168 research outputs found
A Spitzer Study of the Mass Loss Histories of Three Bipolar Pre-Planetary Nebulae
We present the results of far-infrared imaging of extended regions around
three bipolar pre-planetary nebulae, AFGL 2688, OH 231.8+4.2, and IRAS
163423814, at 70 and 160 m with the MIPS instrument on the Spitzer
Space Telescope. After a careful subtraction of the point spread function of
the central star from these images, we place constraints on the existence of
extended shells and thus on the mass outflow rates as a function of radial
distance from these stars. We find no apparent extended emission in AFGL 2688
and OH 231.8+4.2 beyond 100 arcseconds from the central source. In the case of
AFGL 2688, this result is inconsistent with a previous report of two extended
dust shells made on the basis of ISO observations. We derive an upper limit of
M yr and M
yr for the dust mass loss rate of AFGL 2688 and OH 231.8, respectively,
at 200 arcseconds from each source. In contrast to these two sources, IRAS
163423814 does show extended emission at both wavelengths, which can be
interpreted as a very large dust shell with a radius of 400 arcseconds
and a thickness of 100 arcseconds, corresponding to 4 pc and 1 pc,
respectively, at a distance of 2 kpc. However, this enhanced emission may also
be galactic cirrus; better azimuthal coverage is necessary for confirmation of
a shell. If the extended emission is a shell, it can be modeled as enhanced
mass outflow at a dust mass outflow rate of M
yr superimposed on a steady outflow with a dust mass outflow rate of
M yr. It is likely that this shell has swept
up a substantial mass of interstellar gas during its expansion, so these
estimates are upper limits to the stellar mass loss rate.Comment: 31 pages, 12 figures, accepted to A
X-ray emission from Planetary Nebulae. I. Spherically symmetric numerical simulations
(abridged) The interaction of a fast wind with a spherical Asymptotic Giant
Branch (AGB) wind is thought to be the basic mechanism for shaping
Pre-Planetary Nebulae (PPN) and later Planetary Nebulae (PN). Due to the large
speed of the fast wind, one expects extended X-ray emission from these objects,
but X-ray emission has only been detected in a small fraction of PNs and only
in one PPN. Using numerical simulations we investigate the constraints that can
be set on the physical properties of the fast wind (speed, mass-flux, opening
angle) in order to produce the observed X-ray emission properties of PPNs and
PNs. We combine numerical hydrodynamical simulations including radiative
cooling using the code FLASH with calculations of the X-ray properties of the
resulting expanding hot bubble using the atomic database ATOMDB. In this first
study, we compute X-ray fluxes and spectra using one-dimensional models.
Comparing our results with analytical solutions, we find some agreements and
many disagreements. In particular, we test the effect of different time
histories of the fast wind on the X-ray emission and find that it is determined
by the final stage of the time history during which the fast wind velocity has
its largest value. The disagreements which are both qualitative and
quantitative in nature argue for the necessity of using numerical simulations
for understanding the X-ray properties of PNs.Comment: 17 pages, accepted for publication in ApJ (July 27, 2006), uses
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High-Resolution Near-Infrared Imaging and Polarimetry of Four Proto-Planetary Nebulae
High-resolution near-infrared HST NICMOS (F160W, F222M) images and
polarization (2 um) observations were made of four bipolar proto-planetary
nebulae (PPNs): IRAS 17150-3224, IRAS 17441-2411, IRAS 17245-3951, and IRAS
16594-4656. The first three of these are viewed nearly edge-on, and for the
first time the central stars in them are seen. Color maps reveal a reddened
torus between the bipolar lobes in the edge-on cases, with bluer lobes. The
polarization values are high, with maximum values ranging from 40 to 80%. The
polarization patterns are basically centrosymmetric, with some deviations in
the low polarization equatorial regions. For IRAS 17150-3224, circumstellar
arcs are seen at 1.6 um, along with a newly-discovered loop in the equatorial
region. Bright caps are seen at the end of the lobes, indicating that they are
not open-ended. A distinct point-symmetric pattern is seen in the strengths of
the polarization vectors, especially in IRAS 17150-3224. HST NICMOS
observations provide a valuable complement to the WFPC2 visible images in
deriving the basic structure of bipolar PPNs.Comment: 20 pages, 12 figures, accepted for publication in Astronomical
Journal higher resolution figures are available on
http://katherine.as.arizona.edu/~ksu/cv/su_nicmos7840.ps.g
Innovation of System Biological Approach in Computational Drug Discovery
Computational methods like classification and network-based algorithms can be used to understand the mode of action and the efficacy of a given compound and to help elucidating the patho-physiology of a disease. In the pharmacological industry there has already been a shift from symptomatic oriented drugs that can relieve the symptoms but not the cause of the disease to pathology-based drugs whose targets are the genes and proteins involved in the etiology of the disease. Drugs targeting the affected pathway have thus the potential to become therapeutic. A network approach to drug design would examine the effect of drugs in the context of a network of relevant protein regulatory metabolic interactions resulting in the development of a drug that would hit multiple targets selected in such a way as to decrease network integrity and so completely disrupt the functioning of the network. The screening of a compound to quickly identify the proteins it interacts with gives us all the necessary tools to identify and repair the deregulated biological pathway causing the disease
