Application of a hydrodynamic model to microencapsulation by coacervation

The role of the hydrodynamic conditions in determining the characteristics of microcapsules made by coacervation was investigated in this study. The model proposed by Armenante and Kirwan, regarding the mass transfer to microcapsules in a turbulent agitated system, was applied. The working hypothesis was that the microcapsules are formed in microeddies generated by the agitation source. The dimensions of the microeddies, calculated in the vicinity of the agitation source according to Armenante and Kirwan, depend on the physical properties of the liquid medium and are inversely proportional to the power exchanged from the agitation source of the system. The power was determined according to the hydrodynamic rules developed by Rushton et al. The experimental results confirmed the hypothesis of the model. Indeed, a good relationship was found between the calculated size of the microeddies and the measured diameter of the microcapsules. Moreover, the distribution error (the standard deviation of the microcapsule size frequency distribution curve) was found to be proportional to the mean diameter value of the microcapsules and microeddies. This can be explained considering that the microeddies diameter increases by moving away from the agitation source and, consequently, a distribution of microeddies of difference sizes is present in the medium. The distribution error, which represents the difference between the smaller and the larger diameters, is inversely proportional to the exchanged power and, consequently, proportional to the mean diameter.     

局麻药注入蛛网膜下腔的流体力学分析

腰麻或硬腰联合麻醉已成为当前最安全的区域麻酵方式之一。在实施腰麻过程中,通常麻醉医生除了关注药物的比重以外。很少有人研究腰麻的注药会对麻醉效果产生影响。腰麻中。麻醉的起效时间．局麻药作用时间、麻醉平面的高低等,除了与药物的比重有很大关系外,还与腰麻穿刺针孔的朝向、注药的速度．脑脊液的性质．以及间断或持续注入等有极大的关系。如果在了解这些影响因素时引入流体力学的概念,来说明注入药物对麻醉效果的影响,并寻找一定的规律,对指导腰麻的实施将会有很大帮助。     

流体力学分析说话瓣膜对下颌骨缺损重建患者气管切开后功能恢复的影响

目的运用流体力学的方法,研究佩戴说话瓣膜（SV）对围术期气管切开下颌骨缺损重建患者误吸、口腔分泌物、嗅觉及发音的影响。 方法根据纳入标准及排除标准入组的8例患者按随机数字表法随机分成瓣膜组及对照组。瓣膜组予术后第2天佩戴SV,对照组不予佩戴SV,观察患者误吸、口腔分泌物、嗅觉、发音情况。吞咽功能采用染色实验,口腔分泌物采用视觉模拟评分法（VAS）,患者能正确回答易挥发分子的气味即嗅觉功能阳性,能进行简单的言语交流即发音功能阳性。采用锥形束CT（CBCT）扫描,Mimics和Gambit、Fluent软件,三维重建两组患者气道模型和气道流场,应用SPSS 23.0软件对比分析两组间术前、术后咽腔及声门下腔压力的变化,数据结果以中位数（25%值,75%值）表示。 结果两组相比,瓣膜组4例均改善误吸、嗅觉及发音,口腔分泌物明显减少,差异有统计学意义（P<0.05）,对照组术前、术后声门下压分别为101 327.00 Pa（101 326.25,101 327.75）、101 270.00 Pa（101 269.25,101 270.75）;瓣膜组佩戴SV后恢复声门下气压,术前、术后声门下压均为101 327.00 Pa（101 326.25,101 327.75）,差异无统计学意义（P>0.05）。 结论围术期气管切开患者佩戴SV能够减少误吸风险,改善嗅觉功能,此外,恢复患者言语交流能力,缓解患者围术期焦虑,有利于患者顺利度过围术期。因此,下颌骨缺损血管化腓骨复合组织瓣修复重建患者气管切开后运用SV值得推广运用。     

Numerical analysis of the flow characteristics of rotary blood pump

Thrombus formation and hemolysis have been linked to the dynamics of blood flow in rotary blood pumps and ventricular assist devices. Hemolysis occurs as the blood passes through the pump housing, and thrombi develop in stagnation and low-velocity regions. The predicted velocities, pressure, and turbulence quantities from the numerical simulation are used to identify regions of high shear stress and internal recirculation. A nimerical technique is described that simulates the hydrodynamic characteristics of a rotary blood pump with a flow rate of 6 l/min at a rotational speed of 3000 RPM. A computational fluid dynamics (CFD) code, CFX 4, is used to solve the time-dependent incompressible Navier-Stokes equations using a transient finite volume method and three-dimensional structured grids. The simulation utilized the sliding mesh capabilities of this numerical code to model the rotating impeller and examine the effect of blade shape on the hydrodynamic performance of the blood pump in terms of pressure rise, flow rates, and energy losses. The first impeller model has six straight channels; the second impeller has six backward-curved channels. The results for two impeller configurations are presented and discussed. The curvedpump design resulted in higher pressure rise and maximum shear stresses than the straight-channel one. In general the paper demonstrates that CFD is an essential numerical tool for optimizing pump performance with the aim of reducing trauma to the blood cells.     

