1,526 research outputs found
Reduction of polyphenolic exudation and enhancement of hardening efficiency in pomegranate tissue culture plants
140-147Punica granatum is one of the world’s nutritious fruit, tolerating high drought. Bacterial blight is being an obstruct in the export of pomegranate from India. In the present study, a rigorous and efficient protocol for micropropagation of pomegranate plantlets is developed which can replace traditional plant breeding practices. Antioxidants controls polyphenolic exudation in micropropagation. For the first time, this report accomplishes to control polyphenols by modifying medium constituents. Woody plant (WP) medium containing benzyl-amino-purine (BAP) and kinetin (both at 1.5 mg l-1) exhibited high bud break of about 99%. Further, it gave highest number of shoots of about 6.36 ± 0.22 with the length 6.12 ± 0.31 cm in multiplication stage. Shoots were successfully rooted in WP medium containing indole butyric acid (IBA) 1.5 mg l-1 with 5.62 ± 0.17 roots. This research emphasizes to preliminarily harden plant lets in vitro prior to hardening using innovative technique with increase in gelling strength and by creating nutrient competition. Nutrient stressed plants have a higher survival rate of 98% and water stressed plants have a survival rate of 96% when compared to conventional method. Therefore, mass propagation of pomegranate plants is possible to meet the demand of farmers in procuring disease-free plantlets
Outflow and dense gas emission from massive Infrared Dark Clouds
Infrared Dark Clouds are expected to harbor sources in different, very young
evolutionary stages. To better characterize these differences, we observed a
sample of 43 massive Infrared Dark Clouds, originally selected as candidate
high-mass starless cores, with the IRAM 30m telescope covering spectral line
tracers of low-density gas, high-density gas, molecular outflows/jets and
temperature effects. The SiO(2-1) observations reveal detections toward 18
sources. Assuming that SiO is exclusively produced by sputtering from dust
grains, this implies that at least in 40% of this sample star formation is
on-going. A broad range of SiO line-widths is observed (between 2.2 and
65km/s), and we discuss potential origins for this velocity spread. While the
low-density tracers 12CO(2-1) and 13CO(1-0) are detected in several velocity
components, the high-density tracer H13CO+(1--0) generally shows only a single
velocity component and is hence well suited for kinematic distance estimates of
IRDCs. Furthermore, the H13CO+ line-width is on average 1.5 times larger than
that of previously observed NH3(1,1). This is indicative of more motion at the
denser core centers, either due to turbulence or beginning star formation
activity. In addition, we detect CH3CN toward only six sources whereas CH3OH is
observed toward approximately 40% of the sample. Estimates of the CH3CN and
CH3OH abundances are low with average values of 1.2x10^{-10} and 4.3x10^{-10},
respectively. These results are consistent with chemical models at the earliest
evolutionary stages of high-mass star formation. Furthermore, the CH3OH
abundances compare well to recently reported values for low-mass starless
cores.Comment: 22 pages (ApJ referee style), 7 figures, accepted for Ap
High-Mass Proto-Stellar Candidates - II : Density structure from dust continuum and CS emission
We present a detailed 1.2 mm continuum and CS spectral line study of a large
sample of 69 massive star forming regions in very early stages of evolution,
most of them prior to building up an ultracompact HII region. The continuum
data show a zoo of different morphologies and give detailed information on the
spatial distributions, the masses, column densities and average densities of
the whole sample. Fitting the radial intensity profiles shows that three
parameters are needed to describe the spatial distribution of the sources:
constant emission from the center out to a few arcsec radius followed by a
first power law intensity distribution which steepens further outside into a
second power law distribution. The mean inner power law intensity index mi
(I~r^(-mi)) is 1.2 corresponding to density indices p (n~r^(-p)) of 1.6. In
total the density distribution of our massive star formations sites seem to be
not too different from their low-mass counterparts, but we show that setting
tight constrains on the density indices is very difficult and subject to many
possible errors. The local densities we derive from CS calculations are higher
(up to one order of magnitude) than the mean densities we find via the
mm-continuum. Such inhomogeneous density distribution reflects most likely the
ubiquitous phenomenon of clumping and fragmentation in molecular clouds.
