Quantification of the interaction between biomaterial surfaces and bacteria by 3-D modeling

It is general knowledge that bacteria/surface interactions depend on the surface topography. However, this well-known dependence has so far not been included in the modeling efforts. We propose a model for calculating interaction energies between spherical bacteria and arbitrarily structured 3-D surfaces, combining the Derjaguin, Landau, Verwey, Overbeek theory and an extended surface element integration method. The influence of roughness on the interaction (for otherwise constant parameters, e.g. surface chemistry, bacterial hydrophobicity) is quantified, demonstrating that common experimental approaches which consider amplitude parameters of the surface topography but which ignore spacing parameters fail to adequately describe the influence of surface roughness on bacterial adhesion. The statistical roughness profile parameters arithmetic average height (representing an amplitude parameter) and peak density (representing a spacing parameter) both exert a distinct influence on the interaction energy. The influence of peak density on the interaction energy increases with decreasing arithmetic average height and contributes significantly to the total interaction energy with an arithmetic average height below 70 nm. With the aid of the proposed model, different sensitivity ranges of the interaction between rough surfaces and bacteria are identified. On the nanoscale, the spacing parameter of the surface dominates the interaction, whereas on the microscale the amplitude parameter adopts the governing role.     

Into the groove: instructive silk-polypyrrole films with topographical guidance cues direct DRG neurite outgrowth

Instructive biomaterials capable of controlling the behaviour of the cells are particularly interesting scaffolds for tissue engineering and regenerative medicine. Novel biomaterials are particularly important in societies with rapidly aging populations, where demand for organ/tissue donations is greater than their supply. Herein we describe the preparation of electrically conductive silk film-based nerve tissue scaffolds that are manufactured using all aqueous processing. Aqueous solutions of Bombyx mori silk were cast on flexible polydimethylsiloxane substrates with micrometer-scale grooves on their surfaces, allowed to dry, and annealed to impart β-sheets to the silk which assures that the materials are stable for further processing in water. The silk films were rendered conductive by generating an interpenetrating network of polypyrrole and polystyrenesulfonate in the silk matrix. Films were incubated in an aqueous solution of pyrrole (monomer), polystyrenesulfonate (dopant) and iron chloride (initiator), after which they were thoroughly washed to remove low molecular weight components (monomers, initiators, and oligomers) and dried, yielding conductive films with sheet resistances of 124 ± 23 kΩ square^?1. The micrometer-scale grooves that are present on the surface of the films are analogous to the natural topography in the extracellular matrix of various tissues (bone, muscle, nerve, skin) to which cells respond. Dorsal root ganglions (DRG) adhere to the films and the grooves in the surface of the films instruct the aligned growth of processes extending from the DRG. Such materials potentially enable the electrical stimulation (ES) of cells cultured on them, and future in vitro studies will focus on understanding the interplay between electrical and topographical cues on the behaviour of cells cultured on them.     

A novel 3D approach for determination of frontal and coronal plane tibial slopes from MR imaging

Background

The proximal tibia is geometrically complex, asymmetrical, and variable, is heavily implicated in arthrokinematics of the knee joint, and thus a contributor to knee pathologies such as non-contact anterior cruciate ligament injury. Medial, lateral, and coronal tibial slopes are anatomic parameters that may increase predisposition to knee injuries, but the extent to which each contributes has yet to be fully realized. Previously, two-dimensional methods have quantified tibial slopes, but more reliable 3D methods may prove advantageous.

招飞复检中K值引导法对激光角膜屈光手术眼的筛查

目的 在招飞体检中提高对激光角膜屈光手术眼的筛查效率.方法 对参加招飞复检的3400名学生在裂隙灯检查前,行常规角膜曲率检查,对低K值（角膜曲率值）者重点进行角膜裂隙灯检查,并酌情进行角膜厚度和角膜地形图检查;最后结合病史综合鉴定.结果 参加招飞复检的高中生和大学生中,低K值者68例135眼.重点进行裂隙灯检查68例136眼,其中13例25眼角膜表面具有不同程度异常.行角膜地形图检查65例130眼,其中异常者11例21眼.行角膜厚度检查60例120眼,其中角膜厚度异常11例21眼.14例27眼结合相关检查确诊或高度疑似激光角膜屈光矫治眼,筛查阳性率为0.40%.结论 K值引导筛查法针对性强,可明显提高对激光角膜屈光手术眼的筛查效率,值得在招飞体检工作中推广使用.     

