Nucleation process in the Burridge-Knopoff model of earthquakes

Nucleation process of the one-dimensional Burridge-Knopoff model of earthquakes obeying the rate- and state-dependent friction law is studied both analytically and numerically. The properties of the nucleation dynamics, the nucleation lengths and the duration times are examined together with their continuum limits.Comment: Title changed, one figure (previous Fig.2) omitted, several references (new Refs.5-8,21,24-28) added, and two eqs. (new eqs.1,5) added. Text expanded considerably, especially the part explaining the relation of the model to the elastic continuum model. To appear in Europhys. Letter

Tortuosity of the brachiocephalic artery complicated with arterial injury after tracheotomy: a case report

Tracheotomy is an operation of the airway performed even on critical care patients. Surgical complications of tracheotomies are fatal. In this study, tortuosity of the brachiocephalic artery complicated with arterial injury was observed in a patient after tracheotomy. A 95-year-old woman in coma was admitted to our medical center. The patient needed airway management, and tracheal intubation was performed. The cause of the coma was extensive cerebral infarction of the right middle cerebral artery. It was expected that the coma would be prolonged, and a tracheotomy was performed after 7 days. Tortuosity of the brachiocephalic artery was confirmed with cervical computed tomography before surgery. The patient bled through the tracheostomy after 30 days. To arrest bleeding from the right common carotid artery, a vascular repair surgery was performed. There was no recurrent bleeding after surgery. After 37 days, the patient died of deteriorating primary disease. Although tracheotomy is a common operation, attention should be paid to abnormalities of blood vessels including tortuosity of the brachiocephalic artery

Dynamics of earthquake nucleation process represented by the Burridge-Knopoff model

Dynamics of earthquake nucleation process is studied on the basis of the one-dimensional Burridge-Knopoff (BK) model obeying the rate- and state-dependent friction (RSF) law. We investigate the properties of the model at each stage of the nucleation process, including the quasi-static initial phase, the unstable acceleration phase and the high-speed rupture phase or a mainshock. Two kinds of nucleation lengths L_sc and L_c are identified and investigated. The nucleation length L_sc and the initial phase exist only for a weak frictional instability regime, while the nucleation length L_c and the acceleration phase exist for both weak and strong instability regimes. Both L_sc and L_c are found to be determined by the model parameters, the frictional weakening parameter and the elastic stiffness parameter, hardly dependent on the size of an ensuing mainshock. The sliding velocity is extremely slow in the initial phase up to L_sc, of order the pulling speed of the plate, while it reaches a detectable level at a certain stage of the acceleration phase. The continuum limits of the results are discussed. The continuum limit of the BK model lies in the weak frictional instability regime so that a mature homogeneous fault under the RSF law always accompanies the quasi-static nucleation process. Duration times of each stage of the nucleation process are examined. The relation to the elastic continuum model and implications to real seismicity are discussed.Comment: Title changed. Changes mainly in abstract and in section 1. To appear in European Physical Journal

Research Activities in the Department of Physical Therapy

[Introduction] It is already fifty years since the Japanese law of physical therapists and occupational therapists has been effective. The physical therapist is referred by the law as "the professionals who implements the physical therapy to persons with disabilities under the prescription of medical doctors". In fifty years, however, the target of physical therapy has been significantly expanded. The subject for physical therapy now includes the patients in acute disease just after the surgical operation in addition to those in rehabilitation stage. In other words, the physical therapy is now recognized as the indispensable intervention to the subject with acute as well as chronic disorders. On the other hand, due to a rapid transition of the society into the aged society, prevention of diseases, and decline of activity capacity due to the aging have become major issues for the physical therapy

Direct and Efficient Production of Ethanol from Cellulosic Material with a Yeast Strain Displaying Cellulolytic Enzymes

For direct and efficient ethanol production from cellulosic materials, we constructed a novel cellulose-degrading yeast strain by genetically codisplaying two cellulolytic enzymes on the cell surface of Saccharomyces cerevisiae. By using a cell surface engineering system based on α-agglutinin, endoglucanase II (EGII) from the filamentous fungus Trichoderma reesei QM9414 was displayed on the cell surface as a fusion protein containing an RGSHis6 (Arg-Gly-Ser-His(6)) peptide tag in the N-terminal region. EGII activity was detected in the cell pellet fraction but not in the culture supernatant. Localization of the RGSHis6-EGII-α-agglutinin fusion protein on the cell surface was confirmed by immunofluorescence microscopy. The yeast strain displaying EGII showed significantly elevated hydrolytic activity toward barley β-glucan, a linear polysaccharide composed of an average of 1,200 glucose residues. In a further step, EGII and β-glucosidase 1 from Aspergillus aculeatus No. F-50 were codisplayed on the cell surface. The resulting yeast cells could grow in synthetic medium containing β-glucan as the sole carbon source and could directly ferment 45 g of β-glucan per liter to produce 16.5 g of ethanol per liter within about 50 h. The yield in terms of grams of ethanol produced per gram of carbohydrate utilized was 0.48 g/g, which corresponds to 93.3% of the theoretical yield. This result indicates that efficient simultaneous saccharification and fermentation of cellulose to ethanol are carried out by a recombinant yeast cells displaying cellulolytic enzymes