83 research outputs found
Narrow band photometry of selected asteroids
The CCD photometry of selected asteroids was carried out to check for possible cometary activity in them. To distinguish the asteroids with possible cometary activity from those of the main belt, each object of interest was observed in two filters; one centered on the C2 emission band at 5140A (90A bandpass) and the other centered on the nearby continuum at 4845A (65A bandpass). None of the observed asteroids appear to have any C2 emission
Early observations of the Afterglow of GRB000301c
We report multiband observations of the Optical Transient (OT) associated
with GRB000301c carried out between 2--4 March 2000 using the 2.34-m Vainu
Bappu Telescope (VBT) at Kavalur, India. When combined with other reported
data, the initial decline in the R-band magnitude with log (), the time
since the burst is fit with a slope = -0.70 0.07 which
steepens after about 6.0 days to a slope of = -2.44 0.29.
This change in slope does not occur smoothly but there is an indication for a
bimodal distribution. The available measurements of the evolution of (B--R)
color do not show any discernible evolution in the first 12 days.Comment: 14 pages, 2 postscript figures, Accepted for Publication in ApJ
Letter
On the Clustering of GRBs on the Sky
The two-point correlation of the 4th (current) BATSE catalog (2494 objects)
is calculated. It is shown to be consistent with zero at nearly all angular
scales of interest. Assuming that GRBs trace the large scale structure in the
universe we calculate the angular correlation function for the standard CDM
(sCDM) model. It is shown to be at if the
BATSE catalog is assumed to be a volume-limited sample up to .
Combined with the error analysis on the BATSE catalog this suggests that nearly
GRBs will be needed to make a positive detection of the two-point
angular correlation function at this angular scale.Comment: 5 pages, Latex with aipproc.sty, incl. 1 ps-Fig., Proc. of the 5th
Huntsville Gamma Ray Burst Symposium, Oct. 1999, ed. R.M. Kippen, AI
Luminosity Function of GRBs
We attempt to constrain the luminosity function of Gamma Ray Bursts (GRBs) from the observed number count--flux relation and the afterglow redshift data. We assume three classes of luminosity functions for our analysis: (a) Log-normal distribution, (b) Schechter distribution, and (c) Scale-free distribution. We assume several models of the evolution of the GRB population for each luminosity function. Our analysis shows that: (a) log-normal is the only luminosity function that is compatible with both the observations. This result is independent of the GRB evolution model, (b) for log-normal function, the average photon luminosity and the width of the luminosity function that are compatible with both the observations fall in the range: 10^{55} sec^{-1} \la L_0 \la 10^{56} sec^{-1} and 2 \la \sigma \la 3, (c) the agreement of observations with other luminosity functions requires the GRB population to evolve more strongly than the evolution of the star-formation rate of the universe
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
RECENT PROGRESS OF DENDRIMERS IN DRUG DELIVERY FOR CANCER THERAPY
With the recent advances of nanotechnology, dendrimers are emerging as a highly attractive class of drug delivery vectors for cancer therapy. Dendrimers are multifunctional smart Nanocarriers to deliver one or more therapeutic agent safely and selectively to cancer cells. The high level of control over the synthesis of dendritic architecture makes dendrimers a nearly perfect (spherical) nanocarrier for site-specific drug delivery. The presence of functional groups in the dendrimers exterior also permits the addition of other moieties that can actively target certain diseases which are now widely used as tumor targeting strategies. Drug encapsulation, solubilization and passive targeting also equally contribute to the therapeutic use of dendrimers. Dendrimers are ideal carrier vehicles on cytotoxicity, blood plasma retention time, biodistribution and tumor uptake. In this review we highlight the advantages of dendrimers over conventional chemotherapy, toxicity and its management, following anti-cancer drugs delivered by using dendrimers and recent advances in drug delivery by various types of dendrimers as well as its diagnostic applications
Searching for GRB remnants in nearby galaxies
Gamma Ray Bursts (GRBs) are expected to leave behind GRB remnants, similar to
