Crystal orientation in the shell of the domestic fowl: An electron diffraction study

Summary The eggshell of the domestic fowl has been studied by transmission electron microscopy and diffraction. Thin sections of shell were prepared by chemical and ion-beam thinning techniques. Each calcite column of the palisade layer consisted of crystallites of diameter 20 to 30 μm with some tendency for crystallite alignment within a single column. Evidence indicates that there was no significant preferred orientation in the palisade layer as a whole. Only in the surface layer was any preferred orientation detected, and here {1014} planes tended to lie parallel to the surface. The results are compared with previously published data, and calcite nucleation and growth are discussed.     

氧化锂含量对牙科云母微晶玻璃析晶性能的影响

目的:研究Li2O对SiO2-Al2O3-MgO-Na2O-K3O-F云母玻璃陶瓷析晶性能、显微结构和抗弯强度的影响.方法:在玻璃基础成分中添加不同含量的Li2O,由差热分析(DTA)曲线确定热处理制度,采用X射线衍射分析(XRD)、扫描电子显微镜(SEM)和三点弯曲强度测试来观测和比较晶体成分、形貌和材料的力学性能.结果:3组玻璃的核化温度为530℃,最适晶化温度随Li2O含量的增加而降低.680℃热处理1 h后,含4%Li2O的母体玻璃析出的云母晶体发育完全,抗弯强度最高(183.82±12.47)MPa.结论:添加一定量的Li2O有助于改善SiO2-Al2O3-MgO-Na2O-K2O-F系云母玻璃陶瓷的析晶性能和力学强度.     

Diffusion tensor imaging of somatosensory tract in cervical spondylotic myelopathy and its link with electrophysiological evaluation

Background and contextAbnormal somatosensory evoked potential (SEP) (ie, prolonged latency) has been associated with poor surgical prognosis of cervical spondylotic myelopathy (CSM).PurposeTo further characterize the extent of microstructural damage to the somatosensory tract in CSM patients using diffusion tensor imaging (DTI).Study design/settingRetrospective study.Patient sampleA total of 40 volunteers (25 healthy subjects and 15 CSM patients).Outcome measuresClinical, electrophysiological, and radiological evaluations were performed using the modified Japanese Orthopedic Association (mJOA) scoring system, SEP, and cord compression ratio in anatomic magnetic resonance (MR) images, respectively. Axial diffusion MR images were taken using a pulsed gradient, spin-echo-echo-planar imaging sequence with a 3-T MR system. The diffusion indices in different regions of the spinal cord were measured.MethodsComparison of diffusion indices among healthy and myelopathic spinal cord with intact and impaired SEP responses were performed using one-way analysis of variance.ResultsIn healthy subjects, fractional anisotropy (FA) values were higher in the dorsal (0.73±0.11) and lateral columns (0.72±0.13) than in the ventral column of white matter (0.58±0.10) (eg, at C4/5) (p<.05). FA was dramatically dropped in the dorsal (0.54±0.16) and lateral columns (0.51±0.13) with little change in the ventral column (0.48±0.15) at the compressive lesions in CSM patients. There were no significant differences in the mJOA scores or cord compression ratios between CSM patients with or without abnormal SEP. However, patients with abnormal SEP showed an FA decrease in the dorsal column cephalic to the lesion (0.56±0.06) (ie, at C1/2, compared with healthy subjects [0.66±0.02]), but the same decrease was not observed for those without a SEP abnormality (0.67±0.02).ConclusionSpinal tracts were not uniformly affected in the myelopathic cervical cord. Changes in diffusion indices could delineate focal or extensive myelopathic lesions in CSM, which could account for abnormal SEP. DTI analysis of spinal tracts might provide additional information not available from conventional diagnostic tools for prognosis of CSM.     

