Comparative study of manufacturing techniques for coronagraphic binary pupil masks: masks on substrates and free-standing masks

We present a comparative study of the manufacture of binary pupil masks for coronagraphic observations of exoplanets. A checkerboard mask design, a type of binary pupil mask design, was adopted, and identical patterns of the same size were used for all the masks in order that we could compare the differences resulting from the different manufacturing methods. The masks on substrates had aluminum checkerboard patterns with thicknesses of 0.1/0.2/0.4/0.8/1.6$\mu$m constructed on substrates of BK7 glass, silicon, and germanium using photolithography and chemical processes. Free-standing masks made of copper and nickel with thicknesses of 2/5/10/20$\mu$m were also realized using photolithography and chemical processes, which included careful release from the substrate used as an intermediate step in the manufacture. Coronagraphic experiments using a visible laser were carried out for all the masks on BK7 glass substrate and the free-standing masks. The average contrasts were 8.4$\times10^{-8}$, 1.2$\times10^{-7}$, and 1.2$\times10^{-7}$ for the masks on BK7 substrates, the free-standing copper masks, and the free-standing nickel masks, respectively. No significant correlation was concluded between the contrast and the mask properties. The high contrast masks have the potential to cover the needs of coronagraphs for both ground-based and space-borne telescopes over a wide wavelength range. Especially, their application to the infrared space telescope, SPICA, is appropriate.Comment: 21 pates, 12 figures, 2 tables, accepted to PAS

Histological Analysis of Failed Cartilage Repair after Marrow Stimulation for the Treatment of Large Cartilage Defect in Medial Compartmental Osteoarthritis of the Knee

Bone marrow-stimulating techniques such as microfracture and subchondral drilling are valuable treatments for full-thickness cartilage defects. However, marrow stimulation-derived reparative tissues are not histologically well-documented in human osteoarthritis. We retrospectively investigated cartilage repairs after marrow stimulation for the treatment of large cartilage defects in osteoarthritic knees. Tissues were obtained from patients who underwent total knee arthroplasty (TKA) after arthroscopic marrow stimulation in medial compartmental osteoarthritis. Clinical findings and cartilage repair were assessed. Sections of medial femoral condyles were histologically investigated by safranin O staining and anti-type II collagen antibody. Marrow stimulation decreased the knee pain in the short term. However, varus leg alignment gradually progressed, and TKA conversions were required. The grade of cartilage repair was not improved. Marrow stimulations resulted in insufficient cartilage regeneration on medial femoral condyles. Safranin O-stained proteoglycans and type II collagen were observed in the deep zone of marrow-stimulated holes. This study demonstrated that marrow stimulation resulted in failed cartilage repair for the treatment of large cartilage defects in osteoarthritic knees. Our results suggest that arthroscopic marrow stimulation might not improve clinical symptoms for the long term in patients suffering large osteoarthritic cartilage defects

Multi-Color Coronagraph Experiment in a Vacuum Testbed with a Binary Shaped Pupil Mask

We conducted a number of multi-band coronagraph experiments using a vacuum chamber and a binary-shaped pupil mask which in principle should work at all wavelengths, in the context of the research and development on a coronagraph to observe extra-solar planets (exoplanets) directly. The aim of this work is to demonstrate that subtraction of Point Spread Function (PSF) and multi-band experiments using a binary-shaped pupil mask coronagraph would help improve the contrast in the observation of exoplanets. A checkerboard mask, a kind of binary-shaped pupil mask, was used. We improved the temperature stability by installing the coronagraph optics in a vacuum chamber, controlling the temperature of the optical bench, and covering the vacuum chamber with thermal insulation layers. We evaluated how much the PSF subtraction contributes to the high contrast observation by subtracting the images obtained through the coronagraph. We also carried out multi- band experiments in order to demonstrate a more realistic observation using Super luminescent Light Emitting Diodes (SLEDs) with center wavelengths of 650nm, 750nm, 800nm and 850nm. A contrast of 2.3x10-7 was obtained for the raw coronagraphic image and a contrast of 1.3x10-9 was achieved after PSF subtraction with a He-Ne laser at 632.8nm wavelength. Thus, the contrast was improved by around two orders of magnitude from the raw contrast by subtracting the PSF. We achieved contrasts of 3.1x10-7, 1.1x10-6, 1.6x10-6 and 2.5x10-6 at the bands of 650nm, 750nm, 800nm and 850nm, respectively, in the multi-band experiments. The results show that contrast within each of the wavelength bands was significantly improved compared with non-coronagraphic optics. We demonstrated PSF subtraction is potentially beneficial for improving contrast of the coronagraph, and this coronagraph produces a significant improvement in contrast with multi-band light sources.Comment: 14 pages, 7 figures, accepted for publication in PAS

Addition of Some Transition Elements and their Effects on the Electrochemical Properties of MgNi

In this study, some transition elements, Ag, Co, Pd, Re, Ru and Ti, at 6 and 10mol% compositions, were selected to ball mill with Mg2Ni and Ni, and the effects of transition elements on the electrochemical properties of amorphous MgNi were investigated. Three distinct effects on the electrochemical properties of MgNi were found: Ti and Pd dissolved into the bulk of MgNi during ball milling and the degradation of discharge capacity was decreased by addition of Ti and Pd. Ag and Co also dissolved in the MgNi powder, but there was no appreciable influence on the electrochemical behavior of MgNi. Re and Ru neither dissolved into MgNi nor improved the properties of MgNi

Effects of Pd Addition on the Electrochemical Properties of MgNi

Two groups of Pd-modified MgNi samples were prepared: sample Ⅰ, ball-milling Pd (1, 6 and 10 mol%) with amorphous MgNi for 10 min, 2hr or 10 hr, sample Ⅱ, ball-milling 10 mol% Pd with Mg2Ni and Ni for 80 hr. Effects of the addition of Pd on the electrochemical properties of MgNi were investigated. For sample Ⅰ, the effects of Pd depended on both the Pd ratio and the time of ball-milling. During ball-milling, Pd bebame amorphous and was distributed uniformly on the surface of MgNi particle. At 6 mol% and 10 mol% Pd, degradation of the discharge capacity of MgNi was significantly decreased. As for sample Ⅱ, the cycle life of MgNi was remarkably improved by Pd modification. The roles of Pd in the behavior of MgNi were analyzed, and the improvements in MgNi properties arising from both modifications by Pd were thought to be due to the prevention of the formation of Mg(OH)2