Influence of Implant Surface Topography and Loading Condition on Stress Distribution in Bone Around Implants: A Comparative 3D FEA

A three-dimensional Finite Element Method was used to study the influence of porous coated surface topography of an implant on stress and strain distribution pattern in the cortical and cancellous bone during axial and non-axial loading. Two implants, one with porous surface topography and one with smooth surface were embedded in separate geometric models of posterior mandibular region which was generated using a CT scan data. Material properties and boundary conditions were applied. Load of 100 and 50 N were applied on to the abutment from axial and non-axial directions respectively. Porous surface topography appeared to distribute stress in a more uniform pattern around the implant with near absence of stress in the apical region of implant. Smooth surfaced implant showed high punching stress at the apex of the implant. The porous coated interface was considered to simulate the shock absorbing behavior of periodontal ligament of natural dentition. Maximum amount of stress concentration was observed in the cortical bone which plays a major role in the dissipation of the stress.     

钛表面形貌对人单核细胞活力和粘附影响的实验研究

目的研究钛金属表面形貌对人单核细胞活力和粘附的影响。方法应用机械磨光、酸蚀、喷砂、喷砂酸蚀的表面处理方式形成4种不同的钛片表面形貌,分别设为SiC组、SiC＋F组、63号组和63＋F组。表面粗糙度仪检测钛试件表面粗糙度,以Ra值表征,扫描电镜观测钛试件表面形貌。将离心分离的健康成年人外周血单核细胞接种于处理后钛试件表面,扫描电镜观察培养48 h钛片表面单核细胞粘附情况;四唑盐比色法检测和钛片共同培养1、3、5、7 d的细胞活力。结果 4种钛片表面单核细胞的活力和粘附有差异,置于Ra值最大的63号组培养的单核细胞在第1天、第3天、第5天、第7天都显示了最高的活力,置于Ra值相近的SiC＋F组和63＋F组培养的细胞显示了相似的活力。扫描电镜下观察,表面粗糙的63号组钛片表面粘附了较多的单核细胞,表面多微孔的63＋F组有大量的单核细胞粘附在材料表面的窝洞结构中。结论钛表面形貌影响人单核细胞的活力和粘附。表面粗糙度大促进单核细胞的活力,表面粗糙度大和表面多微孔结构有利于单核细胞的粘附。     

直视下睫状体离断复位术对角膜地形图的影响

目的　探讨传统直视下睫状体离断复位手术前后角膜地形图的变化。方法　收集我院2018年1月至2020年12月因睫状体离断行直视下睫状体离断复位术患者17例（17眼）。所有入选患者术前及术后均行超声生物显微镜(UBM)检查确认睫状体离断及术后复位情况,术前及术后均行Pentacam角膜地形图检查,分析入选患者术前术后角膜地形图相关参数的变化情况。所有入选患者均由同一术者操作下完成直视下睫状体离断复位术。结果　所有患者直视下睫状体离断复位术后UBM检查证实睫状体离断复位;所有术眼术前角膜前表面散光度为（1.24±0.66）D,术后1周为（2.02±1.03）D,差异有统计学意义（P=0.012）。术眼术前角膜前表面变异指数（ISV）为16.29±6.05,术后为27.00±4.69;术眼术前角膜前表面垂直非对称性指数（IVA）为0.12±0.04,术后为0.18±0.05,术眼术前及术后ISV、IVA比较,差异均有统计学意义（均为P<0.001）。角膜前表面7 mm和9 mm环域间的平均曲率术前为（7.97±0.27）mm,术后为（8.05±0.29）mm,差异有统计学意义（P=0.001）。睫状体离断复位手术缝合范围按中位数记录,Pearson相关分析结果显示,睫状体离断复位手术缝合范围中位数与术后散光轴位之间具有显著相关性（r=0.634,P=0.006）。术后1个月,9例患者行Pentacam角膜地形图复查,ISV为17.33±5.74,IVA为0.12±0.05,角膜前表面散光度为（1.02±0.46）D,与术前相比,差异均无统计学意义（均为P>0.05）。结论　经典的直视下睫状体离断复位术可以有效地使睫状体离断复位,但可造成术后早期散光。Pentacam角膜地形图用以评估手术前后患者角膜状态,可为更客观地评估手术效果提供参考。     

