Real-time-guided bone regeneration around standardized critical size calvarial defects using bone marrow-derived mesenchymal stem cells and collagen membrane with and without using tricalcium phosphate: an in vivo microcomputed tomographic and histologic e

The aim of the present real time in vivo micro-computed tomography （pCT） and histologic experiment was to assess the efficacy of guided bone regeneration （GBR） around standardized calvarial critical size defects （CSD） using bone marrow-derived mesenchymal stem cells （BMSCs）, and collagen membrane （CM） with and without tricalcium phosphate （TCP） graft material. In the calvaria of nine female Sprague-Dawley rats, full-thickness CSD （diameter 4.6 mm） were created under general anesthesia. Treatment-wise, rats were divided into three groups. In group 1, CSD was covered with a resorbable CM; in group 2, BMSCs were filled in CSD and covered with CM; and in group 3, TCP soaked in BMSCs was placed in CSD and covered with CM. All defects were closed using resorbable sutures. Bone volume and bone mineral density of newly formed bone （NFB） and remaining TCP particles and rate of new bone formation was determined at baseline, 2, 4, 6, and 10 weeks using in vivo pCT. At the lOth week, the rats were killed and calvarial segments were assessed histologically. The results showed that the hardness of NFB was similar to that of the native bone in groups I and 2 as compared to the NFB in group 3. Likewise, values for the modulus of elasticity were also significantly higher in group 3 compared to groups 1 and 2. This suggests that TCP when used in combination with BMSCs and without CM was unable to form bone of significant strength that could possibly provide mechanical ＂lock＂ between the natural bone and NFB. The use of BMSCs as adjuncts to conventional GBR initiated new bone formation as early as 2 weeks of treatment compared to when GBR is attempted without adiunct BMSC therapy.

Porous titanium granules in critical size defects of rabbit tibia with or without membranes

Recently, porous titanium granules （PTGs） have been indicated for the preservation of the dimensions of post-extraction sockets, as a filler in sinus lift procedures and for the treatment of peri-implant and periodontal defects, based on the osteoconductivity and dimensional stability of the titanium granules. However, there is a lack of information regarding the use of this material in larger defects and in conjunction with membranes. The objective of this study is to test the behavior of PTGs used to fill critical size defects in rabbit tibiae, with and without membranes. Critical defects were created in both tibiae of rabbits, divided randomly into three groups： Group A （defect filled with PTG）, Group B （defect filled with PTG＋collagen membrane） and a control group （empty defect）. After six weeks, histomorphometric analysis was performed. The results showed more defect closures at the cortical area （87.37%±2.2%） and more bone formation at the marrow area （57.6%± 1.3%） in Group B, in comparison with the other groups （P〈0.05）; the use of membranes improved the material stability expressed as more percentages of the original material when membranes were used （P〈0.05）. Finally, inflammatory reactions were observed when the granules were not protected by membranes. In spite of the limitations of this animal study, it may be concluded that PTG particles are osteoconductive and allow bone growth. The PTG particles must be covered by a membrane, especially when grafting larger defects, in order to control particle migration, promote clot stabilization and separate the PTG graft from undesired soft tissue cells.

Bauschinger and size effects in thin-film plasticity due to defect-energy of geometrical necessary dislocations

The Bauschinger and size effects in the thinfilm plasticity theory arising from the defect-energy of geometrically necessary dislocations （GNDs） are analytically investigated in this paper. Firstly, this defect-energy is deduced based on the elastic interactions of coupling dislocations （or pile-ups） moving on the closed neighboring slip plane. This energy is a quadratic function of the GNDs density, and includes an elastic interaction coefficient and an energetic length scale L. By incorporating it into the work- conjugate strain gradient plasticity theory of Gurtin, an energetic stress associated with this defect energy is obtained, which just plays the role of back stress in the kinematic hardening model. Then this back-stress hardening model is used to investigate the Bauschinger and size effects in the tension problem of single crystal Al films with passivation layers. The tension stress in the film shows a reverse dependence on the film thickness h. By comparing it with discrete-dislocation simulation results, the length scale L is determined, which is just several slip plane spacing, and accords well with our physical interpretation for the defect- energy. The Bauschinger effect after unloading is analyzed by combining this back-stress hardening model with a friction model. The effects of film thickness and pre-strain on the reversed plastic strain after unloading are quantified and qualitatively compared with experiment results.

