3,388 research outputs found
The AGN and Gas Disk in the Low Surface Brightness Galaxy PGC045080
We present radio observations and optical spectroscopy of the giant low
surface brightness (LSB) galaxy PGC 045080 (or 1300+0144). PGC 045080 is a
moderately distant galaxy having a highly inclined optical disk and massive HI
gas content. Radio continuum observations of the galaxy were carried out at 320
MHz, 610 MHz and 1.4 GHz. Continuum emission was detected and mapped in the
galaxy. The emission appears extended over the inner disk at all three
frequencies. At 1.4 GHz and 610 MHz it appears to have two distinct lobes. We
also did optical spectroscopy of the galaxy nucleus; the spectrum did not show
any strong emission lines associated with AGN activity but the presence of a
weak AGN cannot be ruled out. Furthermore, comparison of the H flux and
radio continuum at 1.4 GHz suggests that a significant fraction of the emission
is non-thermal in nature. Hence we conclude that a weak or hidden AGN may be
present in PGC 045080. The extended radio emission represents lobes/jets from
the AGN. These observations show that although LSB galaxies are metal poor and
have very little star formation, their centers can host significant AGN
activity. We also mapped the HI gas disk and velocity field in PGC 045080. The
HI disk extends well beyond the optical disk and appears warped. In the HI
intensity maps, the disk appears distinctly lopsided. The velocity field is
disturbed on the lopsided side of the disk but is fairly uniform in the other
half. We derived the HI rotation curve for the galaxy from the velocity field.
The rotation curve has a flat rotation speed of ~ 190 km/s.Comment: Paper contains 14 figures and 4 tables. Figures 8, 10 (color) and 13
supplied separately. Accepted for publication in MNRA
On feature reduction with application to electroencephalograms
Random process model and feature reduction of spontaneous and alpha frequency electroencephalogram
Interplanetary Consequences of a Large CME
We analyze a coronal mass ejection (CME) which resulted from an intense flare
in active region AR486 on November 4, 2003. The CME propagation and speed are
studied with interplanetary scintillation images, near-Earth space mission
data, and Ulysses measurements. Together, these diverse diagnostics suggest
that the internal magnetic energy of the CME determines its interplanetary
consequences.Comment: 5 pages, 9 figures, To appear in "Magnetic Coupling between the
Interior and the Atmosphere of the Sun", eds. S.S. Hasan and R.J. Rutten,
Astrophysics and Space Science Proceedings, Springer-Verlag, Heidelberg,
Berlin, 200
Night sky at the Indian Astronomical Observatory during 2000-2008
We present an analysis of the optical night sky brightness and extinction
coefficient measurements in UBVRI at the Indian Astronomical Observatory (IAO),
Hanle, during the period 2003-2008. They are obtained from an analysis of CCD
images acquired at the 2 m Himalayan Chandra Telescope at IAO. Night sky
brightness was estimated using 210 HFOSC images obtained on 47 nights and
covering the declining phase of solar activity cycle-23. The zenith corrected
values of the moonless night sky brightness in mag/square arcsecs are 22.14(U),
22.42(B), 21.28(V), 20.54(R) and 18.86(I) band. This shows that IAO is a dark
site for optical observations. No clear dependency of sky brightness with solar
activity is found. Extinction values at IAO are derived from an analysis of
1325 images over 58 nights. They are found to be 0.36 in U-band, 0.21 in
B-band, 0.12 in V-band, 0.09 in R-band and 0.05 in I-band. On average,
extinction during the summer months is slightly larger than that during the
winter months. No clear evidence for a correlation between extinction in all
bands and the average night time wind speed is found. Also presented here is
the low resolution moonless optical night sky spectrum for IAO covering the
wavelength range 3000-9300 \AA. Hanle region thus has the required
characteristics of a good astronomical site in terms of night sky brightness
and extinction, and could be a natural candidate site for any future large
aperture Indian optical-infrared telescope(s).Comment: 18 pages, 7 figures, uses basi.cls, accepted for publication in
Bulletin of the Astronomical Society of Indi
Aplicação de silicato de cálcio na cultura do arroz.
