量和释放特性。结果 当剩余固相掺加量不高于4.8%(质量分数)时,制备出的沥青路面面层试块各项性能指标均符合JTG/T F40-2004要求。沥青面层试块浸出液中11种重金属(砷、钡、钴、铜、铬、锰、钼、镍、铅、钒、锌)释放率均低于1%。沥青面层试块中各重金属释放机理具有差异,其中砷、铬的释放机理主要为溶解作用,钡、钴、锰、镍、铅的释放机理主要为表面冲刷,剩余重金属受到扩散作用控制,且各重金属释放速率呈现钡<钴<锌<锰<镍<铬<砷<铅<铜的规律。结论 油基岩屑脱油残渣可替代矿粉,用于制备沥青面层试块,制备的沥青面层试块重金属迁移污染地...     

Self-Powered Electrically Controlled Drug Release Systems Based on Nanogenerator

Precision medicine requires precise regulation of drugs in terms of time, space, and dosage. Exogenous control systems, such as electrical responsiveness, have made great progress. However, wearable or implantable controlled drug release devices still face major challenges due to limitations including limited battery life, large size, and fixed power supply. To overcome these limitations, the fabrication of autonomous devices is available to endure extended periods without reliance on external power sources. As a promising strategy, nanogenerators (NGs) turn body mechanical energy into electricity, powering long-term drug release. In this review, the current status of drug delivery systems (DDS) is briefly outlined and the importance of self-driven controlled drug release systems is emphasized. The main types and operational mechanisms of various nanogenerators are introduced. This review also focuses on summarizing the latest progress of self-powered controlled drug release systems based on nanogenerators (NG-based CDRs). Additionally, their applications in the field of drug release are introduced in detail. Finally, the existing challenges and future trends of self-powered NG-based CDRs are discussed from the perspectives of clinical needs and practical translation.     

Sustainable Stabilizer-Free Nanoparticle Formulations of Valsartan Using Eudragit® RLPO

The bioavailability of the antihypertensive drug valsartan can be enhanced by various microencapsulation methods. In the present investigation, valsartan-loaded polymeric nanoparticles were manufactured from Eudragit^® RLPO using an emulsion–solvent evaporation method. Polyvinyl alcohol (PVA) was found to be a suitable stabilizer for the nanoparticles, resulting in a monodisperse colloid system ranging in size between 148 nm and 162 nm. Additionally, a high encapsulation efficiency (96.4%) was observed. However, due to the quaternary ammonium groups of Eudragit^® RLPO, the stabilization of the dispersion could be achieved in the absence of PVA as well. The nanoparticles were reduced in size (by 22%) and exhibited similar encapsulation efficiencies (96.4%). This more cost-effective and sustainable production method reduces the use of excipients and their expected emission into the environment. The drug release from valsartan-loaded nanoparticles was evaluated in a two-stage biorelevant dissolution set-up, leading to the rapid dissolution of valsartan in a simulated intestinal medium. In silico simulations using a model validated previously indicate a potential dose reduction of 60–70% compared to existing drug products. This further reduces the expected emission of the ecotoxic compound into the environment.     

复杂井况下短轻尾管丢手技术研究与应用

尾管固井发生丢手失败会造成重大损失,严重时会导致油井报废。对于超深井、大斜度井中的短轻尾管固井,由于尾管短,浮重轻,摩阻大,丢手判断和丢手都非常困难,发生丢手失败的风险很大。研究了一套在超深井、大斜度井等复杂井况下,有效保证短轻尾管丢手成功的工艺技术,对降低短轻尾管固井施工风险,节约钻井成本具有重要意义。在分析影响尾管固井丢手因素的基础上,分析了非常规短尾管固井技术的适用性,提出了一整套有效保证短轻尾管固井丢手成功的技术措施,并以TP188X井短轻尾管固井施工为例,介绍了该井的丢手判断施工过程。对复杂情况下短轻尾管固井的安全操作具有指导作用。