Early therapeutic effect of platelet-rich fibrin combined with allogeneic bone marrow-derived stem cells on rats’ critical-sized mandibular defects

BACKGROUND Critically sized bone defects represent a significant challenge to orthopaedic surgeons worldwide.These defects generally result from severe trauma or resection of a whole large tumour.Autologous bone grafts are the current gold standard for the reconstruction of such defects.However,due to increased patient morbidity and the need for a second operative site,other lines of treatment should be introduced.To find alternative unconventional therapies to manage such defects,bone tissue engineering using a combination of suitable bioactive factors,cells,and biocompatible scaffolds offers a promising new approach for bone regeneration.AIM To evaluate the healing capacity of platelet-rich fibrin(PRF)membranes seeded with allogeneic mesenchymal bone marrow-derived stem cells(BMSCs)on critically sized mandibular defects in a rat model.METHODS Sixty-three Sprague Dawley rats were subjected to bilateral bone defects of critical size in the mandibles created by a 5-mm diameter trephine bur.Rats were allocated to three equal groups of 21 rats each.Group I bone defects were irrigated with normal saline and designed as negative controls.Defects of group II were grafted with PRF membranes and served as positive controls,while defects of group III were grafted with PRF membranes seeded with allogeneic BMSCs.Seven rats from each group were killed at 1,2 and 4 wk.The mandibles were dissected and prepared for routine haematoxylin and eosin(HE)staining,Masson's trichrome staining and CD68 immunohistochemical staining.RESULTS Four weeks postoperatively,the percentage area of newly formed bone was significantly higher in group III(0.88±0.02)than in groups I(0.02±0.00)and II(0.60±0.02).The amount of granulation tissue formation was lower in group III(0.12±0.02)than in groups I(0.20±0.02)and II(0.40±0.02).The number of inflammatory cells was lower in group III(0.29±0.03)than in groups I(4.82±0.08)and II(3.09±0.07).CONCLUSION Bone regenerative quality of critically sized mandibular bone defects in rats was better promoted by PRF membranes seeded with BMSCs than with PRF membranes alone.

Effects of Imperfect Quality and Defective Items on Economic Production Lot Size

The classical EPQ model has been used for a long ti me and is widely accepted and implemented. Nevertheless, the analysis for finding an economic lot size has based on a number of unrealistic assumptions. A common unrealistic assumption in using EPQ is that all units produced are of good quali ty. The classical EPQ model shows that the optimal lot size will generate minimum ma nufacturing cost, thus producing minimum setup cost and inventory cost. However, this is only true if all products manufactured in the process are assumed to be of good quality (i.e. all products are within the specification limits). In rea lity this is not the case, therefore, it is necessary to consider the cost of im perfect quality items, because this cost can influence the economic lot size. Ma ny studies and recent papers have indicated that there is a significant relation ship between economic production lot size and process/product quality. However, their models included either the imperfect quality items (not necessarily de fective) which are to be sold at a discounted price or defective items which can be reworked or rejected. The aim of this paper is to provide a framework to integrate three different sit uations (discounted pricing/rework/reject) into a single model. 100% inspection is performed in order to distinguish the amount of good quality items, imper fect quality items and defective items in each lot. In this paper, a mathematica l model is developed, and a numerical example is presented to illustrate the sol ution procedures. It is found that the economic production lot size tends to inc rease as the average percentage of imperfect quality items and defectives (rejec ted items) increases.

Successive defects asymmetric simple exclusion processes with particles of arbitrary size

This paper uses various mean-field approaches and the Monte Carlo simulation to calculate asymmetric simple exclusion processes with particles of arbitrary size in the successive defects system. In this system, the hopping probability p （p 〈 1） and the size d of particles are not constant, Through theoretical calculation and computer simulation, it obtains the exact theoretical results and finds that the theoretical results are in agreement with the computer simulation. These results are helpful in analysing the effect of traffic with different hopping probabilities p and sizes d of particle.