how ``standard'' supernovae (SN) leave behind SN remnants. The identification
of these remnants in our own and in nearby galaxies would allow a much closer
look at GRB birth sites, and possibly lead to the discovery of the compact
object left behind. It would also provide independent constraints on GRB rates
and energetics. We have initiated an observational program to search for GRB
remnants in nearby galaxies. The identification is based on specific line
ratios, such as OIII/ and HeII/, which are expected to be
unusually high in case of GRB remnants according to the theoretical predictions
of Perna et al. (2000). The observing strategies and preliminary studies from a
test run at 2.34 m VBT as well as archival data from planetary nebulae surveys
of spiral galaxies are discussed.Comment: 4 pages, uses aipproc.cls To appear in AIP, proceeding of GRB
conference '30 years after the discovery' held at Santa Fe, NM from 8-12
Sept, 200
Impact of mothers’ knowledge and support for sustaining exclusive breastfeeding
Background: Breast milk is the best milk for the baby. It is beneficial for the baby as well as the mother, family, and nation. In spite of an established fact, still, a very low percentage (44.2%) is implementing it. Objective: The objective of this study was to find out the knowledge, concerns, and difficulties in breastfeeding and the obstacles in the practicing breastfeeding. Materials and Methods: A cross-sectional study was done at pediatric clinics in Warangal. A total of 1010 lactating mothers who were presenting for regular check-ups were enrolled. After taking oral consent, mothers were interviewed through a predesigned questionnaire containing 50 questions on pre- and post-natal counseling received, and knowledge of exclusive breastfeeding, importance of skin-to-skin contact (SSC), and their educational status and hygiene. The entire session of interview was carried out in the optimum privacy to create a favorable environment of acquiring the data. Results: Of 1010 mothers enrolled, only 25.4% had received antenatal counseling, 15.8% had received postnatal counseling regarding exclusive breastfeeding, 56.4% followed exclusive breastfeeding (EBF), and SSC was maintained by only 2%, after delivery which played an important role in breastfeeding, p=0.000003 for antenatal counseling and EBF. Conclusion: More attention should be given in educating mothers when they conceive, regarding breastfeeding, its problems and skills, during their first visit to health-care professionals
Structural Instability in Polyacene : A Projector Quantum Monte Carlo Study
We have studied polyacene within the Hubbard model to explore the effect of
electron correlations on the Peierls' instability in a system marginally away
from one-dimension. We employ the projector quantum Monte Carlo method to
obtain ground state estimates of the energy and various correlation functions.
We find strong similarities between polyacene and polyacetylene which can be
rationalized from the real-space valence-bond arguments of Mazumdar and Dixit.
Electron correlations tend to enhance the Peierls' instability in polyacene.
This enhancement appears to attain a maximum at and the maximum
shifts to larger values when the alternation parameter is increased. The system
shows no tendency to destroy the imposed bond-alternation pattern, as evidenced
by the bond-bond correlations. The cis- distortion is seen to be favoured over
the trans- distortion. The spin-spin correlations show that undistorted
polyacene is susceptible to a SDW distortion for large interaction strength.
The charge-charge correlations indicate the absence of a CDW distortion for the
parameters studied.Comment: 13 pages, 10 figures available on reques
CD imaging of gamma ray burster fields
Gamma Ray Bursts (GRBs) have been known for almost three decades. The nature of the objects producing these bursts is yet unknown and no counterparts have been identified in any other wavelength band so far except for GB970228 recently. In an attempt to identify the optical counterparts of GRBs we obtain deep CCD images of selected, strong GRB fields through broad band filters. From these images we expect to be able to identify any peculiar objects on the basis of photometric colours andlor variability. In this paper we present the preliminary results of the data obtained during our observing run in November 1996 at the UP State Observatory, Nainital
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