准分子激光原位角膜磨镶术治疗非对称角膜近视眼的临床研究

目的：探讨准分子激光原位角膜磨镶术（LASIK）治疗非对称角膜近视眼的方法和应用效果,为临床治疗提供参考。方法：回顾性抽取分析本院于2009年5月至2010年5月的110例（210眼）角膜地形图为非对称或不规则且初次接受LASIK的近视患者分为两组,即按术前等效球镜分为〈-6.00D的低中屈光组,54例（105眼）;〉-6.00D的重屈光度组,56例（105眼）。随访3-12月,比较随访期间两组患者主要指标视力、屈光状态和角膜非球面系数（Q值）变化。结果：随访期间两组内相比,手术后的主要指标视力、屈光状态和角膜非球面系数（Q值）变化均优于手术前,差异有统计学意义（P〈0.05）;两组间相比,低中屈光度组患者的主要指标视力、屈光状态和角膜非球面系数（Q值）变化均优于重屈光度组,差异有统计学意义（P〈0.05）。结论：应用准分子激光原位角膜磨镶术手术非对称角膜近视眼疗效显著,但术后低中屈光度患者的主要指标视力、屈光状态和角膜非球面系数（Q值）变化均明显优于重屈光度患者,此点在临床中值得注意。     

口腔环境下不同时期正畸镍钛弓丝表面摩擦力及表面结构的变化

[目的]探讨口腔环境下镍钛弓丝不同时期表面摩擦力及结构的变化.[方法]在粘结托槽的上颌模具上,分别测量在排齐整平阶段未使用和使用1、2个月的0.014英寸、0.016英寸镍钛圆丝与托槽间的表面摩擦力.扫描电镜观察镍钛圆丝使用前后表面结构及粗糙度.[结果]使用1个月后镍钛弓丝的表面摩擦力比未使用的明显增大(P＜0.05)...     

不同钛表面形貌对人牙龈成纤维细胞生物学行为的影响

目的:良好的种植体颈部软组织封闭是种植体远期成功的重要因素之一。生物封闭的的主要决定因素之一是种植体颈部的表面形貌。本实验的目的是通过比较三种不同的纯钛表面形貌结构对人牙龈成纤维细胞的生物学行为的影响,寻找一种有利于牙龈胶原纤维附着的较理想的种植体颈部表面形貌,为种植体颈部设计提供指导。方法:本研究采用机械加工处理、电化学腐蚀、电化学腐蚀加酸蚀的方法在纯钛金属表面形成三组不同的表面形貌结构;用激光共聚焦显微镜检测其表面粗糙度;扫描电镜观察其表面微观形态并用X射线能谱色散谱仪检测其表面成分;将其与人牙龈成纤维细胞共同培养,MTT法检测表面细胞的增殖情况;细胞计数仪进行表面细胞计数;扫描电镜观察表面细胞的形状及排列。结果:机械加工组表面较光滑,呈浅的等向排列的微沟纹,表面粗糙度Sa为0.8783±0.2578μm;电化学腐蚀组表面略粗糙,呈圆形或椭圆形浅碟状凹,直径约10～15μm,分布均匀,凹内含有散在的小孔,小孔的直径约为1-5μm,表面粗糙度Sa为1.7530±0.3711μm;电化学腐蚀加酸蚀组表面略粗糙,呈圆形或椭圆形浅碟状凹,直径约10～15μm,分布均匀,凹内含有散在的小孔,小孔的直径约为1-5μm,表面见均匀的半球形纳米突起形成,直径约50～100nm,表面粗糙度Sa为1.6763±0.3440μm。表面成分检测显示三组均未有任何污染物在钛表面。牙龈成纤维细胞在各组钛片表面生长良好,形态正常,各组钛片对于细胞没有明显的毒性,生长曲线与正常细胞的生长曲线规律一致。机械加工组表面细胞沿着材料表面微沟纹平行排列,细胞扁平,伸展较差,细胞伸出的伪足较短;电化学腐蚀组表面细胞自由分布,细胞丰满,伸展良好,细胞伸出的伪足较长,有的伪足伸入到邻近凹内;电化学腐蚀加酸蚀组表面细胞丰满,伸展良好,伸出大量伪足,伪足很长,呈细丝状或带状,可伸入到相隔较远的凹孔内,呈悬空样,也可相互交织成网状。结论:电化学腐蚀加酸蚀可在纯钛表面形成均匀分布的直径为10-20μm的凹及直径为1-5μm的孔,凹及孔的表面均匀布满了直径为50-100nm的半球状突起。电化学腐蚀加酸蚀表面促成纤维细胞粘附作用最强。本实验中形成的微米凹、孔形态及半球形纳米形态均有利于成纤维细胞的粘附。电化学腐蚀加酸蚀方法形成的表面是一种较为理想的种植体颈部表面,可以为种植体颈部设计提供指导。     