A comparative study of different release apparatus in generating in vitro–in vivo correlations for extended release formulations

The importance of hydrodynamics in the development of in vitro–in vivo correlations (IVIVCs) for a BCS Class II compound housed in a hydrophilic matrix formulation and for a BCS Class I compound housed in an osmotic pump formulation was assessed. In vitro release data were collected in media simulating the fasted state conditions in the stomach, small intestine and the ascending colon using the USP II, the USP III and the USP IV release apparatuses. Using the data collected with the USP II apparatus, the plasma profiles were simulated and compared with human plasma profiles obtained after administration of the same dosage forms to healthy fasted volunteers. Data obtained with the USP III and USP IV apparatuses were directly correlated with the deconvoluted human plasma profiles. In vitro hydrodynamics affected the release profile from the hydrophilic matrix. For both formulations, based on the values of the difference factor, all three apparatuses were equally useful in predicting the actual in vivo profile on an average basis. Although some hydrodynamic variability is likely with low solubility drugs in hydrophilic matrices, the hydrodynamics of USP II, III and IV may all be adequate as a starting point for generating IVIVCs for monolithic dosage forms in the fasted state.     

流动腔系统的研究进展

流动腔装置广泛用于体外研究流动环境中的细胞力学行为,是研究细胞粘附及应力与生长关系特性的主要手段之一。作者从流动腔系统的分类、数值模拟(包括后向台阶的流动腔数值模拟)、系统构建等三个方面对流动腔系统作一综述。     

利用hBMSCs在生物反应器中构建小口径血管的实验研究

目的采用改进的生物反应器系统,应用人骨髓间充质干细胞(hBMSCs)构建小口径的组织工程血管。方法设计一套血管生物反应器系统,采用有限元方法对组织工程小血管托架材料进行分析,从而设计一套用于构建直径为2mm的小血管托架;收集人的原代骨髓基质干细胞进行体外扩增和培养,选用第3代细胞与聚羟基乙酸酯(PGA)复合后置于血管生物反应器中动态培养;培养4周后,对材料复合物取材,进行大体观察、HE染色、扫描电镜和平滑肌免疫组化等指标检测。结果血管色泽明亮,有一定的弹性,用镊子反复压下血管能够反弹恢复原样;细胞分泌的胶原基质排列较规则,免疫组化结果表明血管含有平滑肌弹性肌动蛋白的成分。结论改进的血管生物反应器能模拟血管的力学环境,并能利用hBMSCs成功构建组织工程化小血管组织。     

Renal corpuscular hydrodynamics: Digital computer simulation

Summary A mathematical model of the renal corpuscle is presented and used to quantify the effect on filtration rate, nephron blood flow and hydrostatic pressure in the glomerular capillaries of variations in: 1. the hydrostatic pressure in Bowman's space; 2. the hydrodynamic resistances of the afferent and efferent arterioles; 3. the ultrafiltration coefficient of the glomerular membrane; 4. the hydrostatic pressure in the peritubular capillaries; 5. the arterial haematocrit and plasma protein concentration. The model is derived from the principle of conservation of mass and volume. Hydrostatic pressure gradients along the glomerular capillaries are neglectec. The hydrodynamic resistances of the afferent and efferent arterioles are assumed to be determined by two independent factors, one being determined by the vascular dimensions, the other by the haematocrit. Blood flow is considered to be related in a linear manner to the hydrostatic pressure decreases along these vessels. The effect of changing the hydrostatic pressure in Bowman's space on nephronGFR was calculated and found to agree with experimental measurements. When corpuscular hydrodynamics are related to variations in the hydrodynamic resistance of the afferent or efferent arteriole it is seen that the change in efferent arteriolar plasma flow accompanying altered nephronGFR is very sensitive to the way in which the change is produced. In contrast changes in glomerular capillary pressure and filtration fraction are insensitive. The calculations indicate that differences measured in nephronGFR between superficial and juxtamedullary nephrons can be explained by assuming that the diameters of the afferent and efferent arterioles of the juxtamedullary nephrons increase in direct proportion to the diameter of the renal corpuscle.     

激光虹膜切开术对角膜内皮细胞所受切应力影响的数值研究

目的研究激光周边虹膜切开术(laser peripheral iridoctomy,LPI)对患者眼内房水流动和角膜内皮细胞所受流体切应力的影响。方法参照文献中的人眼几何数据,在CAD软件中建立三维完整眼球几何模型,并结合有限元软件数值模拟LPI术后房水流动状态以及角膜内皮细胞所受切应力的变化,并对比LPI手术前后虹膜上不同激光开孔位置时角膜内表面切应力的数值结果。结果虹膜上激光孔的位置越靠近瞳孔中心,角膜受到的切应力越小。在激光孔离瞳孔轴距离分别为4.0、4.5、5.0、5.5 mm时,对应角膜内皮受到的最大切应力分别为16.5、25.8、57.0、179.8 m Pa。激光孔在3、6点方位时的切应力最大值比开孔在12点方位时的切应力最大值(56.95 m Pa)分别高出13.7%和4.2%。结论 LPI会改变患者眼内房水流动和角膜内皮细胞所受流体切应力。合适的开孔位置能降低角膜内皮细胞受到的切应力,减少LPI术后患者大泡角膜病变的风险。     

水动力转染技术的应用进展

水动力转染技术是一种快速、方便、高效的外源基因转染方法,是指通过小鼠尾静脉快速注射大体积含有目的基因的生理盐水,从而实现外源目的基因在小鼠体内的高效表达。此方法在肝脏疾病、糖尿病、心肌炎、肾脏疾病和抗肿瘤等实验动物模型的研究以及这些疾病的基因免疫疗法的研究中已有应用。此外,水动力转染技术在对活体动物基因功能、基因调节、蛋白表达以及基因治疗等方面也有广泛应用。