Development of solid-lubricated ball-screws for use in space

Ball-screws lubricated by solid lubricant films containing molybdenum disulphide are developed. The ball-screws (shaft diameter: phi 25 mm, length: 667 mm) were operated under a load of 40 to 120 N at a speed of 1.5 to 200 rpm at 10(exp -5) Pa. First, ball-screws made of stainless steel SUS 440C were studied using test equipment originally designed for this study. To reduce weight, the next step taken was to develop a ball-screw made of 6Al-4V-titanium. Long wear-life of more than 1 x 10(exp 7) revolutions was achieved with solid lubricated ball-screws made of SUS 440C and 6Al-4V-titanium in a hard vacuum. According to the surface profile of the shaft measured after 1 x 10(exp 7) revolutions, more solid lubricant remained on the surface of 6Al-4V-titanium than that of stainless steel. Auger and EPMA analysis confirmed lubrication was maintained by solid lubricant on nuts and screws after the lubricant films on the balls were worn off

Electromagnetic probes for critical fluctuations of phase transitions in dense QCD

We study how the dilepton production rates and electric conductivity are affected by the phase transition to color superconductivity and the QCD critical point. Effects of the soft modes associated with these phase transitions are incorporated through the photon self-energy called the Aslamazov-Larkin, Maki-Thompson, and density-of-states terms, which are responsible for the paraconductivity in metallic superconductors. We show that anomalous enhancements of the production rate in the low energy/momentum region and the conductivity occur around the respective critical points

Phase Separation of Multi-Component Bose-Einstein Condensates of Trapped Atoms and Molecules with a Homonuclear Feshbach Resonance

We investigate phase separation of Bose-Einstein condensates (BECs) of two-component atoms and one-component molecules with a homonuclear Feshbach resonance. We develop a full model for dilute atomic and molecular gases including correlation of the Feshbach resonance and all kinds of interparticle interactions, and numerically calculate order parameters of the BECs in spherical harmonic oscillator traps at zero temperature with the Bogoliubov's classical field approximation. As a result, we find out that the Feshbach resonance can induce two types of phase separation. The actual phase structures and density profiles of the trapped gases are predicted in the whole parameter region, from the atom dominant regime to the molecule dominant regime. We focus on the role of the molecules in the phase separation. Especially in the atom dominant regime, the role of the molecules is described through effective interactions derived from our model. Furthermore we show that a perturbative and semi-classical limit of our model reproduces the conventional atomic BEC (single-channel) model.Comment: 11pages, 4 figure

Dyspnoea with activities of daily living versus peak dyspnoea during exercise in male patients with COPD

SummaryDyspnoea measurements in chronic obstructive pulmonary disease (COPD) can be broadly divided into two categories: those that assess breathlessness during exercise, and those that assess breathlessness during daily activities. We investigated the relationships between dyspnoea at the end of exercise and during daily activities with clinical measurements and mortality in COPD patients.We examined 143 male outpatients with moderate to very severe COPD. The peak Borg score at the end of progressive cycle ergometry was used for the assessment of peak dyspnoea rating during exercise, and the Baseline Dyspnea Index (BDI) score was used for dyspnoea with activities of daily living. Relationships between these dyspnoea ratings with other clinical measurements of pulmonary function, exercise indices, health status and psychological status were then investigated. In addition, their relationship with the 5-year mortality of COPD patients was also analyzed to examine their predictive ability.Although the BDI score was significantly correlated with airflow limitation, diffusing capacity, exercise indices, health status and psychological status, the Borg score at the end of exercise had non-existent or only weak correlations with them. The BDI score was strongly significantly correlated with mortality, whereas the Borg score was not.Dyspnoea during daily activities was more significantly correlated with objective and subjective measurements of COPD than dyspnoea at the end of exercise. In addition, the former was more predictive of mortality. Dyspnoea with activities of daily living is considered to be a better measurement for evaluating the disease severity of COPD than peak dyspnoea during exercise