837 research outputs found
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 0.1/0.2/0.4/0.8/1.6m
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 2/5/10/20m 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, 1.2, and 1.2 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
異年齢による価値観の違いに関する事例的研究 : -モラルジレンマ教材を用いた『学び合い』をもとに
「特別の教科道徳」が設置され,改めて道徳の授業で「多様な価値観を認めること」「特定の価値観を押しつけないこと」が強調された。価値観の押しつけを排除した授業方法としてモラルジレンマ教材を使った授業があるが,「教師が児童を狭い範囲でのみ思考させている」等の批判がある。その解決の一つに,様々な道徳的葛藤場面に直面したときに「ともに同意できる案を探してみないか」と考えてみる統合的思考を促す『学び合い』での道徳授業が考えられる。本研究ではどの年代でも統合的思考を促す『学び合い』での道徳授業が有効に働くか検証し,その有効性を確かめた
An extension of sine-skewed circular distributions
Sine-skewed circular distributions are identifiable and have
easily-computable trigonometric moments and a simple random number generation
algorithm, whereas they are known to have relatively low levels of asymmetry.
This study proposes a new family of circular distributions that can be skewed
more significantly than that of existing models. It is shown that a subfamily
of the proposed distributions is identifiable with respect to parameters and
all distributions in the subfamily have explicit trigonometric moments and a
simple random number generation algorithm. The maximum likelihood estimation
for model parameters is considered and its finite sample performances are
investigated by numerical simulations. Some real data applications are
illustrated for practical purposes
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
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