Tracking of Environmental Determinants of Bone Structure and Strength Development in Healthy Boys: An Eight‐Year Follow Up Study on the Positive Interaction Between Physical Activity and Protein Intake From Prepuberty to Mid‐Late Adolescence

High protein (> median:Hprot) vs. moderate (< median:MProt) intake was shown to enhance the positive impact of high physical activity (HPA) on proximal femur BMC/aBMD/Area in healthy prepubertal boys. We tested the hypothesis that this synergistic effect would track and influence bone structure and strength until mid‐adolescence. BMC/aBMD/Area was measured at femoral neck (FN) and total hip (TotHip) by DXA in 176 boys at 7.4 ± 0.4 and 15.2 ± 0.5 years (± SD). Distal tibia (DistTib) microstructure and strength were also assessed at 15.2 years by high‐resolution peripheral computerized tomography (HR‐pQCT) and micro‐finite element analysis (µFEA). The positive impact of HProt vs. MProt on FN and TotHip BMC/aBMD/Area, recorded at 7.4 years remained unabated at 15.2 years. At this age, at DistTib, HProt‐HPA vs. MProt‐HPA was associated (p < 0.001) with larger cross‐sectional area (CSA, mm²), trabecular number (Tb.N, mm^?1) and lower trabecular separation (Tb.Sp, µm). The interaction between physical activity and protein intake was significant for CSA (p = 0.012) and Tb.N (p = 0.043). Under MProt (38.0 ± 6.9 g.d^?1), a difference in PA from 168 ± 40 to 303 ± 54 kcal.d^?1 was associated with greater stiffness (kN/mm) and failure load (N) of +0.16 and +0.14 Z‐score, respectively. In contrast, under HProt (56.2 ± 9.5 g.d^?1), a difference in PA of similar magnitude, from 167 ± 33 to 324 ± 80 kcal.d^?1, was associated with a larger difference in stiffness and failure load of +0.50 and +0.57 Z‐score, respectively. In conclusion, the positive influence of relatively HProt on the impact of HPA on proximal femur macrostructure tracks from prepuberty to mid‐late puberty. At this stage, the impact of HProt on HPA is also associated with microstructural changes that should confer greater mechanical resistance to weight‐bearing bones. These results underscore the importance of protein intake and exercise synergistic interaction in the early prevention of adult osteoporosis. © 2014 American Society for Bone and Mineral Research.     

Hydration and N-acetyl-l-cysteine alter the microstructure of human nail and bovine hoof: Implications for drug delivery

This work aimed to (a) characterize the microstructure and porosity of human nail and bovine hoof by mercury intrusion porosimetry and SEM image analysis, (b) study the effects of hydration and of N-acetyl-l-cysteine treatment on the microstructure of both membranes, and (c) determine whether the microstructural modifications were associated with changes in drug penetration measured by standard diffusion studies. Bovine hoof surface is more porous than nail surface although there were no differences between the mean surface pore sizes. Hydration and N-acetyl-l-cysteine increased the roughness and apparent surface porosity, and the porosity determined by mercury intrusion porosimetry of both membranes. Pore-Cor^TM was used to generate tridimensional structures having percolation characteristics comparable to nail and hooves. The modeled structures were horizontally banded having an inner less-porous area which disappeared upon treatment. Treatment increased the predicted permeability of the simulated structures. Triamcinolone permeation increased significantly for hooves treated N-acetyl-l-cysteine, i.e., the membranes for which microstructural and permeability changes were the largest. Thus, microstructural changes determined via mercury intrusion porosimetry and subsequently modeled by Pore-Cor^TM were related to drug diffusion. Further refinement of the technique will allow fast screening of penetration enhancers to be used in ungual drug delivery.     

Tradeoffs amongst fatigue, wear, and oxidation resistance of cross-linked ultra-high molecular weight polyethylene

