A Mixed Optimal Control Approach for Upstream Fish Migration

This paper proposes a simple mathematical model forupstream fish migration along rivers. The model describes the fish migration along a river based on a mixed optimal control approach having swimming velocity, school size, and stopping time of migration as control variables. The optimization problem reduces to a variational inequality. Its explicit “viscosity” solution is presented with the dependence of the fish migration on river environment. To prove uniqueness of the solution to the variational inequality requires a constructive argument not based on the conventional theorems. A novel finite difference scheme for solving the variational inequality is also proposed with its convergence results. An application example of the model discusses the upstream migration of Plecoglossus altivelis (Ayu) in Japan, which evaluates the dependence of the fish migration on the habitat quality and provides recommendations for managing river environment. This is an interdisciplinary research between environmental and mathematical fields

Electrical Spin Injection into Silicon using MgO Tunnel Barrier

We observed spin injection into silicon through Fe/MgO tunnel barrier by using non-local magnetoresistance measurement technique. Fe/MgO tunnel barrier contacts with a lateral spin valve structure were fabricated on phosphorous doped silicon-on-insulator substrate. Spin injection signals in the non-local scheme were observed up to 120K, which is the highest value where band transferred spins in Si have ever been reported, and spin diffusion length was estimated to be about 2.25um at 8K. Temperature dependence and injection current dependence of the non-local voltage were also investigated. It is clarified that MgO tunnel barrier is effective for the spin injection into silicon.Comment: 15pages, 4 figures. To appear in Applied Physics Expres

A role for fungal β-glucans and their receptor Dectin-1 in the induction of autoimmune arthritis in genetically susceptible mice

A combination of genetic and environmental factors can cause autoimmune disease in animals. SKG mice, which are genetically prone to develop autoimmune arthritis, fail to develop the disease under a microbially clean condition, despite active thymic production of arthritogenic autoimmune T cells and their persistence in the periphery. However, in the clean environment, a single intraperitoneal injection of zymosan, a crude fungal β-glucan, or purified β-glucans such as curdlan and laminarin can trigger severe chronic arthritis in SKG mice, but only transient arthritis in normal mice. Blockade of Dectin-1, a major β-glucan receptor, can prevent SKG arthritis triggered by β-glucans, which strongly activate dendritic cells in vitro in a Dectin-1–dependent but Toll-like receptor-independent manner. Furthermore, antibiotic treatment against fungi can prevent SKG arthritis in an arthritis-prone microbial environment. Multiple injections of polyinosinic-polycytidylic acid double-stranded RNA also elicit mild arthritis in SKG mice. Thus, specific microbes, including fungi and viruses, may evoke autoimmune arthritis such as rheumatoid arthritis by stimulating innate immunity in individuals who harbor potentially arthritogenic autoimmune T cells as a result of genetic anomalies or variations

Molecular Interactions of Surface Protein Peptides of Streptococcus gordonii with Human Salivary Components

Oral streptococci play a large role in dental biofilm formation, and several types interact as early colonizers with the enamel salivary pellicle to form the primary biofilm, as well as to incorporate other bacteria on tooth surfaces. Interactions of surface molecules of individual streptococci with the salivary pellicle on the tooth surface have an influence on the etiological properties of an oral biofilm. To elucidate the molecular interactions of streptococci with salivary components, binding between surface protein (SspB and PAg) peptides of Streptococcus gordonii and Streptococcus sobrinus were investigated by utilizing BIAcore biosensor technology. The analogous peptide [change of T at position 400 to K in SspB(390-402), resulting in the SspB(390-T400K-402) peptide] from S. gordonii showed the greatest response for binding to salivary components and inhibited the binding of Streptococcus sanguis by more than 50% in a competitive inhibition assay in a comparison with other SspB and PAg peptides. This peptide also bound to the high-molecular-weight protein complex of salivary components and the agglutinin (gp340/DMBT1) peptide (scavenger receptor cysteine-rich domain peptide 2 [SRCRP 2]). In addition, the SspB(390-T400K-402) peptide was visualized by two surface positive charges in connection with the positively charged residues, in which lysine was a key residue for binding. Therefore, the region containing lysine may have binding activity in S. gordonii and S. sanguis, and the SRCRP 2 region may function as a receptor for the binding. These findings may provide useful information regarding the molecular mechanism of early biofilm formation by streptococci on tooth surfaces

胸壁外に設置した拍動型補助人工心臓に関する前臨床的研究

An assistance artificial heart was fabricated with blood compatible polyurethane　having 3 different sizes and was evaluated by a series of preclinical experiment in　calves. The following results were obtained. 1) The artificial heart was constructed in 3 sizes of 60, 80 and 100 cc in capacity　and is activated by a pneumatic heart driver console. 2) The mock circulation revealed that this assistance heart has ejection fraction of　80-95%. 3) Safe use of assistance heart has been confirmed by implantation in 18 calves　with intact or failured hearts over a period of 3 months. 4) Weaning could be performed in cases where myocardial necrosis of the left　ventricle is induced less than 35% utilizing myocardial injection of 5N-NaOH. However　pump dependency develops for a necrosis exceeding 35 %. 5) Thus we concluded that this system can be safely employed for a one month　cardiac assistance clinically and at most for a 3 months support in pump dependent　cases. 6) The technique was developed to make the instant shift possible within a few　minutes from the conventional non-pulsatile bypass assistance to the assistance heart