Healing Mechanism and Osteogenic Capacity of Bovine Bone Mineral—Human Amniotic Mesenchymal Stem Celland Autogenous Bone Graft in Critical Size Mandibular Defect

Experiments on maxillofacial bone tissue engineering showed the promising result;however, its healing mechanisms and effectiveness had not been fully understood. The aim of this study is to compare the bone healing mechanism and osteogenic capacity between bovine bone mineral loaded with hAMSC and autogenous bone graft in the reconstruction of critical size mandibular bone defect. Critical size defects were made at the mandible of 45 New Zealand white rabbits reconstructed with BBM-hAMSC, BBM alone, and ABG, respectively. At the end of first, second, and twelfth weeks, five rabbits from each experimental week were sacrificed for histology and immunohistochemistry staining. Expressions of vascular endothelial growth factor (VEGF), bone mor-phogenic proteins-2 (BMP2), Runx2 and the amount of angiogenesis were analyzed in the first and second week groups, while expressions of Runx2, osteocalcin, collagen type-I fibres, trabecular area and bone incorporation were analyzed in the twelfth week groups. The result showed that expressions of VEGF, BMP2 and Runx2 as well as the amount of angiogenesis were higher in ABG compared with BBM-hAMSC group in the first and second weeks of healing. The result of twelfth week of healing showed that expressions of Runx2 and osteocalcin as well as the thickness of collagen type-I fibres were significantly higher in BBM-hAMSC compared to ABG group, while there was no statistically difference in trabecular area and bone incorporation between BBM-hAMSC and ABG group. This study concluded that early healing activities were higher in auto-genous bone graft than in BBM-hAMSC, while osteogenic activities in the late stage of healing were higher in BBM-hAMSC compared to autogenous bone graft. It was also concluded that the osteo-genic capacity of BBM-hAMSC was comparable to autogenous bone graft in the reconstruction of critical size defect in the mandible.

高纯度横波蝶形线圈电磁超声换能器优化设计

蝶形线圈电磁超声换能器(EMAT)能够在铝块中同时激发出超声横波和纵波,接收信号中存在横波反射回波和纵波反射回波,纵波回波会影响缺陷检测的准确性。该文设计了一种变尺寸蝶形线圈EMAT,通过改变线圈不同位置导线的宽度与间距,改变不同位置的换能效率,以实现横波的增强和纵波的抑制。首先,考虑永磁体的空间磁场分布,分析蝶形线圈EMAT不同位置导线所受洛伦兹力与激发超声波类型的关系,结合有限元声场云图,得到EMAT接收信号中存在多个回波的原因;其次,研究线圈参数对换能效率和横波纵波幅值比的影响规律,利用有限元仿真确定变尺寸EMAT的设计参数;最后,制备常规与变尺寸蝶形线圈EMAT,采集无缺陷铝合金试块的回波,结果表明,当永磁体直径与线圈中心宽度比为1.92时,纵波幅值削弱了66.1%,横波幅值增大了36.3%,横纵波幅值比从5.8升至23.1。该文设计的变尺寸蝶形线圈EMAT实现了对纵波的削弱和横波的增强,提升了横波电磁超声内部缺陷检测的可靠性。