Na Embrapa Arroz e Feijão, as pesquisa sobre utilização de silicato de cálcio em arroz foram iniciadas em 1995. Apesar de recentes, as pesquisas tem obtido resultados extremamente interessantes do efeito do silicato de cálcio, tanto no aumento de rendimento de grãos e incidência de doenças, quanto na melhoria da fertilidade do solo e como condicionador de condições quimicamente favoráveis ao desenvolvimento das plantas.bitstream/CNPAF/19678/1/circ_51.pd
Review Study on Larvicidal and Mosquito Repellent Activity of Volatile Oils Isolated from Medicinal Plants
Mosquito is a vector for serious human diseases like dengue fever, hemaorrhagic dengue fever and chikungunya, .yellow fever, malaria, filaria and encephalitis among these dengue, hemaorrhagic dengue and chikungunya are highly endemic diseases in Southeast Asian and African countries, causing millions of deaths each and every year. Mosquito repellents thus play a major role in preventing man-mosquito contact and there by minimize the chance of infections and its adverse effects. The development of resistance to chemical insecticides, results rebounding vectorial capacity. Synthetic repellents are chemicals which used worldwide for protection against mosquito-borne diseases and it adversely affects the environment by contaminating water, soil and air. There is an urgent need to find alternatives to the synthetic insecticides. Plants are rich source of alternative agents for control of mosquitoes and its vectors. Extracts and isolated compounds from different plant families have been evaluated for their promising larvicidal and mosquito repellent activities. Literature has documented that essential oils and extracts have been traditionally used as effective repellents. The essential oils whose repellent activities have been demonstrated, as well as the importance of the synergistic effects among their components are the main focus of this review study. Essential oils are volatile mixtures of hydrocarbons with a diversity of functional groups, and their repellent activity has been linked to the presence of monoterpenes and sesquiterpenes. The present review study focused the larvicidal potential and mosquito repellent activity of different volatile oils of medicinal plants. From an economical point of view synthetic chemical is still more frequently used as repellents than essential oils; these essential oils have the potential to provide efficient and can be used as a cheap, eco-friendly, safer for humans and the environment and also efficient alternative to the chemical larvicides
Optical Photometry of the GRB 010222 Afterglow
The optical afterglow of GRB 010222 was observed using the recently installed
2-m telescope at the Indian Astronomical Observatory, Hanle, and the telescopes
at the Vainu Bappu Observatory, Kavalur, beginning ~ 0.6 day after the
detection of the event. The results based on these photometric observations
combined with others reported in the literature are presented in this paper.
The R band light curve shows an initial decline of intensities proportional to
t^{-0.542} which steepens, after 10.3 hours, to t^{-1.263}. Following the model
of collimated outflow, the early break in the light curve implies a very narrow
beam angle (~ 2-3 deg). The two decay rates are consistent with the standard
jet model in a uniform density ambient medium, but require a hard spectrum of
electron power density with p ~ 1.5. The R band light between 14 and 17 hours
since outburst departs from the power law fit by 0.1 mag and shows some
evidence for fluctuations over timescales of an hour in the observer's frame.
Such deviations are expected due to density inhomogeneities if the ambient
medium is similar to the local interstellar medium. GRB 010222 is thus an
example of a highly collimated outflow with a hard spectrum of electron energy
distribution in normal interstellar environment.Comment: 15 pages, Latex, including 2 postscript figures, to appear in the
Bull. astro. Soc. India, September 2001 issu
Pharmacognostic and Phytochemical Analysis of Asystasia Variabilis Trim. - An Extrapharmacopoeal Ayurvedic Medicinal Plant
Background - Asystasia Variabilis Trim. also known as Maithaala Kaddi by traditional practitioners of Udupi. Belonging to the family Acanthaceae. Is a semi-scandent herb, and effectively used by the Folklore practitioners for the management of Amlapitta (acid peptic disorder), worm infestations and rheumatism. Aim - To explore the pharmacognostical and preliminary phytochemical parameters of plant to standardize the drug. Materials and Methods - whole mature plant of A.variabilis was collected from Udupi district. Macroscopic, microscopic physico-chemical standards, HPTLC and secondary metabolites screening were scientifically recorded. Results - The pharmacognostical leaf study has shown single layered epidermis throughout midrib and lamina. Anatomical features of stem exhibit single layer of epidermis covered with trichomes. Inner to this, densely arranged collenchyma cells are present. In transverse section of root showed epidermal layer is surrounded by root hairs which are abundant. Powder microscopy characteristics showed the presence of starch in parenchyma region, mesophyll cells with stomata and sclerides were present. The standard out print of the drug is represented by physicochemical standards and HPTLC. Preliminary Phytochemical study shows that it contains Alkaloids, Carbohydrates, Steroids, Tannins and Phenol. Conclusion - Pharmacognostical study carried out on A.variabilis showed quality standards of the drug, with respect to its macroscopy, microscopy, physico-chemical standards and HPTLC
- …