No abstract

Determination of the strength of rocks is very troublesome since it takes much time and effort to produce good test pieces. Therefore some methods for rapid determination of the strength of rocks are strongly demanded. The authors have investigated how to determine the strength of rock with irregular test pieces, i. e. rock pieces which are not machined. By theoretical as well as experimental study, they have obtained such a method to determine rapidly the tensile strength of rocks that an irregular test piece is crushed into two pieces by a concentrated load F, the distance between the points of loading being 2a, and then the tensile strength of the rock is given by 1.4 F,2002

No abstract

There are several reports that a protein-free extract of heart muscles from mamma lian animals dilates coronary vessels (1, 2), increases the amplitude of heart (3), and im proves the efficiency of contractions in heart lung preparations (4). Clinically, the extract has been used as an antianginal drug (5, 6), and a drug for heart failure contradictorily (7,8). One of the main approaches to antianginal drugs has been studies of coronary dilators. However, the majority of pharmacological studies have been carried out in animals with a normal coronary circulation and the results obtained may not predict the status of the abnormal coronary circulation. Certainly, studies in man indicate that the coronary bed of the anginal patient is incapable of dilatation so that nitroglycerin produces no increase in coronary flow (9, 10). Furthermore, some reports show that dipyridamol having specific potent coronary vasodilating activity is not effective for angina pectoris (11-13). Thus, many other approaches have been tried to investigate antiangi nal drugs. Clinically, ST segment depression in electrocadiogram of patients of angina pectoris is very common phenomenon, and we consider ST segment depression in rats produced with vasopressin or adrenaline might be one of the experimental models of an gina pectoris. Lindner et al. have shown that the vasopressin induced ischemia of the dog heart was improved after three daily injections of the large doses of a heart extract (14). Black have shown that oral administration of a heart extract for two weeks pro duced improvement on the above mentioned ischemia in rabbits (15). This paper des cribes a modification of similar experimental methods in rats and the identification of components which improves the ST segment depression in the heart extract. MATERIALS AND METHODS Animal experimentsElectrocardiogram (ECG) was recorded with male rats of Donryu strain weighing 170 to 220 g, anesthetized with intra-peritoneal administration of sodium pentobarbital (60 mg/kg). Conscious rats and male rabbits, being conscious or anesthetized with sodium pentobarbital, were used in the preliminary experiment. Myocardial hypoxia was pro

Our original phantom models the relationships among the blood perfusion, water diffusion, and biomechanics of the intracranial tissue, potentially facilitating the validation of novel MRI techniques and optimization of imaging parameters.