股骨骨缺损动物模型制备现状及特点

背景:骨缺损的修复及后期临床转归仍是临床研究中的热点和难点,是困扰临床医师的常见问题。构建合适、可重复性及无限接近临床的动物实验模型及科学的评估对进一步的临床治疗相关疾病至关重要。目的:回顾性分析文献中股骨骨缺损常用实验动物模型制备方法及不同模型特点,评估优势与不足,为相关研究者选择合适的股骨骨缺损动物模型提供一定的参考。方法:检索PubMed、Web of Science、Medline数据库及CNKI数据库,设定英文检索词为:bone defect,bone,bones,defect,defects,defective,animal model,animal,model,laboratory,laboratory animal,animal laboratory;中文检索词为:骨缺损,动物模型,实验。检索时限为2000-01-01/2022-08-01。结果与结论:①对入选的27篇随机对照动物实验进行了分析和评估,实验动物包含大鼠、小鼠、新西兰兔及羊,骨缺损类型主要包含圆柱形骨缺损和节段性截骨骨缺损,部位以股骨中段及远端居多。多用于评估骨修复材料、药物、载药活性物质及物理治疗等方法对骨缺损修复的影响及缺损愈合机制研究,尤其是负重骨缺损修复机制的研究。②不同缺损类型及不同实验动物股骨骨缺损值的范围不同,研究者可结合实验目的,选择合适的动物及骨缺损类型,并设置合理的骨缺损值。③目前的研究表明,股骨骨缺损模型以圆柱形及节段截骨骨缺损为主,主要是在股骨远端及中段,手术方法及术后处理较为成熟,可操作性强,能够提供成熟的实验动物模型。④就圆柱形骨缺损而言,大鼠及新西兰兔更适合,而节段性截骨则无特殊要求,各种动物均能满足实验要求。

红外无损检测缺陷尺寸测量方法研究

红外无损检测技术可有效检测金属、非金属、复合材料的内部缺陷,缺陷尺寸是评估缺陷影响的关键参数,本文以半宽高测量算法来实现对缺陷尺寸的半自动测量,首先手动绘制过缺陷中心的直线构成空间像素曲线,采用Savitzky-Golay滤波算法滤波,并自动寻找空间像素曲线半宽高位置,从而实现对缺陷尺寸的测量。通过对塑料试件、碳钢试件、碳纤维复合材料试件研究发现,不同时刻红外图像测量出的缺陷尺寸具有不同的误差,采用清晰时刻红外图像,测量误差在10%内,采用模糊时刻红外图像,测量误差在20%左右,相对于传统手动测量缺陷尺寸,本文方法将有效提高缺陷尺寸测量的精度。

膜诱导技术结合Ca(OH)_(2)-PMMA治疗节段性骨缺损的研究进展

节段性骨缺损是一种负担较大、治疗具有挑战性的疾病,其病因包括创伤、感染、肿瘤等。目前骨缺损的重建方法主要有血管化骨移植、骨搬运以及膜诱导技术(Masquelet技术)等。而血管化自体骨移植虽然被认为是重建大尺寸骨缺损的金标准,但其具有专业性要求高、治疗周期长、过程复杂等局限性,而膜诱导技术因简单、高效及可靠等特性被广泛应用于骨缺损的治疗。膜诱导技术通过两次手术获取具有生物效应的诱导膜,促进缺损部位新骨的生长和愈合,是目前国内外公认的治疗节段性骨缺损的有效方法。本文将概述骨缺损的现状,介绍临界尺寸骨缺损的概念,探讨及思考在膜诱导技术中结合聚甲基丙烯酸甲酯氢氧化钙混合物[Ca(OH)_(2)-PMMA]新型材料应用于节段性骨缺损治疗的临床意义。

基于工程临界分析法的相控阵超声检测焊缝缺陷定量研究

本文分析了相控阵超声检测对缺陷定量的特点,介绍了相控阵超声采用工程临界分析法(ECA)对缺陷定量的特殊性。通过多种检测方法对焊缝中预制缺陷进行检测和分析,发现采用工程临界分析法定量不仅能合理地分析评定缺陷,还能保证检测结果一致。得出相控阵超声检测采用工程临界分析法对缺陷定量既科学合理,又准确可靠。

FFT和MEM在冲击回波法识别混凝土缺陷尺寸中的对比研究

针对冲击回波法识别混凝土缺陷尺寸的两种信号分析方法,通过理论分析与现场模型试验,研究了FFT(快速傅里叶变换)和MEM(最大熵法)在冲击回波信号处理中的应用,结果表明:FFT算法简单快速,但分析过程添加的窗函数会导致频谱泄露和分辨率降低;MEM算法可以对已知数据外的信号进行合理估计,具有较高的分辨率,更加符合实际工程的要求;频谱图和卓越周期图可以携带缺陷信息,缺陷在FFT计算结果中体现为峰值提前,在MEM计算结果中体现为峰值延后;等值线图可以更加直观地识别缺陷位置,MEM的计算结果比FFT计算结果精度更高。

