Toru Kuriyama

Candida biofilms and oral candidosis: treatment and prevention

In recent years, there has been a significant increase in the incidence of human fungal infections (60). A number of factors have been implicated with this increase, but it is generally accepted that the main influences relate to the more widespread provision of new medical practices, such as immunosuppressive therapy and use of broad spectrum antibiotics, and invasive surgical procedures such as solid organ or bone marrow transplantation. Infections may either be superficial, affecting the skin, hair, nails and mucosal membranes, or systemic, involving major body organs (95). The risk of systemic infection appears to be enhanced in cases where the individual is already colonized by Candida (71). With regard to superficial mucosal infections, the continued spread of HIV infection (29) and the more extensive use of inhaled steroids (36) have also played significant roles. Of the fungi regarded as human pathogens, members of the genus Candida are amongst the most frequently recovered from disease. The Candida genus is a taxomomic grouping that was originally used to define yeast-like organisms that were not considered to have a sexual reproductive life cycle. Candida contains over 350 heterogeneous species, but only a minority of these have been implicated in human disease (Table 1). Infections caused by Candida are collectively referred to in the plural as candidoses (singular candidosis) or candidiases (singular candidiasis). Both terms are used in the literature although candidosis is preferred to candidiasis by many due to the -osis part of the word being consistent with the nomenclature used for other fungal infections. Of the Candida species isolated from humans, Candida albicans is the most prevalent in both health and disease. It is generally accepted that commensal carriage of this species occurs in approximately 50% of individuals (81, 107), although figures do vary depending on the population examined. Mycological studies have shown that C. albicans represents over 80% of isolates from all forms of human candidosis (85). However, the so-called non-Candida albicans Candida species are increasingly recognized as important agents of human infection (41, 46, 55, 72). The apparently increased involvement of non-Candida albicans Candida species in human candidoses may partly relate to improvements in diagnostic methods, such as the use of primary agars with the ability to differentiate species, and the introduction of molecular techniques in the routine diagnosis of fungaemia (64). However, the increased prevalence of non-Candida albicans Candida species in disease could also be a reflection of the inherently higher level of antifungal drug resistance in some nonCandida albicans Candida species (39) compared with C. albicans, as this would promote their persistence, possibly to the detriment of C. albicans, in mixed-species infections treated with traditional antifungal agents. Candidoses have been recognized throughout human history and are often described as being diseases of the diseased , reflecting the opportunistic pathogenic nature of Candida. Whilst Candida species are generally regarded as harmless members of the healthy commensal microflora of humans, infection can arise if a colonized individual becomes immunocompromised. Candida species have been encountered in a wide spectrum of diseases, and almost all human body organs can become infected (79). Systemic infections are rare, but are serious when they do occur, with

Design and test results of 6.6 kV high-Tc superconducting fault current limiter

A 6.6 kV single-phase fault current limiter (FCL) using a high-Tc superconducting coil as a limiting coil was developed. The development is a preliminary step to investigate the feasibility of the FCL application for high-voltage transmission lines. The FCL is of the rectifier type and is mainly comprised of a limiting coil, a sub-cooled nitrogen cryostat with a cryocooler, and a rectifier bridge. The limiting coil, wound as a solenoid by Ag/Mn sheathed Bi-2223 tapes, has an inductance of 30 mH. It is immersed in a liquid nitrogen bath in the cryostat. A Gifford-McMahon cryocooler cools the cryogen below 77.3 K. A pressure regulator keeps the cryogen at an atmospheric pressure. The coil has a critical current of 70 A at 64 K and endures a 50 Hz overvoltage of 22 kV against the ground. In a fault current limiting test with a short-circuit generator, a short-circuit current of 12.5 kA was limited to 1.2 kA.

Development of magnetic refrigerator for room temperature application

This paper describes experimental results of a magnetic refrigerator operated at room temperature. Spheres of Gadolinium, 2.2 kg in weight and 0.3 mm in diameter, are used as a magnetic working material. The magnetic materials were divided into two vessels and reciprocated between high and zero magnetic fields. High magnetic field up to 4 T was applied by a cryocooler cooled superconducting magnet. Refrigeration capacity of 100 W was obtained with operating frequency of 0.167 Hz. Details of the magnetic refrigerator construction and experimental results are presented.

High Efficient two-Stage gm Refrigerator with Magnetic Material in the Liquid Helium Temperature Region

This paper describes experimental results obtained from a two-stage Gifford-McMahon (GM) refrigerator which uses a rare earth compound as a 2nd regenerator matrix instead of Pb (lead) matrix. The refrigeration capacity below 10 K for a conventional two-stage GM refrigerator is so small that the lowest temperature achieved is limited to the 8 K level. The purpose of this study is to improve the refrigeration performance in the temperature region below 10 K. The technical point is to use Er3Ni (Erbium-3 Nickel) as a 2nd stage regenerator matrix, because it has much larger volumetric specific heat than Pb below 15 K and has almost the same specific heat as Pb at higher temperature. The reciprocating speed was optimized to improve the refrigeration performance. Refrigeration capacity of 1 W at 6.59 K and no load temperature of 4.50 K were obtained from the Er3Ni regenerator. The refrigeration loss mechanism below 10 K is also discussed.