Fourier analysis of corneal Scheimpflug imaging: clinical use in keratoconus

AIM: To evaluate the clinical use of Fourier analysis of videokeratography data in the diagnosis and follow-up of keratoconus (KC). METHODS: We conducted a chart review of consecutive patients presented to our cornea clinic. A team of two experienced cornea specialists divided the patients into three groups: normal cornea, forme fruste KC (FFKC), and clinical KC. The exclusion criteria were a history of previous ocular surgery, any accompanying corneal pathology other than KC, high myopia (>6.00 diopters), amblyopia, pregnancy, breastfeeding, or any current autoimmune disease. The data of Fourier series harmonic analysis were evaluated for their diagnostic capacity using the receiver operating characteristic (ROC) curve. A binary logistic regression analysis was also conducted to construct a diagnostic model. A total of 259 eyes showed progression in the clinical KC group and underwent a combination of accelerated corneal collagen cross-linking and topography-guided customized treatment with an excimer laser. RESULTS: The study included 1262 eyes (618 normal, 530 KC, and 114 FFKC) of 1262 patients. We observed that maximum decentration (MaxDec) was almost as good as maximum keratometry (Kmax) in detecting progressive KC. The area under the curve (AUC) was 0.95 for KC [95% confidence interval (CI): 0.93-0.96] and 0.84 for FFKC (95%CI: 0.79-0.88). Higher predictive accuracy was obtained using a model combining the spherical component, MaxDec, irregularity, and regular astigmatism in the center of the cornea (AUC: 0.97; sensitivity: 89%, and specificity: 96%). CONCLUSION: Decentration, Kmax, and posterior radii of curvatures from a 3.0-mm optical zone centered on the thinnest point of the cornea provide the highest accuracy with low reproducibility of Kmax.     

肝硬化的数量化诊断及其影像分型

通过对肝硬化进行量化研究,为临床影像诊断提供依据.选择正常人肝脏横断位CT图片作为对照组,选择肝硬化代偿期组、失代偿期组、肝癌组作为疾病组进行对比研究.利用人体常用解剖轴线作为肝脏测量的基准线.肝脏左叶冠状径(L1)的变化最具有临床意义,肝叶比例不仅存在于肝叶之间也存在于肝叶之内.肝脏各叶测量值对于早期肝硬化的诊断具有重要的意义.     

Quantifying the Mechanical Properties of Materials and the Process of Elastic-Plastic Deformation under External Stress on Material

The paper solves the problem of the nonexistence of a new method for calculation of dynamics of stress-deformation states of deformation tool-material systems including the construction of stress-strain diagrams. The presented solution focuses on explaining the mechanical behavior of materials after cutting by abrasive waterjet technology (AWJ), especially from the point of view of generated surface topography. AWJ is a flexible tool accurately responding to the mechanical resistance of the material according to the accurately determined shape and roughness of machined surfaces. From the surface topography, it is possible to resolve the transition from ideally elastic to quasi-elastic and plastic stress-strain states. For detecting the surface structure, an optical profilometer was used. Based on the analysis of experimental measurements and the results of analytical studies, a mathematical-physical model was created and an exact method of acquiring the equivalents of mechanical parameters from the topography of surfaces generated by abrasive waterjet cutting and external stress in general was determined. The results of the new approach to the construction of stress-strain diagrams are presented. The calculated values agreed very well with those obtained by a certified laboratory VÚHŽ.     

From the Cover: A Middle Eocene lowland humid subtropical “Shangri-La” ecosystem in central Tibet

Tibet’s ancient topography and its role in climatic and biotic evolution remain speculative due to a paucity of quantitative surface-height measurements through time and space, and sparse fossil records. However, newly discovered fossils from a present elevation of ∼4,850 m in central Tibet improve substantially our knowledge of the ancient Tibetan environment. The 70 plant fossil taxa so far recovered include the first occurrences of several modern Asian lineages and represent a Middle Eocene (∼47 Mya) humid subtropical ecosystem. The fossils not only record the diverse composition of the ancient Tibetan biota, but also allow us to constrain the Middle Eocene land surface height in central Tibet to ∼1,500 ± 900 m, and quantify the prevailing thermal and hydrological regime. This “Shangri-La”–like ecosystem experienced monsoon seasonality with a mean annual temperature of ∼19 °C, and frosts were rare. It contained few Gondwanan taxa, yet was compositionally similar to contemporaneous floras in both North America and Europe. Our discovery quantifies a key part of Tibetan Paleogene topography and climate, and highlights the importance of Tibet in regard to the origin of modern Asian plant species and the evolution of global biodiversity.