胶原基骨、天然煅烧骨在大鼠颅骨缺损修复术中的诱导成骨效果对比观察

目的对比观察胶原基骨和天然煅烧骨在大鼠颅骨缺损修复术中的诱导成骨效果。方法18只SD大鼠随机分为3组,每组6只,均建立SD大鼠颅骨双侧临界尺寸骨缺损模型,均行缺损修复术,术中颅骨一侧缺损部位填充胶原基骨(胶原基骨组),另一侧缺损部位填充天然煅烧骨(煅烧骨组)。术后第4、8、12周,取大鼠颅骨双侧缺损部位新生的骨组织,通过Micro-CT方法及病理检查结果评价成骨效果[成骨速度(新生骨骨体积分数、新生骨骨面积分数)、成骨质量(骨小梁数量、厚度、间隙;新生骨组织中纤维结缔组织、新生毛细血管数量)],并比较。结果Micro-CT结果显示,术后第4、8、12周,胶原基骨组的新生骨骨体积分数、骨小梁数量、骨小梁厚度均高于天然煅烧骨组,骨小梁间隙低于煅烧骨组。HE染色结果显示,术后第4、8、12周,与煅烧骨组比较,胶原基骨组的新生骨骨面积分数高。胶原基骨组胶原基骨吸收速度快,新生骨含较多的结缔组织、新生血管,骨质较软;煅烧骨组天然煅烧骨吸收速度慢,新生骨中结缔组织、血管较少,骨质偏硬。结论在大鼠颅骨临界尺寸骨缺损修复术中,胶原基骨诱导成骨的速度较快,成骨量高,吸收快,新生骨组织中结缔组织、新生血管多,新生骨质类似“松质骨”;天然煅烧骨诱导成骨速度较慢,新生骨组织中结缔组织、新生血管少,新生骨质类似“皮质骨”。

林场不同树种选育对PM_(2.5)大气颗粒物的调控研究

为了降低PM_(2.5)大气颗粒物含量,研究林场不同树种选育对PM_(2.5)大气颗粒物的调控效果。文章采集某区域6种园林植物叶表面空气微粒、叶中元素的组成、含量以及再悬浮速率,并对植物叶片滞尘能力测定方法进行优化,构建空气质量浓度与气象要素关系调控模型。通过检测不同样本叶片蜡质层对颗粒物的截留能力、滞尘粒度分布曲线的变化趋势、以及叶片滞留尘埃的平均颗粒大小,通过拟合计算获取不同树种选育对PM_(2.5)大气颗粒物的调控效果。单叶面积小且叶表粗糙的林场植物可以更好地对PM_(2.5)大气颗粒物进行调控。

经纱断头原因浅析

分析织造过程中影响断经的主要原因和解决措施。介绍了原纱质量方面出现竹节、弱捻、细节、异纤、棉结等疵点的特点及成因,针对浆纱过程易产生的轻浆、黏并、浆斑、脆断等问题给出相对应的解决措施。指出:从原料选配、设备状态以及纺专器材使用周期等着手是降低经纱断头的前提条件;浆纱工艺、机械、操作等也对断经有重要影响。认真分析断经产生具体原因,有的放矢地解决和减少织机断经停车,对提高织机效率意义重大。

Fluoride-mediated nano-sized high-silica ZSM-5 as an ultrastable catalyst for methanol conversion to propylene

Fluoride mediated nano-sized ZSM-5 （ZSM-5-F） with a high Si/AI ratio of 181 was fabricated using a seed-induction method and evaluated the catalysis of the methanol to propylene （MTP） reaction. High propylene selectivity （45%） was similar to ZSM-5-OH synthesized via a hydroxide route. However, ZSM- 5-F showed much longer lifetime （305 h） compared with ZSM-5-OH （157 h） in spite of similar crystal size and aluminum content. Characterization by NH3-TPD. Py-IR, OH-IR, SEM, TG-DTA, XRD and 1H MAS NMR techniques indicated that the enhanced catalytic performance of ZSM-S-F is attributed to the fewer structural defects in the form of internal silanol groups and silanol nests.