This study evaluated the tradeoffs amongst fatigue crack propagation resistance, wear resistance, and oxidative stability in a wide variety of clinically-relevant cross-linked ultra-high molecular weight polyethylene. Highly cross-linked re-melted materials showed good oxidation and wear performance, but diminished fatigue crack propagation resistance. Highly cross-linked annealed materials showed good wear and fatigue performance, but poor oxidation resistance. Moderately cross-linked re-melted materials showed good oxidation resistance, but moderate wear and fatigue resistance. Increasing radiation dose increased wear resistance but decreased fatigue crack propagation resistance. Annealing reduced fatigue resistance less than re-melting, but left materials susceptible to oxidation. This appears to occur because annealing below the melting temperature after cross-linking increased the volume fraction and size of lamellae, but failed to neutralize all free radicals. Alternately, re-melting after cross-linking appeared to eliminate free radicals, but, restricted by the network of cross-links, the re-formed lamellae were fewer and smaller in size which resulted in poor fatigue crack propagation resistance. This is the first study to simultaneously evaluate fatigue crack propagation, wear, oxidation, and microstructure in a wide variety of clinically-relevant ultra-high. The tradeoff we have shown in fatigue, wear, and oxidation performance is critical to the material’s long-term success in total joint replacements.     

The role of heat treatment on microstructure and mechanical properties of Ti-13Zr-13Nb alloy for biomedical load bearing applications

The suitability of heat treated Ti–13Zr–13Nb (TZN) alloy for biomedical load bearing applications has been investigated. Depending upon the heat treatment conditions, the microstructure of TZN alloy mainly consists of α, β or α” martensite phases. In general, for all the deformation and solution treatment temperatures the variation of the hardness and tensile strength with cooling rate is similar. The elastic modulus of TZN alloy decreases with an increase in cooling rate from the solution treatment temperature. Relatively fine α+β microstructure increases the hardness and tensile strength. The presence of martensite and/or retained β in the microstructure decreases the hardness and elastic modulus and increases the ductility substantially whereas higher amount of α phase in the matrix increases the elastic modulus. Decomposition of martensite and retained β into α phase during aging increases the hardness, elastic modulus and tensile strength and decreases the ductility. Among the samples studied, the aged TZN sample, which was deformed and solution treated at 800 °C followed by water quenching, is a promising candidate for the application as implant material.     

骨碎补治疗去卵巢大鼠骨质疏松的实验研究

目的：观察骨碎补对去卵巢后骨质疏松大鼠骨密度、微结构和生物力学性能的影响,研究骨碎补对治疗骨质疏松的作用。方法：30只6月龄SD大鼠随机分为3组：去卵巢组（OVX）、假手术组（SHAM）和骨碎补治疗组（OVX＋D）。骨碎补治疗3个月后,检测各组大鼠的骨密度、微结构、生物力学性能的变化,并比较各组间差异。结果：OVX＋D组的的骨密度、微结构、生物力学指标与OVX组比较差异有统计学意义,与SHAM组比较差异无统计学意义。结论：骨碎补可以增加去卵巢后骨质疏松大鼠的骨密度,改善微结构,提高生物力学性能,对实验动物的骨质疏松有治疗作用。     

胰岛素样生长因子-I对尿道括约肌损伤修复影响的组织形态学研究

目的研究雌性大鼠尿道括约肌损伤后显微形态结构改变,探讨胰岛素样生长因子 I（insulin like growth factors I,IGF I）局部注射对其损伤后修复的影响。方法采用阴道扩张模拟产伤,建立大鼠尿道括约肌损伤模型,实验组大鼠(n=20)模型建立后尿道中段注射IGF I 1.0 μg（浓度0.1 μg&#8226;μL 1）,0.9%氯化钠溶液对照组(n=20)模型建立后中段尿道注射无菌0.9%氯化钠溶液10 μL,正常对照组(n=4)既无损伤也不做任何处理。取正常对照组中段尿道,并于损伤后2,4,6,8,14 d取治疗组和0.9%氯化钠溶液对照组大鼠中段尿道,行Masson’s trichrome染色,观察其显微结构动态改变,并定量分析尿道横纹肌、平滑肌及结缔组织组成。结果大鼠尿道括约肌损伤后中段尿道横纹肌、平滑肌出现断裂、萎缩、结构紊乱,胶原结缔组织增生明显。实验组与0.9%氯化钠溶液对照组比较,8,14 d肌组织所占尿道横截面积比例明显增高（P＜0.05）,肌纤维增生丰富,形态结构更完整。结论局部注射外源性IGF I能促进尿道括约肌肌细胞损伤后的修复,IGF I对尿道括约肌损伤具有潜在的治疗作用。