Linewidth-mass relations show a departure from virial equilibrium in the stages
of strongly collapsing cores.Comment: 15 pages, 13 jpeg-figures. Astrophysical Journal, in pres
Physical properties of Southern infrared dark clouds
It is commonly assumed that cold and dense Infrared Dark Clouds (IRDCs)
likely represent the birth sites massive stars. Therefore, this class of
objects gets increasing attention. To enlarge the sample of well-characterised
IRDCs in the southern hemisphere, we have set up a program to study the gas and
dust of southern IRDCs. The present paper aims at characterizing the continuuum
properties of this sample of objects. We cross-correlated 1.2 mm continuum data
from SIMBA@SEST with Spitzer/GLIMPSE images to establish the connection between
emission sources at millimeter wavelengths and the IRDCs we see at 8 m in
absorption against the bright PAH background. Analysing the dust emission and
extinction leads to a determination of masses and column densities, which are
important quantities in characterizing the initial conditions of massive star
formation. The total masses of the IRDCs were found to range from 150 to 1150
(emission data) and from 300 to 1750 (extinction
data). We derived peak column densities between 0.9 and 4.6
cm (emission data) and 2.1 and 5.4 cm
(extinction data). We demonstrate that the extinction method fails for very
high extinction values (and column densities) beyond A values of
roughly 75 mag according to the Weingartner & Draine (2001) extinction relation
model B. The derived column densities, taking into account
the spatial resolution effects, are beyond the column density threshold of 3.0
cm required by theoretical considerations for massive
star formation. We conclude that the values for column densities derived for
the selected IRDC sample make these objects excellent candidates for objects in
the earliest stages of massive star formation.Comment: Accepted for publication in Astronomy & Astrophysic
Study on Efficacy of Expired and Active Forms of Various Antibiotics on Saccharomyces cerevisiae
Antibiotics are among the most frequently prescribed medications in modern medicines. The cell protection strategies in the organisms, development of resistance in previously susceptible microbes, the inevitable progression of microbes exposed to antibiotics to develop resistance, were the nesisities that ensures the need for continual cycles of discovery and development of new antibiotics. A large variety of antibiotics are available in the drug market today, several others being added regularly in combat with various pathogens that cause disease in humans as well as in animals. Our present study focused to investigate the change in efficacy of commonly used antibiotics such as amoxicillin, ampicillin, sparfloxacin, cefixime. We have collected antibiotics with before and after their expiry dates. A simple eukaryotic model organism Saccharomyces cerevisiae is used to study the comparative understanding of this microbe with these different antibiotics. In our investigation we found that response of Sacchromyces cerevisiae towards different antibiotics varied in its intricacies. Fresh forms of antibiotics have significantly inhibiting the growth of Saccharomyces cerevisiae as compared to expired forms. The observations revealed that expired forms of antibiotics loose their efficacy drastically
The RMS Survey: 6 cm continuum VLA observations towards candidate massive YSOs in the northern hemisphere
(Abridged) Context: The Red MSX Source (RMS) survey is an ongoing
multi-wavelength observational programme designed to return a large,
well-selected sample of massive young stellar objects (MYSOs). We have
identified 2000 MYSO candidates located throughout the Galaxy by
comparing the colours of MSX and 2MASS point sources to those of known MYSOs.
Aims: To identify the populations of UCHII regions and PNe within the sample
and examine their Galactic distribution. Method: We have conducted high
resolution radio continuum observations at 6 cm towards 659 MYSO candidates in
the northern hemisphere (10\degr< l < 250\degr) using the VLA. In addition to
these targeted observations we present archival data towards a further 315 RMS
sources extracted from a previous VLA survey of the inner Galaxy. Results: We
find radio emission towards 272 (27% of the observed sample). Using
results from other parts of our multi-wavelength survey we separate these
RMS-radio associations into two distinct types of objects, classifying 51 as
PNe and a further 208 as either compact or UC HII regions. Using this well
selected sample of HII regions we estimate their Galactic scale height to be
0.6\degr. Conclusions: Using radio continuum and archival data we have
identified 79 PNe and 391 HII regions within the northern RMS catalogue. We
estimate the total fraction of contamination by PNe in the RMS sample is of
order 10%. The sample of HII regions is probably the best representation to
date of the Galactic population of HII regions as a whole.Comment: Accepted for publication in Astronomy and Astrophysics. 15 pages, 9
figures and 5 tables. Full versions of Tables 3, 4 and 5 and Figs. 2, 4 and 7
will only be available via CDS or the RMS website at
http:/www.ast.leeds.ac.uk/cgi-bin/RMS/RMS_VLA_IMAGES.cg
Structure and Colors of Diffuse Emission in the Spitzer Galactic First Look Survey
We investigate the density structure of the interstellar medium using new
high-resolution maps of the 8 micron, 24 micron, and 70 micron surface
brightness towards a molecular cloud in the Gum Nebula, made as part of the
Spitzer Space Telescope Galactic First Look Survey. The maps are correlated
with 100 micron images measured with IRAS. At 24 and 70 micron, the spatial
power spectrum of surface brightness follows a power law with spectral index
-3.5. At 24 micron, the power law behavior is remarkably consistent from the
0.2 degree size of our maps down to the 5 arcsecond spatial resolution. Thus,
the structure of the 24 micron emission is self-similar even at milliparsec
scales. The combined power spectrum produced from Spitzer 24 micron and IRAS 25
micron images is consistent with a change in the power law exponent from -2.6
to -3.5. The decrease may be due to the transition from a two-dimensional to
three-dimensional structure. Under this hypothesis, we estimate the thickness
of the emitting medium to be 0.3 pc.Comment: 13 Pages, 3 Figures, to be published in Astrophysical Journal
Supplement Series (Spitzer Special Issue), volume 154. Uses aastex v5.
