Decreasing the number of test specimens by utilizing both fracture stress and fracture location for the estimation of Weibull parameter

In a bending load test for brittle materials, such as ceramics for spacecraft and aircraft, decreasing the number of test specimens required is a crucial problem. This paper discusses the effectiveness of using the information of both fracture stress and fracture location to decrease the number of specimens required to obtain the same precision as the Weibull estimator. The following results were obtained: It was found that by adding the fracture location information, the precision of the Weibull parameter estimation under the optimal design became 1.5–1.9 times better compared with the case of using only the fracture stresses. This means the number of samples necessary to attain the same precision becomes 1/1.5–1/1.9. Tables and figures which give information on the number of samples necessary to attain the required precision are given.     

Evaluation by microneurography of muscle sympathetic nerve activity in myelopathic patients

The purpose of this study was to observe the functional condition of the muscle sympathetic nerve activity (MSNA) in nine patients with mild myelopathy for which surgery was indicated [mean score 14/17 by Japanese Orthopaedic Association (JOA) cervical myelopathy and 7/11 for thoracic myelopathy]. The MSNA was obtained from the tibial nerve at the popliteal fossa by microneurography. The resting activities and the responses during handgripping were analyzed and compared with those of a control group of nine healthy volunteers and patients with disorders unrelated to myelopathy. The MSNA with the subjects supine was recorded first at rest for 5 min. (rest period), next during exertion of 20% of the maximum voluntary handgripping power for 5 min. (handgripping period), and last at rest for 5 min. (recovery period). The number of MSNA bursts per min. (burst rate) in the group with myelopathy was more than that in the control group (p < 0.05) in all three periods. The response by MSNA to handgripping in the group with myelopathy was higher than that in the control group at the start of handgripping (p < 0.01), and tended to be higher even 5 min. after handgripping ended. The results appeared to demonstrate that MSNA of patients with mild myelopathy for which surgery is indicated is increased in the lower extremities.     

Surgical treatment of ventricular tachycardia after surgical repair of tetralogy of Fallot. Relation between intraoperative mapping and histological findings

BACKGROUND: The mechanism of ventricular tachycardia (VT) after correction of tetralogy of Fallot (TF) is poorly understood. The purpose of this study was to examine the histopathology of the arrhythmogenic area detected by intraoperative mapping. METHODS AND RESULTS: The patients were three men who underwent radical surgery for TF at age 3, 3, or 5 years, respectively. VT developed at 8, 9, or 11 years, respectively, after surgery, and shock developed during VT in every case. The ECG revealed monomorphic VT in two cases and polymorphic VT in one case. Induction of VT resulted in a wide left-axis deviation-pattern QRS with cycle lengths varying between 260 and 330 milliseconds. The VT origin was identified at the right ventricular outflow tract (RVOT). A radical operation was performed with the patient under cardiopulmonary bypass. On epicardial mapping, delayed activation of the RVOT was recorded during sinus rhythm, and clockwise circus movement of the macroreentry current during VT on the right ventricular free wall was documented in each case. The VTs were treated successfully by surgical resection and cryoablation of the myocardium. In every patient, histology of the myocardial specimens showed degeneration, adiposis, fibrosis, inflammatory cell infiltration, and scattered myocyte islets. These lesions corresponded anatomically to the area of myocardium in which delayed activation was evident during epicardial mapping. CONCLUSIONS: The results of this study indicate that patients with VT after radical correction of the TF have abnormal histopathological findings at the site of the prior right ventriculotomy scar. These lesions were noted within the region of delayed activation found during epicardial mapping and were found to be a part of the reentrant circuit.     

Properties of networks obtained by internal plasticization of epoxy resin with aromatic and aliphatic glycidyl compounds

In order to improve the fracture properties of p, p′-diaminodiphenylmethane-cured epoxy resin, various kinds of aromatic and aliphatic glycidyl compounds were investigated as a modifier at an amount of 30 wt %. Several compounds promoted the fracture toughness. In any glycidyl compounds, however, heat resistance was decreased by the modification. The dynamic mechanical properties of the modified epoxy resins were measured. The crosslinking density ρ was calculated from the theory of rubber elasticity, and the mechanical properties of the resins were discussed in regard to the crosslinking density. Tensile strength was scarcely affected by the crosslinking density. Elongation at break and Izod impact strength increased remarkably with decrease in crosslinking density. The fracture toughness K_Ic- increased with decrease in crosslinking density except at small ρ.     

Tricuspid annuloplasty with Carpentier''s prosthetic ring in tricuspid insufficiency combined with mitral valve insufficiency

A case of bilateral hypernephroma treated by right heminephrectomy in situ and "benchwork" excision of two tumors from the left kidney followed by autotransplantation is presented. Follow-up examination has demonstrated good renal function with no evidence of tumor recurrence or metastasis. This case illustrates the feasibility of benchwork operation and its application to renal tumors, particularly when these tumors are bilateral and preservation of renal tissue is imperative. Long-term follow-up of patients managed by this technique is mandatory.     

Note: high-pressure generation using nano-polycrystalline diamonds as anvil materials

Nano-polycrystalline diamonds (NPDs) consist of nanosized diamond grains oriented in random directions. They have high toughness and isotropic mechanical properties. A NPD has neither the cleavage feature nor the anisotropy of hardness peculiar to single-crystal diamonds. Therefore, it is thought to be useful as a diamond anvil. We previously reported the usefulness of a NPD as an anvil for high-pressure development. In this study, some additional high-pressure generating tests using diamond anvils of various shapes prepared from NPDs were conducted to investigate the advantage of using NPDs for anvil applications. The results revealed that the achievable pressure value of a NPD anvil with a culet size of more than 300 μm is about 1.5 to 2 times higher than that of single-crystal diamond anvils, indicating that NPD anvils have considerable potential for large-volume diamond anvils with large culet sizes.