The Tibetan Plateau, once thought of as entirely the product of the India–Eurasia collision, is known to have had significant complex relief before the arrival of India early in the Paleogene (1–3). This large region, spanning ∼2.5 million km², is an amalgam of tectonic terranes that impacted Asia long before India’s arrival (4, 5), with each accretion contributing orographic heterogeneity that likely impacted climate in complex ways. During the Paleogene, the Tibetan landscape comprised a high (>4 km) Gangdese mountain range along the southern margin of the Lhasa terrane (2), against which the Himalaya would later rise (6), and a Tanghula upland on the more northerly Qiangtang terrane (7). Separating the Lhasa and Qiangtang blocks is the east–west trending Banggong-Nujiang Suture (BNS), which today hosts several sedimentary basins (e.g., Bangor, Nyima, and Lunpola) where >4 km of Cenozoic sediments have accumulated (8). Although these sediments record the climatic and biotic evolution of central Tibet, their remoteness means fossil collections have been hitherto limited. Recently, we discovered a highly diverse fossil assemblage in the Bangor Basin. These fossils characterize a luxuriant seasonally wet and warm Shangri-La forest that once occupied a deep central Tibetan valley along the BNS, and provide a unique opportunity for understanding the evolutionary history of Asian biodiversity, as well as for quantifying the paleoenvironment of central Tibet.^*Details of the topographic evolution of Tibet are still unclear despite decades of investigation (4, 5). Isotopic compositions of carbonates recovered from sediments in some parts of central Tibet have been interpreted in terms of high (>4 km) Paleogene elevations and aridity (9, 10), but those same successions have yielded isolated mammal (11), fish (12), plant (13–18), and biomarker remains (19) more indicative of a low (≤3-km) humid environment, but how low is poorly quantified. Given the complex assembly of Tibet, it is difficult to explain how a plateau might have formed so early and then remained as a surface of low relief during subsequent compression from India (20). Recent evidence from a climate model-mediated interpretation of palm fossils constrains the BNS elevation to below 2.3 km in the Late Paleogene (16), but more precise paleoelevation estimates are required. Further fossil discoveries, especially from earlier in the BNS sedimentary records, would document better the evolution of the Tibetan biota, as well as informing our understanding of the elevation and climate in an area that now occupies the center of the Tibetan Plateau.Our work shows that the BNS hosted a diverse subtropical ecosystem at ∼47 Ma, and this means the area must have been both low and humid. The diversity of the fossil flora allows us to 1) document floristic links to other parts of the Northern Hemisphere, 2) characterize the prevailing paleoclimate, and 3) quantify the elevation at which the vegetation grew. We propose that the “high and dry” central Tibet inferred from some isotope paleoaltimetry (9, 10) reflects a “phantom” elevated paleosurface (20) because fractionation over the bounding mountains allowed only isotopically light moist air to enter the valley, giving a false indication of a high elevation (21).     

New insights into the effects of biomaterial chemistry and topography on the morphology of kidney epithelial cells

Increasing incidence of renal pathology in the western world calls for innovative research for the development of cell‐based therapies such as a bioartificial kidney (BAK) device. To fulfil the multitude of kidney functions, the core component of the BAK is a living membrane consisting of a tight kidney cell monolayer with preserved functional organic ion transporters cultured on a polymeric membrane surface. This membrane, on one side, is in contact with blood and therefore should have excellent blood compatibility, whereas the other side should facilitate functional monolayer formation. This work investigated the effect of membrane chemistry and surface topography on kidney epithelial cells to improve the formation of a functional monolayer. To achieve this, microtopographies were fabricated with high resolution and reproducibility on polystyrene films and on polyethersulfone‐polyvinyl pyrrolidone (PES‐PVP) porous membranes. A conditionally immortalized proximal tubule epithelial cell line (ciPTEC) was cultured on both, and subsequently, the cell morphology and monolayer formation were assessed. Our results showed that L‐dopamine coating of the PES‐PVP was sufficient to support ciPTEC monolayer formation. The polystyrene topographies with large features were able to align the cells in various patterns without significantly disruption of monolayer formation; however, the PES‐PVP topographies with large features disrupted the monolayer. In contrast, the PES‐PVP membranes with small features and with large spacing supported well the ciPTEC monolayer formation. In addition, the topographical PES‐PVP membranes were compatible as a substrate membrane to measure organic cation transporter activity in Transwell® systems. Copyright © 2016 John Wiley & Sons, Ltd.     

The influence of smartphone use on spinal posture – A laboratory study

BackgroundSmartphones have become increasingly more popular and complicated tasks can be performed with these devices. However, the increasing use is associated with shoulder and neck pain, as well as with psychological addiction.Research questionDo different smartphone tasks lead to changes in spinal posture and pelvic position? Is there a relationship between smartphone addiction and changes in posture?MethodsA cross-sectional study including 50 participants was performed. Test subjects completed the Smartphone Addiction Scale and the SF-36 health questionnaire. Subjects spinal posture and pelvic position during different smartphone tasks were measured through a surface topography system. The different tasks were: standing in an upright position, simulating a phone call, texting with one or two hands during standing or while walking on a treadmill. Paired T-tests and ANOVA tests were performed to evaluate differences. The Kendall rank test was used to investigate the association between clinical scores and changes in spinal posture.ResultsAll smartphone tasks lead to a significant increase in thoracic kyphosis and trunk inclination during standing and while walking. A significant increased lumbar lordosis was also found. Texting with one or two hands correlated with increased surface rotation. No associations between smartphone addiction and changes of the spinal posture were reported.SignificanceThis represents the first surface topography study that investigated the influence of different smartphone tasks on the spinal posture and pelvic position during standing and while walking. With the results of this study we demonstrated that smartphone use leads to significant changes of sagittal and frontal spine parameters. Further research should focus on the evaluation of possible detrimental effects of long-term smartphone use on the spinal posture and on the development of preventive measures.