The Project Overview of the HTS Magnet for Superconducting Maglev

This paper describes the outline of a development project for the HTS magnet for the superconducting Maglev, which commenced in 1999. A very small current decay rate of 0.44%/day was achieved in 2003, using a prototype HTS coil, and a second HTS magnet, consisting of four persistent current HTS coils, was produced in 2005 for vehicle running tests. The second HTS magnet was operated in a persistent current mode at a rated magneto-motive force of 750 kA, and a top speed of 553 km/h was attained on the Yamanashi Maglev Test Line on December 2,2005.

Development of 66 kV/750 A High-T/sub c/ superconducting fault current limiter magnet

One of the items included in the Super-conductive AC Equipment (Super-ACE) project, being performed from 2000 to 2004, is a development of a 66 kV/750 A high-T/sub c/superconducting (HTS) fault current limiter (FCL) magnet. This research focuses on fundamental technical items essential for a 66 kV class fault current limiter, that is, high current capacity, high voltage insulation and sub-cooled nitrogen cooling. This paper describes the design of the magnet and the test results obtained so far. The magnet mainly consists of a vacuum vessel, a nitrogen bath, a pair of current leads, cryocoolers, and six sets of unit-coils wound with Bi2223 tapes. The rated current of each coil is about 125 A at 70 K, and so the total current capacity of the magnet is 750 A. The insulation voltage of the magnet is of the 66 kV class. By the end of FY2002, three sets of the unit coils were set connected in the cryostat and some evaluation tests were implemented as a milestone of the program. In the cooling down test, sub-cooled nitrogen of 65 K was obtained with homogenous temperature distribution in the cryogen. In the overvoltage test, no breakdowns were observed in the case of applying both ac voltage of 140 kV for one minute and lightning impulse voltage of 350 kV. Voltage-current characteristics of the coils were measured in sub-cooled nitrogen. The rated current of 375 A was successfully obtained for both direct and alternate current tests. All the targets constituting the milestone of the 66 kV/750 A magnet development were achieved.

Development of a 1 MJ cryocooler-cooled split magnet with Ag-sheathed Bi2223 tapes for Si single-crystal growth applications

A project to develop a high-temperature superconducting split magnet for Si single-crystal growth applications began in October 1997 and is scheduled to be completed for three years. The project is being executed on the basis of collaboration between Toshiba Corp., Sumitomo Electric Industries Ltd. and Shin-Etsu Handotai Co. Ltd., and is partially funded by Ministry of International Trade and Industry (MITI) of Japan. The purpose of this project is to confirm the energy-saving performance and high reliability of a large HTS split magnet (1 MJ) using Bi2223 tapes. This split coil system is composed of 2 coils, each consisting of 18 pancakes, and the total length of HTS tapes is approximately 80 km. The magnet is to be cooled to below 20 K by a highly efficient GM-type cryocooler in order to make overall current density of the magnet close to the density of metal superconducting magnets. In the first year of this project, a conceptual design was established and R&D of the fragile HTS tapes was carried out. In the second year, the design, fabrication, testing and evaluation of an experimental magnet, incorporating pancake coils of the same size as those of the actual magnet, has been accomplished. This work will contribute to the improvement of the design and fabrication of the full-scale magnet in the final year of this project.

Persistent current HTS magnet cooled by cryocooler (1)-project overview

This paper describes a project overview for a persistent current HTS magnet, which has been in development for Maglev trains since 1999. The HTS magnet operates with a very small current decay rate of 0.44%/day and can be cooled by a cryocooler below 20 K. The HTS coil consists of 12 single-pancake coils, which were wound with 4 parallel Ag-sheathed Bi2223 tapes. In order to minimize the magnetic field decay rate during persistent current operation, we have made efforts not to decrease the high Tc superconductor characteristics during the winding of the single-pancake coils. The HTS coil is connected with a persistent current switch made of a YBCO thin film, and cooled by a G-M (Gifford-MacMahon) type two-stage pulse tube cryocooler. Detachable current leads were used to reduce heat leakage to the 1st stage of the cryocooler.

Persistent current HTS magnet cooled by cryocooler (4) - persistent current switch characteristics

We developed a persistent current high temperature superconducting (HTS) magnet for Maglev train. The HTS magnet mainly consists of an HTS coil, a persistent current switch (PCS), a GM type two-stage pulse tube cryocooler. A PCS is one of the most important components to maintain persistent current operation. A YBCO thin film was adopted for a PCS conductor because it has a high resistivity over a critical temperature and a high critical current density at lower temperatures. Persistent current mode operation tests were successfully carried out with the PCS. The current decay rate at the rated current operation of 532 A was 0.44%/day which was investigated by measuring the magnetic field at the center of the coil.

HTS Magnet for Maglev Applications (1)— Coil Characteristics

We developed an HTS coil for maglev applications. The magnet consists of four persistent current HTS coils and is operated at a rated temperature of 20 K and a rated magnetomotive force of 750 kA for each coil. This paper describes the fabrication and test results of each persistent current HTS coil. The HTS coil consists of 12 single-pancake coils wound with four parallel Ag-sheathed Bi2223 wires and a persistent current switch (PCS) made of YBCO thin films. The coil is conductively cooled by a cryocooler to approximately 20 K. Persistent current operating tests for four HTS coils at 750 kA were carried out and current decay rates of 0.37-0.68%/day were obtained. Mechanical vibration tests up to plusmn15 (plusmn150 m/s2) were carried out to investigate the mechanical properties of the HTS coils. Temperature increasing tests up to 25 K, which is 5 K higher than the rated operating temperature and higher magnetomotive force operating tests up to 800 kA were carried out to investigate the thermal stability of the coils and check the mechanical strength of the coils