High-Mass Proto-Stellar Candidates - I : The Sample and Initial Results
We describe a systematic program aimed at identifying and characterizing
candidate high-mass proto-stellar objects (HMPOs). Our candidate sample
consists of 69 objects selected by criteria based on those established by
Ramesh & Sridharan (1997) using far-infrared, radio-continuum and molecular
line data. Infrared-Astronomical-Satellite (IRAS) and
Midcourse-Space-Experiment (MSX) data were used to study the larger scale
environments of the candidate sources and to determine their total luminosities
and dust temperatures. To derive the physical and chemical properties of our
target regions, we observed continuum and spectral line radiation at millimeter
and radio wavelengths. We imaged the free-free and dust continuum emission at
wavelengths of 3.6 cm and 1.2 mm, respectively, searched for H2O and CH3OH
maser emission and observed the CO 2-1 and several NH3 lines toward all sources
in our sample. Other molecular tracers were observed in a subsample. The
presented results indicate that a substantial fraction of our sample harbors
HMPOs in a pre-UCHII region phase, the earliest known stage in the high-mass
star formation process.Comment: 16 pages, 11 eps-figures. Astrophysical Journal, in pres
Molecular jets driven by high-mass protostars: a detailed study of the IRAS 20126+4104 jet
We present here an extensive analysis of the protostellar jet driven by IRAS
20126+4104, deriving the kinematical, dynamical, and physical conditions of the
H2 gas along the flow. The jet has been investigated by means of near-IR H2 and
[FeII] narrow-band imaging, high resolution spectroscopy of the 1-0S(1) line
(2.12 um), NIR (0.9-2.5 um) low resolution spectroscopy, along with ISO-SWS and
LWS spectra (from 2.4 to 200 um). The flow shows a complex morphology. In
addition to the large-scale jet precession presented in previous studies, we
detect a small-scale wiggling close to the source, that may indicate the
presence of a multiple system. The peak radial velocities of the H2 knots range
from -42 to -14 km s^-1 in the blue lobe, and from -8 to 47 km s^-1 in the red
lobe. The low resolution spectra are rich in H_2 emission, and relatively faint
[FeII] (NIR), [OI] and [CII] (FIR) emission is observed in the region close to
the source. A warm H2 gas component has an average excitation temperature that
ranges between 2000 K and 2500 K. Additionally, the ISO-SWS spectrum reveals
the presence of a cold component (520 K), that strongly contributes to the
radiative cooling of the flow and plays a major role in the dynamics of the
flow. The estimated L(H2) of the jet is 8.2+/-0.7 L_sun, suggesting that
IRAS20126+4104 has an accretion rate significantly increased compared to
low-mass YSOs. This is also supported by the derived mass flux rate from the H2
lines (Mflux(H2)~7.5x10^-4 M_sun yr^-1). The comparison between the H2 and the
outflow parameters strongly indicates that the jet is driving, at least
partially, the outflow. As already found for low-mass protostellar jets, the
measured H2 outflow luminosity is tightly related to the source bolometric
luminosity.Comment: 16 pages, 12 figures. A&A accepte
Water abundances in high-mass protostellar envelopes: Herschel observations with HIFI
We derive the dense core structure and the water abundance in four massive
star-forming regions which may help understand the earliest stages of massive
star formation. We present Herschel-HIFI observations of the para-H2O 1_11-0_00
and 2_02-1_11 and the para-H2-18O 1_11-0_00 transitions. The envelope
contribution to the line profiles is separated from contributions by outflows
and foreground clouds. The envelope contribution is modelled using Monte-Carlo
radiative transfer codes for dust and molecular lines (MC3D and RATRAN), with
the water abundance and the turbulent velocity width as free parameters. While
the outflows are mostly seen in emission in high-J lines, envelopes are seen in
absorption in ground-state lines, which are almost saturated. The derived water
abundances range from 5E-10 to 4E-8 in the outer envelopes. We detect cold
clouds surrounding the protostar envelope, thanks to the very high quality of
the Herschel-HIFI data and the unique ability of water to probe them. Several
foreground clouds are also detected along the line of sight. The low H2O
abundances in massive dense cores are in accordance with the expectation that
high densities and low temperatures lead to freeze-out of water on dust grains.
The spread in abundance values is not clearly linked to physical properties of
the sources.Comment: 8 pages, 5 figures, accepted for publication the 15/07/2010 by
Astronomy&Astrophysics as a letter in the Herschel-HIFI special issu
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