全牙列牙合垫结合弹性吊颌帽治疗替牙期下颌骨髁状突骨折

目的：探讨全牙列牙合垫式保持器及吊颌帽弹性牵引在替牙期儿童髁状突骨折治疗的价值。方法：选取19例替牙期下颌骨髁状突骨折合并上颌前牙外伤性松动的患者,用全牙列牙合垫式保持器结合吊颌帽弹性牵引进行治疗。结果：所有患儿松动牙固定良好,咬合关系正常,无张口受限。X线片骨折复位良好。结论：全牙列牙合垫式保持器结合吊颌帽弹性牵引是一种治疗替牙期儿童下颌骨髁状突状突骨折的有效方法。     

弹性髓内钉治疗儿童胫骨干骨折

2010年3月～2013年4月,我院应用弹性髓内钉（elastic stable intramedul-lary nailing,ESIN）治疗35例儿童胫骨干骨折患儿,疗效满意,报道如下。     

Mechanics of bacteriophage maturation

Capsid maturation with large-scale subunit reorganization occurs in virtually all viruses that use a motor to package nucleic acid into preformed particles. A variety of ensemble studies indicate that the particles gain greater stability during this process, however, it is unknown which material properties of the fragile procapsids change. Using Atomic Force Microscopy-based nano-indentation, we study the development of the mechanical properties during maturation of bacteriophage HK97, a λ-like phage of which the maturation-induced morphological changes are well described. We show that mechanical stabilization and strengthening occurs in three independent ways: (i) an increase of the Young's modulus, (ii) a strong rise of the capsid's ultimate strength, and (iii) a growth of the resistance against material fatigue. The Young's modulus of immature and mature capsids, as determined from thin shell theory, fit with the values calculated using a new multiscale simulation approach. This multiscale calculation shows that the increase in Young's modulus isn't dependent on the crosslinking between capsomers. In contrast, the ultimate strength of the capsids does increase even when a limited number of cross-links are formed while full crosslinking appears to protect the shell against material fatigue. Compared to phage λ, the covalent crosslinking at the icosahedral and quasi threefold axes of HK97 yields a mechanically more robust particle than the addition of the gpD protein during maturation of phage λ. These results corroborate the expected increase in capsid stability and strength during maturation, however in an unexpected intricate way, underlining the complex structure of these self-assembling nanocontainers.     

Variable selection for discrete survival model with frailty in presence of left truncation and right censoring: Studying association of environmental toxicants on time-to-pregnancy

Understanding the association between mixtures of environmental toxicants and time-to-pregnancy (TTP) is an important scientific question as sufficient evidence has emerged about the impact of individual toxicants on reproductive health and that individuals are exposed to a whole host of toxicants rather than an individual toxicant. Assessing mixtures of chemical effects on TTP poses significant statistical challenges, namely (i) TTP being a discrete survival outcome, typically subject to left truncation and right censoring, (ii) chemical exposures being strongly correlated, (iii) appropriate transformation to account for some lipid-binding chemicals, (iv) non-linear effects of some chemicals, and (v) high percentage of concentration below the limit of detection (LOD) for some chemicals. We propose a discrete frailty modeling framework (named Discnet) that allows selection of correlated covariates while appropriately addressing the methodological issues mentioned above. Discnet is shown to have better and stable false negative and false positive rates compared to alternative methods in various simulation settings. We did a detailed analysis of the pre-conception endocrine disrupting chemicals and TTP from the LIFE study and found that older females, female exposure to cotinine (smoking), DDT conferred a delay in getting pregnant, which was consistent across various approaches to account for LOD as well as non-linear associations.     

硬化大脑中动脉及豆纹支管壁弹性结构改变及意义

本文用光镜、电镜观察了正常和硬化大脑中动脉及其豆纹支管壁弹性结构的形态。结果显示，硬化大脑中动脉内弹力膜断裂，且以外层断裂明显，波纹状外观消失；而豆纹支内弹力膜结构完整，波纹状外观清晰可见。平滑肌萎缩、变性，胶原纤维增多。提示硬化大脑中动脉破裂出血是内弹力膜破坏，平滑肌萎缩，管壁脆性增加所致；而豆纹动脉是根部存在＂中膜缺损＂，此外受血流冲击引起破裂的可能性大。     

单根弹性髓内针治疗跖骨颈骨折

正2012年1月~2014年12月,我们采用单根钛制弹性髓内针治疗10例跖骨颈骨折患者,取得良好疗效,报道如下。1材料与方法1.1病例资料本组10例,男7例,女3例,年龄18~52岁。左足6例,右足4例。均为第2~4跖骨颈闭合骨折,简单骨折7例,粉碎性骨折3例;单发跖骨颈骨折2例,多段跖骨颈骨折8例。受伤至手术时间2~7 d。     

Assessing mechanical function of the zygomatic region in macaques: validation and sensitivity testing of finite element models

