Summary: The morphology of the transcrystalline layer grown by nucleating high density polyethylene on fibers of ultra high molecular weight polyethylene was investigated by microbeam synchrotron X‐ray diffraction. Scanning with a 2 micron step size, it was possible to determine that near the fiber surface, the polymer chains of the transcrystalline layer are oriented at an angle of approx. 41° with respect to the fiber axis. This is consistent with the lamellar fold surface (the {201} plane) being close to perpendicular to the fiber axis. The X‐ray data support gradual twisting of the lamellae about the growth direction (the orthorhombic crystallite b‐axis) at a rate of ~0.85° per micron of radial distance from the fiber surface.
Polarized light micrograph of the transcrystalline layer in a PE/PE composite. The width of the fiber is approximately 20 μm. 相似文献
The effects of ageing on the numbers of alveolar pores of Kohn and on the cytoplasmic components of alveolar type II cells were studied in monkey lungs by scanning and transmission electron microscopy. Lung tissue from 26 female and three male pigtail macaques whose ages ranged from 1 month to 31 years (life span is 35 years) was analysed. From the age of 1 month to 10 years there was a significant increase in the number of alveolar pores (r = 0.85, p less than 0. 001); however, between the ages of 14 years to 31 years there was no significant change. In seven animals ranging in age from 1 month to 4 years (mean 2.4 years) the number of pores was 5.8 +/- 3.9 (mean +/- S.D.), whereas in 10 animals aged 16 to 31 years (mean 20.3 years) the number of pores was 32.7 +/- 17.5 (mean +/- S.D.) per alveolar profile, a significant difference (p less than 0.002). In older animals (15-20 years) there was a significant decrease, both in the number of lamellar bodies per alveolar type II cell (p less than 0.01) and in the volume density of lamellar bodies to cytoplasmic volume (p less than 0.05) compared with young animals (1 month to 4.8 years). In older animals, there was also a significant increase in the volume density of a vacuole-like dilatation of the endoplasmic reticulum in alveolar type II cells (p less than 0.05) compared with young animals. These findings suggest impaired pulmonary surfactant production with aging. Both the increased number of alveolar pores and the postulated decrease of surfactant production could play a role in the pathogenesis of pulmonary emphysema. 相似文献
AIMS: To describe a new surgical technique for deep stromal anterior lamellar keratoplasty. METHODS: In eye bank eyes and sighted human eyes, aqueous was exchanged by air, to visualise the posterior corneal surface--that is, the "air to endothelium" interface. Through a 5.0 mm scleral incision, a deep stromal pocket was created across the cornea, using the air to endothelium interface as a reference plane for dissection depth. The pocket was filled with viscoelastic, and an anterior corneal lamella was excised. A full thickness donor button was sutured into the recipient bed after stripping its Descemet's membrane. RESULTS: In 25 consecutive human eye bank eyes, a 12% microperforation rate was found. Corneal dissection depth averaged 95.4% (SD 2.7%). Six patient eyes had uneventful surgeries; in a seventh eye, perforation of the lamellar bed occurred. All transplants cleared. Central pachymetry ranged from 0.62 to 0.73 mm. CONCLUSION: With this technique a deep stromal anterior lamellar keratoplasty can be performed with the donor to recipient interface just anterior to the posterior corneal surface. The technique has the advantage that the dissection can be completed in the event of inadvertent microperforation, or that the procedure can be aborted to perform a planned penetrating keratoplasty. 相似文献
To evaluate the maneuverability and efficacy of phacoemulsification and intraocular lens (IOL) implantation in eyes with corneal opacities after deep anterior lamellar keratoplasty (DALK), twelve eyes of 12 patients with mild to moderate corneal opacities after DALK and coexisting cataracts were analyzed retrospectively. Phacoemulsification and IOL implantation assisted with anterior capsule staining, as well as non-invasive optical fiber illumination, were performed on all eyes. No intraoperative or postoperative complications were noted. Mean corrected distance visual acuity (logMAR) improved from 1.24±0.17 to 0.73±0.22. Post-phaco intraocular pressure was maintained between 13 to 20 mm Hg in all cases throughout the follow-up period. Mean endothelial cell density decreased from 2258.42±205.94 to 1906.25±174.23 cells/mm2. Phacoemulsification and IOL implantation are safe and valid in eyes with mild to moderate corneal opacities after DALK and coexisting cataracts when assisted with anterior capsule staining and non-invasive optical fiber illumination. 相似文献
Birds in the genus Pitohui and Ifrita carry potent neurotoxins that are most abundant in skin and feathers. It was unknown precisely how or where in the skin these chemicals are stored. Here, we report high‐resolution electron microscopy using OsO4 staining to visualize the location of alkaloids. Our images suggest that toxic alkaloids accumulate in multigranular bodies of epidermal cells and are likely secreted as part of the avian epidermal barrier, where they are made available for chemical defense. 相似文献