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While there have been many surveys for luminous, blue galactic stars and their numbers can be considered somewhat complete, such is not the case for red supergiants (see e.g. Humphreys and McElroy 1984). One result of this incompleteness is that the ratios B/R and WR/R, often used as diagnostics for evolutionary models of massive stars and the variation of the ratios with galactocentric distance, are not well known for the Galaxy. In an attempt to improve the statistics, the first author began an objective-prism survey within 6 deg of the southern galactic plane using I-N plates. The dispersion is 3400 A/mm at the A-band, and the spectra cover the range 6800–8800 A; the deepest plates reach ir mag ∼13. The detection of possible M supergiants on such plates was first discussed by Nassau, et al. (1954) and depends on the presence of TiO at 7054 A and a spectrum sharply tapered to the blue. For supergiants, this shape results from integration of interstellar dust over a long path-length, but any sample of red stars with tapered spectra contains M giants in heavily-obscured regions and S stars; thus follow-up observations of the candidate stars are necessary.
We have completed a grid of spherically symmetric AGB star atmospheres using the state of the art spectral synthesis code PHOENIX. Models are constructed for stars with masses of 1 M⊙ and 1.5 M⊙, spanning the range 10 to 3300 L⊙ in luminosity and 2500 to 5200 K in effective temperature. We find that grains of Al2O3 and CaTiO3 among other species form in atmospheres cooler than Teff = 3000 K. In the coolest models the grains cause a weakening of the TiO absorption features in the red and near infrared of up to 30% through both a depression of the continuum and a depletion of the TiO number abundance. We use spectrophotometric observations from a number of catalogs to determine effective temperature – spectral class and effective temperature – color relationships. We also compare synthetic colors calculated from our models with observations of M giants on Wing's 8-color narrow-band system of classification photometry.
Spectra at 16 - 45 μm of several regions within the central 80″ of the Galaxy have been obtained at 20″ resolution using the Goddard Cryogenic Grating Spectrometer No. 2 on the Kuiper Airborne Observatory. A broad band of excess emission extending from 24 to 45 μm is present in the spectra at positions covering the “tongue” and the inner edge of the circumnuclear disk. A similar dust emission feature has been observed in some carbon-rich evolved stars and in a nitrogen-rich evolved massive star. The observations reported here are the first detection of this dust emission feature in the interstellar medium. After considering several possible candidates of the carrier for this 30 μm dust feature, we find that MgS is the best owing to its good fit to the observed spectra. The origin of this ~ 30 μm feature in the Galactic center is unknown. Based on the theoretical results of dust condensation and elemental abundances in a supernova, we find that the supernovae in the central 500 pc could provide the amount of MgS dust, which we proposed as the carrier of the 30 μm dust feature, observed in the central 3 pc.
In this work, the deposition and photocatalytic response of V2O5 thin films modified with different amounts of Ag (Ag:V2O5) is reported. Films were deposited on glass and silicon substrates (100), using the pulsed laser deposition (PLD) technique. A high purity vanadium target, with a different number of silver pellets attached on it were used. Thin films were characterized by energy dispersive spectroscopy (EDS) to determine the elemental chemical composition; structural changes due to the addition of Ag were monitored by Raman spectroscopy; Optical microscopy was used to observe the surface morphology and UV-Vis spectroscopy was employed to determine optical properties. Photocatalytic response of the prepared films was studied through the degradation of a malachite green solution using a solar irradiation source.
Temperature classes based on photometric measurements of the 7100 Å band of TiO are compared with published spectroscopic classifications by various investigators. Dwarfs, giants, and supergiants are treated separately. The photometric types are in excellent agreement with types given by P. C. Boeshaar for M dwarfs and by P. C. Keenan and Y. Yamashita for M giants. In all other cases the scatter is larger. The usefulness of the types given by various authors for dwarfs and giants is tested by examining their correlation with color temperature determined by narrow-band photometry.
A summary is given of the molecular bands occurring in the near-infrared spectra of cool stars, especially those having sufficient strength and freedom from contamination to be measurable by narrow-band photometry. In some cases useful indices of both temperature and luminosity can be obtained from such measurements. Several bands remain unidentified, including the 9910 Å band in late M dwarfs and at least nine bands in cool S stars.