Crucial to the interpretation of the results of any finite element analysis of a skeletal system is a test of the validity of the results and an assessment of the sensitivity of the model parameters. We have therefore developed finite element models of two crania of Macaca fascicularis and investigated their sensitivity to variations in bone material properties, the zygomatico-temporal suture and the loading regimen applied to the zygomatic arch. Maximum principal strains were validated against data derived from ex vivo strain gauge experiments using non-physiological loads applied to the macaque zygomatic arch. Elastic properties of the zygomatic arch bone and the zygomatico-temporal suture obtained by nanoindentation resulted in a high degree of congruence between experimental and simulated strains. The findings also indicated that the presence of a zygomatico-temporal suture in the model produced strains more similar to experimental values than a completely separated or fused arch. Strains were distinctly higher when the load was applied through the modelled superficial masseter compared with loading an array of nodes on the arch. This study demonstrates the importance of the accurate selection of the material properties involved in predicting strains in a finite element model. Furthermore, our findings strongly highlight the influence of the presence of craniofacial sutures on strains experienced in the face. This has implications when investigating craniofacial growth and masticatory function but should generally be taken into account in functional analyses of the craniofacial system of both extant and extinct species.     

Closed/open reduction and titanium elastic nails for severely displaced proximal humeral fractures in children

Purpose

The aim of the study was to evaluate the clinical outcome of closed/open reduction and titanium elastic nails (TENs) in children with severely displaced proximal humeral fractures.

Methods

A retrospective study was performed on 37 children suffering from proximal humeral fracture between April 2009 and July 2012. All these patients were treated by closed or open reduction with TEN fixation. The healing process was assessed by radiographic and clinical follow-up for up to 36 months. Radiographic assessment was performed on the scheduled follow-ups to examine fracture healing, remodelling, bone growth and residual deformity. The clinical outcomes were evaluated using the Neer shoulder score and patients’ satisfaction report at the final follow-up. Complications related to the treatment were also recorded.

Results

All patients had a mean follow-up period of 24 months (12–36) after surgery. All fractures were healed, radiologically, at a median time of eight weeks (seven to ten weeks). There were no major complications related to the treatment. Two patients complained about skin irritation around the sides of the prominent distal ends of the nails. Implant removal took place at an average of 5.8 months post-operatively as an outpatient procedure. There were no observed complications in association with the removal of the hardware. At the final follow-up, the mean Neer shoulder score was 96.65 (range 83–100). Thirty patients were very satisfied with their surgical outcomes and the remaining seven were satisfied. Function of the affected arm returned to normal at the end of the follow-up period in all cases.

Conclusions

Combining closed or open reduction with TEN fixation is recommended for treating severely displaced proximal humeral fractures in children. Our data showed evidence of satisfactory outcomes with a low complication rate and a fast return to normal mobility of the affected arms.     

钛制弹性髓内钉内固定治疗肱骨近端骨折的初步观察

目的 探讨钛制弹性髓内钉内固定治疗成人不稳定肱骨近端骨折的可行性及疗效。方法 回顾性分析自2009-06-2012-12采用钛制弹性髓内钉内固定治疗的42例成人肱骨近端骨折的临床资料。结果 本组42例平均随访17.2个月（10-30个月）。平均手术时间28 min（20-60 min）,平均出血量45 ml（20-100 ml）。骨折均获愈合,平均愈合时间为8.8周（6-12周）。末次随访时,VAS疼痛评分平均0.7分（0-4分）;Constant-Murley绝对值评分平均86.7分（68-100分）,优17例,良20例,可4例,差1例,优良率88.1%。未发生神经血管损伤、感染、骨折不愈合及肱骨头坏死等并发症。结论采用钛制弹性髓内钉内固定治疗成人肱骨近端骨折效果良好,具有创伤轻微、固定可靠、并发症少等优点,适用于肱骨外科颈骨折以及部分合并大结节骨折的3部分骨折。     

Grain-to-Grain Interaction Effect in Polycrystalline Plain Low-Carbon Steel within Elastic Deformation Region

A grain is surrounded by grains with different crystal orientations in polycrystalline plain low-carbon steel. The grain is constrained by its adjacent grains in the tension process. The interaction of the grain with the adjacent grains was investigated within the elastic deformation region. The following results have been obtained: (1) the Young’s modulus of a grain without consideration of grain-to-grain interaction is denoted as the inherent Young’s modulus; when the inherent Young’s modulus of a grain is equal to the Young’s modulus of the bulk material, there is almost no interaction between the grain and its adjacent grains; when a grain has a great difference between its inherent Young’s modulus and the Young’s modulus of the bulk material, its grain-to-grain interactions increase significantly; (2) the grain-to-grain interaction is mainly caused by the difference in the inherent Young’s modulus between the grain and its adjacent grains; the misorientation angle between the grain and its adjacent grains has almost no effect on the grain-to-grain interaction.