Modulation of Cyclic AMP Levels in Fallopian Tube Cells by Natural and Environmental Estrogens
Autocrine/paracrine factors generated in response to 17β-estradiol (E2) within the fallopian tube (FT) facilitate fertilization and early embryo development for implantation. Since cyclic AMP (cAMP) plays a key role in reproduction, regulation of its synthesis by E2 may be of biological/pathophysiological relevance. Herein, we investigated whether cAMP production in FT cells (FTCs) is regulated by E2 and environmental estrogens (EE’s; xenoestrogens and phytoestrogens). Under basal conditions, low levels of extracellular cAMP were detectable in bovine FTCs (epithelial cells and fibroblasts; 1:1 ratio). Treatment of FTCs with forskolin (AC; adenylyl cyclase activator), isoproterenol (β-adrenoceptor agonist) and IBMX (phosphodiesterase (PDE) inhibitor) dramatically (>10 fold) increased cAMP; whereas LRE1 (sAC; soluble AC inhibitor) and 2’,5’-dideoxyadenosine (DDA; transmembrane AC (tmAC)) inhibitor decreased cAMP. Comparable changes in basal and stimulated intracellular cAMP were also observed. Ro-20-1724 (PDE-IV inhibitor), but not milrinone (PDE-III inhibitor) nor mmIBMX (PDE-I inhibitor), augmented forskolin-stimulated cAMP levels, suggesting that PDE-IV dominates in FTCs. E2 increased cAMP levels and CREB phosphorylation in FTCs, and these effects were mimicked by EE’s (genistein, 4-hydroxy-2’,4’,6’-trichlorobiphenyl, 4-hydroxy-2’,4’,6’-dichlorobiphenyl). Moreover, the effects of E2 and EE were blocked by the tmAC inhibitor DDA, but not by the ERα/β antagonist ICI182780. Moreover, BAPTA-AM (intracellular-Ca2+ chelator) abrogated the effects of E2, but not genistein, on cAMP suggesting differential involvement of Ca2+. Treatment with non-permeable E2-BSA induced cAMP levels and CREB-phosphorylation; moreover, the stimulatory effects of E2 and EEs on cAMP were blocked by G15, a G protein-coupled estrogen receptor (GPER) antagonist. E2 and IBMX induced cAMP formation was inhibited by LRE1 and DDA suggesting involvement of both tmAC and sAC. Our results provide the first evidence that in FTCs, E2 and EE’s stimulate cAMP synthesis via GPER. Exposure of the FT to EE’s and PDE inhibitors may result in abnormal non-cyclic induction of cAMP levels which may induce deleterious effects on reproduction
Urbanisation and new agroecologies : the story of Bengaluru’s peripheries
Rural–urban interfaces worldwide are increasingly
witnessing massive transformations in the structure,
functions, and services of complex ecosystems of these
zones. An attempt has been made to understand the
transitions triggered by urbanisation in the peri-urban
agricultural systems of Bengaluru. Using a combination
of land-use change analysis and group interactions, the
temporal and spatial patterns in the impacts of urban
expansion on agroecology in Bengaluru’s peripheries
have been traced. The varying nature of agroecological
and sociocultural impacts corresponding to differences
in the pattern of urban expansion along different
directions from the city have also been unravelled.
Further, agroecological repercussions of existing and
proposed urban planning strategies for Bengaluru have
been discussed
DOCKING STUDIES OF AMINOHYDANTOIN DERIVATIVES AS ANTIMALARIAL AGENTS
Objective: Docking studies of aminohydantoin derivatives as antimalarial agents. A novel derivative of aminohydantoins was selected from the literature. Method: in-silco studies using docking methodology. The compounds were sketched and energy minimized using Chem draw ultra and Chem 3D ultra respectively. Further, the compounds were docked into Plasmodium falciparum transferase inhibitor (3L7) using Molegro Virtual Platform. Twenty eight compounds were docked into the active site of Pf-lactate dehydrogenase cavity and all of them found to have similar binding interactions of a co-crystalized ligand. Result: The compounds were showed good docking score like moldock score and re-rank score. The finding of docking studies shows a typical molecular interaction pattern with lactate dehydrogenase. The binding interaction information derived from these molecules will be useful in future antimalarial agent design. Conclusion: From the docking study, it was observed that ligands bind to the electrostatic, hydrophobic clamp formed by the residues Asp 76(B), Tyr 190(B), Tyr 80(B) and Lys 72(B) which play an important role for Plasmodium falciparum inhibition. The binding affinity, grid calculation and RMSD percentage lower and upper parameters were calculated. Hence, the observable data indicated that, above compounds can serve as good leads for further modification and optimization in the of treatment malaria.
Keywords: Molegro, Chemdraw, aminohydantoins and docking, studies as Plasmodium falciparum, 4RAO, moldock score
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