2,050 research outputs found
Supernova dust for the extinction law in a young infrared galaxy at z = 1
We apply the supernova(SN) extinction curves to reproduce the observed
properties of SST J1604+4304 which is a young infrared (IR) galaxy at z = 1.
The SN extinction curves used in this work were obtained from models of unmixed
ejecta of type II supernovae(SNe II) for the Salpeter initial mass function
(IMF) with a mass range from 8 to 30 M_sun or 8 to 40 M_sun.
The effect of dust distributions on the attenuation of starlight is
investigated by performing the chi-square fitting method against various dust
distributions. These are the commonly used uniform dust screen, the clumpy dust
screen, and the internal dust geometry. We add to these geometries three
scattering properties, namely, no-scattering, isotropic scattering, and
forward-only scattering. Judging from the chi-square values, we find that the
uniform screen models with any scattering property provide good approximations
to the real dust geometry. Internal dust is inefficient to attenuate starlight
and thus cannot be the dominant source of the extinction.
We show that the SN extinction curves reproduce the data of SST J1604+4304
comparable to or better than the Calzetti extinction curve. The Milky Way
extinction curve is not in satisfactory agreement with the data unless several
dusty clumps are in the line of sight. This trend may be explained by the
abundance of SN-origin dust in these galaxies; SN dust is the most abundant in
the young IR galaxy at z = 1, abundant in local starbursts, and less abundant
in the Galaxy. If dust in SST J1604+4304 is dominated by SN dust, the dust
production rate is about 0.1 M_sun per SN.Comment: 12 pages, 8 figures, 1 tabl
The lipid composition and its alteration during the growth stage in pathogenic fungus, epidermophyton floccosum
Qualitative and quantitative changes of lipid components during the growth stages were studied in E. floccosum. The acyl group components of total lipids of Trichophyton rubrum and Microsporum cookei were also examined. The lipids of E. floccosum amounted to approximately 4% of the dry cell weight. Neutral lipids mainly consisted of triglycerides and sterols, and major polar lipids were phosphatidylcholine, phosphatidylethanolamine, and an unknown lipid X. The fatty acids in tryglycerides and phospholipids were palmitic, palmitoleic, stearic, oleic, and linoleic acids. The unknown polar lipid X which appeared between phosphatidylethanolamine and cardiolipin on thin layer chromatography plates contained no phosphorus. There was no significant change in the fatty acid components of E. floccosum and T. rubrum during the cell growth, whereas profound changes occurred in M. cookei. The sterol components of E. floccosum showed striking changes depending on the growth stage
A model for the infrared dust emission from forming galaxies
In the early epoch of galaxy evolution, dust is only supplied by supernovae
(SNe). With the aid of a new physical model of dust production by SNe developed
by Nozawa et al. (2003) (N03), we constructed a model of dust emission from
forming galaxies on the basis of the theoretical framework of Takeuchi et al.
(2003) (T03). N03 showed that the produced dust species depends strongly on the
mixing within SNe. We treated both unmixed and mixed cases and calculated the
infrared (IR) spectral energy distribution (SED) of forming galaxies for both
cases. Our model SED is less luminous than the SED of T03 model by a factor of
2-3. The difference is due to our improved treatment of UV photon absorption
cross section, as well as different grain size and species newly adopted in
this work. The SED for the unmixed case is found to have an enhanced near to
mid-IR (N-MIR) continuum radiation in its early phase of the evolution (age <
10^{7.25} yr) compared with that for the mixed case. The strong N--MIR
continuum is due to the emission from Si grains, which only exist in the
species of the unmixed dust production. We also calculated the IR extinction
curves for forming galaxies. Then we calculated the SED of a local starbursting
dwarf galaxy SBS 0335-052. Our present model SED naturally reproduced the
strong N--MIR continuum and the lack of cold FIR emission of SBS 0335-052. We
found that only the SED of unmixed case can reproduce the NIR continuum of this
galaxy. We then made a prediction for the SED of another typical star-forming
dwarf, I Zw 18. We also presented the evolution of the SED of LBGs. Finally, we
discussed the possibility of observing forming galaxies at z > 5.Comment: MNRAS, in press. 18 pages, 15 figures. Abstract abridge
Observation of Conduction Band Satellite of Ni Metal by 3p-3d Resonant Inverse Photoemission Study
Resonant inverse photoemission spectra of Ni metal have been obtained across
the Ni 3 absorption edge. The intensity of Ni 3 band just above Fermi
edge shows asymmetric Fano-like resonance. Satellite structures are found at
about 2.5 and 4.2 eV above Fermi edge, which show resonant enhancement at the
absorption edge. The satellite structures are due to a many-body configuration
interaction and confirms the existence of 3 configuration in the ground
state of Ni metal.Comment: 4 pages, 3 figures, submitted to Physical Review Letter
Preliminary observations on cage culture of Tilapia esculenta Graham and Tilapia xillii (Gervais) in Lake Victoria waters, at the Freshwater Fisheries Institute, Nyegezi, Tanzania
Cage culture of Tilapia is not suggested as a substitute for any known techniques in fish culture, but as one of the various techniques of obtaining more fish under controlled conditions. This fact has been very well accepted in various countries. Whererever facilities exist, this line of fish culture should be vigorously explored as a
possible avenue in increasing fish production. High density stocking, management under controlled conditions, easy technique of fabricating the cage at relatively low cost,
having no demand on land area, absence of prolific and effective breeding and easy availability of fish when a person needs it are a few of the attractions of the technique. The studies indicate that it is desirable to
have different meshes for the cages, such as, small meshed cages for rearing fry to fingerlings stages, and larger meshed cages for rearing fingerlings to table sized fishes.
II' the meshes are small, the resistance will be more and less water wilt pass through. While feeding with powdered food material, because of brisk activity of feeding fish, a part of the feed appeared wasted. This can be easily overcome if we would resort to feeding fish with cheap pelleted feeds which will no doubt reduce wastage.
Precaution has to be taken against damage of the net and thereby loss of fish and against poaching by unauthorised persons. In the present attempt has been demonstrated
the possibility of utilizing locally available species of Tilapia for cage culture and obtaining moderately satisfactory growth rates
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