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Measurements in the infrared wavelength domain allow direct assessment of the physical state and energy balance of cool matter in space, enabling the detailed study of the processes that govern the formation and evolution of stars and planetary systems in galaxies over cosmic time. Previous infrared missions revealed a great deal about the obscured Universe, but were hampered by limited sensitivity.
SPICA takes the next step in infrared observational capability by combining a large 2.5-meter diameter telescope, cooled to below 8 K, with instruments employing ultra-sensitive detectors. A combination of passive cooling and mechanical coolers will be used to cool both the telescope and the instruments. With mechanical coolers the mission lifetime is not limited by the supply of cryogen. With the combination of low telescope background and instruments with state-of-the-art detectors SPICA provides a huge advance on the capabilities of previous missions.
SPICA instruments offer spectral resolving power ranging from R ~50 through 11 000 in the 17–230 μm domain and R ~28.000 spectroscopy between 12 and 18 μm. SPICA will provide efficient 30–37 μm broad band mapping, and small field spectroscopic and polarimetric imaging at 100, 200 and 350 μm. SPICA will provide infrared spectroscopy with an unprecedented sensitivity of ~5 × 10−20 W m−2 (5σ/1 h)—over two orders of magnitude improvement over what earlier missions. This exceptional performance leap, will open entirely new domains in infrared astronomy; galaxy evolution and metal production over cosmic time, dust formation and evolution from very early epochs onwards, the formation history of planetary systems.
Using mainly the overwintering prepupae of a “ slug caterpiller ”, Cnidocampa flavescens (Walk.), the mechanism for the frost-resistance in insects was investigated.
Though the freezing point of the blood shows the value of about −2°C. the prepupae are very readily supercooled. When cooled below −20°C., however, the insect body suddenly congeals hard. Insects frozen thus, even for a long period of 100 days, usually withstand the solidification of their bodies without any harmful effect upon either the further development or upon the next generation.
Judging from the shape of the freezing curves of the prepupae and the freezing processes of the blood and isolated tissues, it is inferred that the most probable freezing process of the caterpillar is as follows. At first, the blood freezes rapidly, and consequently the grade of supercooling of the tissue cells is very much lessened by the latent heat of fusion of ice. Extra-cellular freezing of the tissue cells then takes place, in which case the properties of the blood as well as some property of the plasmic surface layer of the cells may play an important role in the prevention of the transmission of freezing into the cell. With the advance of the blood freezing, the tissue cells undergo dehydration and contraction; neverthless, they usually withstand such a condition for a long period, provided that the freezing temperature is not too low. Consequently, the so-called anabiotic state of a frozen insect does not necessarily mean the destruction of the cell structure.
We identified pepsinogen C (PGC) gene polymorphisms by means of
which amplified DNA
in the region within the intron between exons 7 and 8, and by 6% polyacrylamide
Six alleles were found in a Japanese population. The frequencies of these
alleles in 408 unrelated
Japanese individuals were 0·074, 0·026, 0·335, 0·237,
0·016 and 0·314, respectively. The serum
pepsinogen II level significantly decreased in the order of the allele
homozygote, the allele 6
heterozygote and the other genotypes (χ2=7·850,
D.F.=2, p=0·020). These findings indicated that
the genetic background of serum pepsinogen should be considered when
screening for stomach cancer by this procedure.
The microstructure of pressureless sintered silicon carbide (SiC) materials with alumina (Al2O3) addition was investigated using analytical electron microscopy and nuclear magnetic resonance. A sintered body with a density of higher than 99% theoretical was obtained with an addition of 5 wt.% Al2O3. The sintered body (SiC–Al2O3) has high strength, high fracture toughness, and high fatigue resistance. Its fracture toughness is approximately 5 MPa-m1/2, which is twice as high as that of pressureless sintered SiC materials with boron and carbon additions (SiC–B–C). The correlation between the microstructure and the mechanical properties is presented here. The starting β–SiC powder is mostly transformed to α–SiC with various polytype distributions during the sintering process. The microstructure has homogeneously distributed, fine, plate-like interlocking gains with a high aspect ratio. Well-developed basal planes form parallel and elongated boundaries, and the crystal structure is mostly the 6H polytype (56%) mixed with thin lamellar 4H.
Silicon carbide materials with BeO addition (2 wt%) have the unique properties of high electrical resistivity, high thermal conductivity, and a thermal expansion coefficient close to that of silicon. The materials have been used as a chip carrier material for high power LSI packaging. Microstructures were correlated by means of analytical electron microscopy (AEM), with the physical properties. Generally, BeO particles are evenly distributed mostly at triple points and the grain growth is anisotropic and many grains are elongated with an aspect ratio of 2 or 3. The average grain size is measured to be around 5 μm and the morphology is typically thick tabular.
AEM analysis has shown that large middle section of each SiC grain is mostly 6H polytype with a few or no stacking faults. On both sides of the 6H polytype, sheaths are formed, which consist of a large number of extremely thin 4H or other polytype lamellae. Along grain boundaries, no second phase formation is observed with a few exception of Be 2 C and impurity transition metal compounds lamellar formation.
The results indicate that direct and clean contacts between 6H lamellae and BeO grain or other 6H lamellae form a path of high thermal conductivity. On the other hand, complex network of thin disordered (4H rich) lamellae doped with BeO forms the electrically high resistive path.
Mechanical abrasion has been used by the authors to prepare a variety of materials, mainly ceramics, which have been thinned to electron transparency. The basic premise of this technique is the rotation of a spherically shaped wood tool at right angles to a rotating 3mm specimen disk (∼100 μm thick). A slurry of 1/2 μm diamond powder in a glycerin vehicle thins the specimen and carries away the abraded matter. In addition to the wood tool other materials such as brass, teflon and polyethylene have been tried without success. Abrasion “marks” left on the thin specimen surface can be ignored in some situations or removed by a touch up ion milling at 3 keV for ∼1/2 hr. Recently, attempts to thin N+ implanted Al from the un-implanted side using a wood tool were found to be extremely time consuming, i.e. 60 hr or more. It was found that a spherical stainless steel tool produced a suitably thin transmission electron microscopy (TEM) specimen using glycerin as the vehicle and no diamond powder. Depending upon the pressure applied to the tool these specimens could be thinned in as little as 3 hr. The turning marks left by the lathe tool proved to be sufficient to thin the soft aluminum. From this result It appears that soft tools will thin hard materials and hard tools can be used to thin soft materials efficiently. A number of other specimens recently prepared using mechanical microthinning will also be presented.
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