新型角膜地形图仪观察泪膜稳定性及其与眼表角膜温度的关系

目的探讨眼表角膜温度与泪膜稳定性的关系。方法选取泪液分泌试验(Sch irm erⅠ)结果>10 mm/5 m in的94例患者,根据干眼症状和泪膜破裂时间(BUT)检查结果分为干眼组(n=48)和非干眼组(n=46)。新型角膜地形图仪拍摄泪膜分布图像,红外线温度计测量眼表角膜温度,分析泪膜稳定性与BUT和眼表角膜温度的关系。结果干眼组泪膜稳定性分级显著高于非干眼组(P<0.01)。泪膜稳定性分级与BUT呈显著负相关(r=-0.752,P=0.00)。根据泪膜稳定性分级,0级、Ⅰ级、Ⅱ级和Ⅲ级患者的平均眼表角膜温度分别为(32.386±0.826 2)℃、(34.084±1.373 3)℃、(34.980±1.331 5)℃和(35.709±0.744 9)℃,各级患者眼表角膜温度差异均有统计学意义(均P<0.01)。结论新型角膜地形图仪可反映泪膜的稳定性。眼表角膜温度升高,泪膜稳定性减弱,可能是造成蒸发过强型干眼的因素之一。     

What is new in Chicago Classification version 4.0?

Since publication of Chicago Classification version 3.0 in 2015, the clinical and research applications of high‐resolution manometry (HRM) have expanded. In order to update the Chicago Classification, an International HRM Working Group consisting of 52 diverse experts worked for two years and utilized formally validated methodologies. Compared with the prior iteration, there are four key modifications in Chicago Classification version 4.0 (CCv4.0). First, further manometric and non‐manometric evaluation is required to arrive at a conclusive, actionable diagnosis of esophagogastric junction (EGJ) outflow obstruction (EGJOO). Second, EGJOO, distal esophageal spasm, and hypercontractile esophagus are three manometric patterns that must be accompanied by obstructive esophageal symptoms of dysphagia and/or non‐cardiac chest pain to be considered clinically relevant. Third, the standardized manometric protocol should ideally include supine and upright positions as well as additional manometric maneuvers such as the multiple rapid swallows and rapid drink challenge. Solid test swallows, postprandial testing, and pharmacologic provocation can also be considered for particular conditions. Finally, the definition of ineffective esophageal motility is more stringent and now encompasses fragmented peristalsis. Hence, CCv4.0 no longer distinguishes between major versus minor motility disorders but simply separates disorders of EGJ outflow from disorders of peristalsis.     

Modelling the Influence of Slide Burnishing Parameters on the Surface Roughness of Shafts Made of 42CrMo4 Heat-Treatable Steel

This article presents the results of tests aimed at determining the effect of slide burnishing parameters on the surface roughness of shafts made of 42CrMo4 heat-treatable steel. The burnishing process was carried out using tools with polycrystalline diamond and cemented carbide tips. Before burnishing, the samples were turned on a turning lathe to produce samples with an average surface roughness Ra = 2.6 µm. The investigations were carried out according to three-leveled Hartley’s poly selective quasi D (PS/DS-P: Ha3) plan, which enables a regression equation in the form of a second-order polynomial to be defined. Artificial neural network models were also used to predict the roughness of the surface of the shafts after slide burnishing. The input parameters of the process that were taken into account included the values of pressure, burnishing speed and feed rate. Overall, the burnishing process examined leads to a reduction in the value of the surface roughness described by the Ra parameter. The artificial neural networks with the best regression statistics predicted an average surface roughness of the shafts with R² = 0.987. The lowest root-mean-square error and mean absolute error were obtained with all the network structures analysed that were trained with the quasi Newton algorithm.