Bulk porosity, along with size and spatial distribution of pores, play key roles in strength of porous ceramics, as reported in a study on porous alumina. Hence, a fracture mechanics procedure was proposed to evaluate their strength by presuming that behavior of pore distribution is equivalent to that of crack distribution, and each pore is surrounded by virtual crack. In contrast to alumina, zirconia has distinct spherical‐shaped pores. Moreover, its strength properties vary with stabilizing additives. In this research, strength properties of yttria‐stabilized zirconia ceramics were studied to verify applicability of the procedure proposed for simulating strength of porous ceramics. The effect of pore characteristics on static strength properties was determined experimentally and confirmed by Monte‐Carlo simulations. It was revealed that simulated strength coincided with experimental results within a narrow scatter band, ie, factor of 21/2. Therefore, the proposed procedure was found to be appropriate for estimating strength of porous zirconia.
Background Malignant hyperthermia (MH) is a rare genetic disease characterized by the development of very serious symptoms, and hence prompt and appropriate treatment is required. However, postoperative MH is very rare, representing only 1.9% of cases as reported in the North American Malignant Hyperthermia Registry (NAMHR). We report a rare case of a patient who developed sudden postoperative hyperthermia after mastectomy, which was definitively diagnosed as MH by the calcium-induced calcium release rate (CICR) measurement test. Case presentation A 61-year-old Japanese woman with a history of stroke was hospitalized for breast cancer surgery. General anesthesia was introduced by propofol, remifentanil, and rocuronium. After intubation, anesthesia was maintained using propofol and remifentanil, and mastectomy and muscle flap reconstruction surgery was performed and completed without any major problems. After confirming her spontaneous breathing, sugammadex was administered and she was extubated. Thereafter, systemic shivering and masseter spasm appeared, and a rapid increase in body temperature (maximum: 38.9 °C) and end-tidal carbon dioxide (ETCO2) (maximum: 59 mmHg) was noted. We suspected MH and started cooling the body surface of the axilla, cervix, and body trunk, and administered chilled potassium-free fluid and dantrolene. After her body temperature dropped and her shivering improved, dantrolene administration was ended, and finally she was taken to the intensive care unit (ICU). Body cooling was continued within the target range of 36–37 °C in the ICU. No consciousness disorder, hypotension, increased serum potassium level, metabolic acidosis, or cola-colored urine was observed during her ICU stay. Subsequently, her general condition improved and she was discharged on day 12. Muscle biopsy after discharge was performed and provided a definitive diagnosis of MH. Conclusions The occurrence of MH can be life-threatening, but its frequency is very low, and genetic testing and muscle biopsy are required to confirm the diagnosis. On retrospective evaluation using the malignant hyperthermia scale, the present case was almost certainly that of a patient with MH. Prompt recognition and immediate treatment with dantrolene administration and body cooling effectively reversed a potentially fatal syndrome. This was hence a valuable case of a patient with postoperative MH that led to a confirmed diagnosis by CICR.
It is well known that porous ceramics have higher heat-resistance and larger specific surface area. So, porous ceramics are suitable for applications to functional components such as refractory, filters and catalysts. Even if applications of porous ceramics are functional, their strength properties should be adequately evaluated to guarantee long-term durability with satisfying the required functions. In previous studies (Yoshida et al., 2006) (Fujii et al., 2007), strength properties of porous ceramics were discussed by considering bulk porosity only. It has been recognized that the strength of porous ceramics with higher bulk porosity becomes lower in general. It should be noted, however, that not only bulk porosity but also spatial and size distributions of pores affect strength properties of porous ceramics; e.g., there is possibility that the strength of a porous ceramic material with higher bulk porosity increases by decreasing sizes of individual pores within the material. Actually, such an irregular behavior was confirmed in a porous alumina (Miyazaki and Hoshide, 2018). From a viewpoint of material design, it is desired that the strength properties can be predicted for pore characteristics resulted from a specified processing of porous ceramics. The strength properties are usually obtained by experiments. However, if the strength properties are determined experimentally, various ceramic materials with different porosities should be produced and a lot of specimens for respective materials should be prepared because very large scatter of strength is well-known in ceramics. Consequently, it is convenient that virtual porous ceramics with various porosities can be made and strength
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