Quantitative Evaluation of Fatigue Crack Size Using Eddy Current Pulsed Thermography

A set of metallic specimens containing fatigue cracks with different sizes were tested using eddy current pulsed thermography(ECPT),therefore the relations between heating response of the crack area and the crack length was studied.The numerical and experimental results both showed that the increase of the crack length enhanced the crack heating response under specific test conditions.A particular form of calculated response signal,which is linearly related to the crack length,was introduced to provide a quantitative evaluation of crack length.

氮化镓/石墨烯/碳化硅异质界面热输运特性的分子动力学研究

为了探究氮化镓/石墨烯/碳化硅异质界面热输运特性,采用非平衡分子动力学方法从温度、尺寸以及空位缺陷三个方面研究其对界面热导的影响,通过声子态密度和声子参与率对界面热导的变化进一步阐述分析.研究表明:温度升高使界面热导增大,分析认为随着温度升高晶格振动加剧,低频声子态密度变大,参与热输运声子数量增加;其中单层石墨烯层结构界面热导的改变要高于多层石墨烯结构的界面热导.当热输运方向的结构尺寸变化时,同时改变氮化镓和碳化硅的层数,界面热导无明显变化,界面热输运声子散射几乎不受影响;但中间石墨烯层从1层增加至5层时,界面热导率先减小后缓慢增大,由于在4层时低频声子参与率变小,更多的声子局域化,不参与传热声子数量更多,故界面热导到达最小值0.021 GW/(m^(2)·K).随空位缺陷浓度增加界面热导先逐步增大后减小,区别在于单空位缺陷在浓度为10%时,界面热导达到最大值0.064 GW/(m^(2)·K);而双空位缺陷在浓度为12%时,界面热导率达到最大值0.065 GW/(m^(2)·K),分析认为更多的声子从局域进入离域,参与该传热声子较多,导致界面热导增大.研究结果有助于调控氮化镓器件的热输运性能,可以为异质界面器件的设计提供理论依据.

弯管缺陷尺寸与位置对超声波传播特性影响

基于超声数值模拟,研究椭圆形冲蚀缺陷的几何尺寸和位置与接收端超声波能量之间的关系。通过控制椭圆形冲蚀缺陷几何尺寸,研究缺陷在弯管θ=0°且Ψ=20°位置处,不同几何尺寸的缺陷对接收端压电传感器(PZT)时域信号能量的影响。此外,为研究相同几何尺寸的椭圆形冲蚀缺陷位于弯管不同位置时,对接收端时域信号能量的影响,椭圆形冲蚀缺陷位于弯管以下位置:Ψ=20°且取值范围为0°-30°,每间隔2.5取一个值;θ=0°且Ψ取值范围为15°-45°,每间隔2.5°取一个值。数值模拟结果表明:缺陷位于弯管θ=0°且Ψ=20°位置处,随着缺陷面积增加,接收端上侧PZT时域信号能量减少;随着缺陷深度和缺陷深度与面积都增加的两种情况下,上侧PZT时域信号能量均出现先减小,当缺陷深度达到弯管厚度的75%(6 mm)时,上侧PZT时域信号能量再增加;相同几何尺寸的缺陷位于弯管θ=0°,随着增加,上侧PZT时域信号能量先减小后增加;相同几何尺寸的缺陷位于弯管Ψ=20°,随着θ增加,θ与Esub呈现出单调递增的关系。通过上述结果可知,椭圆形冲蚀缺陷的几何尺寸和位置与接收端时域信号能量之间存在相关性,基于此可通过能量变化实现对缺陷几何尺寸大小和位置的评估。