Three topics of a spectroscopic nature are discussed. (1) In Mira variables, grossly different spectral types are sometimes obtained from zero-volt and excited TiO bands of the same band system. (2) A few M stars have been found to show bands of’ both VO and CN at the same time. They may be the coolest known supergiants, although there remains some doubt as to their luminosities. (3) The first results are given from a program of measuring crude C12/C13 ratios from narrow-band photometry of sensitive points on the profile of the ∆υ = + 2 band sequence of CN. The observations require only a few minutes per star, and the method can be applied to G and K giants and supergiants as well as to carbon stars.
Spectral types based upon photoelectric measurements of the strong TiO band near 7100 Å and having an internal accuracy of one-tenth of a subclass are presented for 26 dwarf stars in the range K4 to M6. For the calibration of the TiO index into spectral type, the MK scale for giants established by Wing and Keenan was adopted. Accordingly the types differ systematically from those previously published on any of the systems used for dwarfs, being closest to Joy's. The advantages of the MK giant scale are discussed, and it is suggested that the stars classified here be adopted as standards for a revised system of MK classification for dwarfs.
The relation between TiO band strength and near-infrared color temperature for dwarfs differs significantly from the giant relation. The coolest dwarfs observed were Wolf 359 and Proxima Centauri; although Wolf 359 is both cooler and less luminous than Proxima, they have nearly identical TiO band strengths.
This paper reports the synthesis and characterization of the ZrO2:Co nanosystem, by incorporation of Co nanoparticles (CoNP) into tetragonal and monoclinic zirconia. ZrO2 was synthesized by a sol-gel process, while cobalt nanoparticles were obtained through a colloidal method by chemical reduction of a metal precursor. CoNP were incorporated by two different approaches: during the synthesis of the ZrO2 and by classical impregnation of CoNP on zirconium oxide. The size of Cobalt nanoparticles was controlled through the concentration of reducing agent (NaBH4) and passivanting agent (1-dodecanethiol). According to SEM and TEM analysis, the diameter of the zirconium oxide particles depends on the CoNP concentration added; the particle size for pure zirconia treated at 500°C is 200 nm and 180 nm for ZrO2:Co. X-Ray diffraction showed presence of the tetragonal and monoclinic zirconia, but the abundance of each one depends on the Co nanoparticles and thermally treatment.
Assessments of some of the symptoms and behaviour problems of long-term psychiatric patients living in the community were obtained independently from clinical interviews with such patients, and from interviews with day staff, residential staff and families caring for them. In general, interviews with residential staff and family members revealed much higher levels of symptoms and behaviour problems than either of the other two interviews. These findings have implications for research and clinical practice including the fact that adequate assessments should include the testimony of family or residential staff.
An indentation-strength formulation is presented for nontransforming ceramic materials that show an increasing toughness with crack length (T curve, or R curve) due to the restraining action of interfacial bridges behind the crack tip. By assuming a stress-separation function for the bridges a microstructure-associated stress intensity factor is determined for the penny-like indentation cracks. This stress intensity factor opposes that associated with the applied loading, thereby contributing to an apparent toughening of the material, i.e., the measured toughness in excess of that associated with the intrinsic cohesion of the grain boundaries (intergranular fracture). The incorporation of this additional factor into conventional indentation fracture mechanics allows the strengths of specimens with Vickers flaws to be calculated as a function of indentation load. The resulting formulation is used to analyze earlier indentation-strength data on a range of alumina, glass-ceramic, and barium titanate materials. Numerical deconvolution of these data determines the appropriate T curves. A feature of the analysis is that materials with pronounced T curves have the qualities of flaw tolerance and enhanced crack stability. It is suggested that the indentation-strength methodology, in combination with the bridging model, can be a powerful tool for the development and characterization of structural ceramics, particularly with regard to grain boundary structure.
One of the chief problems mentioned by the relatives of people suffering from schizophrenia is the difficulty in obtaining factual and practical advice. Many have struggled on for years, using trial-and-error methods, without knowing whether their lack of success was due to the immutable course of events, to ignorance, or to a deficiency in themselves of the ability to care. Some have made tentative enquiries but have been given a more or less polite brush-off. Although most relatives, like most sufferers, do eventually become aware of the diagnosis, it is rare for them to be given this information as part of a long-term plan of management which they are invited to share with professional staff and patient, and even more unusual for them to be told early in the course of the disorder.