4,976 research outputs found
Planetary Nebulae with UVIT II: Revelations from FUV vision of Butterfly Nebula NGC 6302
The high excitation planetary nebula, NGC 6302, has been imaged in two
far-ultraviolet (FUV) filters, F169M (Sapphire; {\lambda}: 1608
{\AA}) and F172M (Silica; {\lambda}: 1717 {\AA}) and two NUV
filters, N219M (B15; {\lambda}: 2196 {\AA}) and N279N (N2;
{\lambda}: 2792 {\AA}) with the Ultra Violet Imaging Telescope
(UVIT). The FUV F169M image shows faint emission lobes that extend to about 5
arcmin on either side of the central source. Faint orthogonal collimated
jet-like structures are present on either side of the FUV lobes through the
central source. These structures are not present in the two NUV filters nor in
the FUV F172M filter. Optical and IR images of NGC 6302 show bright emission
bipolar lobes in the east-west direction with a massive torus of molecular gas
and dust seen as a dark lane in the north-south direction. The FUV lobes are
much more extended and oriented at a position angle of 113{\deg}. They and the
jet-like structures might be remnants of an earlier evolutionary phase, prior
to the dramatic explosive event that triggered the Hubble type bipolar flows
approximately 2200 years ago. The source of the FUV lobe and jet emission is
not known, but is likely due to fluorescent emission from H molecules. The
cause of the difference in orientation of optical and FUV lobes is not clear
and, we speculate, could be related to two binary interactions.Comment: 9 pages, 5 figures, accepted for publication in Astronomy &
Astrophysic
Multiband Comparative Study of Optical Microvariability in RL vs. RQ Quasars
We present the results of an optical multi-band (BVR) photometric monitoring
program of 22 core-dominated radio-loud quasars (CRLQs) and 22 radio-quiet
quasars (RQQs). The aim was to compare the properties of microvariability in
both types of quasars. We detected optical microvariability in 5 RQQs and 4
CRLQs. Our results confirm that microvariability in RQQs may be as frequent as
in CRLQs. In addition we compare microvariability duty cycles in different
bands. Finally, the implications for the origin of the microvariations are
briefly discussed.Comment: 17 pages, 14 figures, Accepted for publication in the Astronomical
Journa
Drug screening using shape-based virtual screening and in vitro experimental models of cutaneous Leishmaniasis
Cutaneous leishmaniasis (CL) is one of the most disregarded tropical neglected disease with the occurrence of self-limiting ulcers and triggering mucosal damage and stigmatizing scars, leading to huge public health problems and social negative impacts. Pentavalent antimonials are the first-line drug for CL treatment for over 70 years and present several drawbacks in terms of safety and efficacy. Thus, there is an urgent need to search for non-invasive, non-toxic and potent drug candidates for CL. In this sense, we have implemented a shape-based virtual screening approach and identified a set of 32 hit compounds. In vitro phenotypic screenings were conducted using these hit compounds to check their potential leishmanicidal effect towards Leishmania amazonensis (L. amazonensis). Two (Cp1 and Cp2) out of the 32 compounds revealed promising antiparasitic activities, exhibiting considerable potency against intracellular amastigotes present in peritoneal macrophages (IC₅₀ values of 9.35 and 7.25 μm, respectively). Also, a sterile cidality profile was reached at 20 μm after 48 h of incubation, besides a reasonable selectivity (≈8), quite similarly to pentamidine, a diamidine still in use clinically for leishmaniasis. Cp1 with an oxazolo[4,5-b]pyridine scaffold and Cp2 with benzimidazole scaffold could be developed by lead optimization studies to enhance their leishmanicidal potency
A matter of taste: the adverse effect of pollen compounds on the pre-ingestive gustatory experience of sugar solutions for honeybees
This is the final version. Available from the publisher via the DOI in this record.The online version of this
article (https://doi.org/10.1007/s00359-019-01347-z) contains
supplementary material, which is available to authorized users.In addition to sugars, nectar contains multiple nutrient compounds in varying concentrations yet little is known of their effect on the reward properties of nectar and the resulting implications for insect behaviour. We examined the pre-ingestive responses of honeybees to sucrose solutions containing a mix of pollen compounds, the amino acids proline or phenylalanine, or known distasteful substances, quinine and salt. We predicted that in taste and learning assays, bees would respond positively to the presence of nutrient compounds in a sucrose solution. However, bees’ proboscis extension responses decreased when their antennae were stimulated with pollen- or amino-acid supplemented sucrose solutions. Compared to pure sucrose, bees exhibited worse acquisition when conditioned to an odour with pollen-supplemented sucrose as the unconditioned stimulus. Such learning impairment was also observed with quinine-containing sucrose solutions. Our results suggest that bees can use their antennae to detect pollen compounds in floral nectars. Depending on the type and concentrations of compounds present, this may result in nectar being perceived as distasteful by bees, making it less effective in reinforcing the learning of floral cues. Such reward devaluation might be adaptive in cases where plants benefit from regulating the frequency of bee visitation.UKIERI (British Council)Biotechnology and Biological Sciences Research Council (BBSRC) (SWBiosciences DTP
Multifractal Behaviour of n-Simplex Lattice
We study the asymptotic behaviour of resistance scaling and fluctuation of
resistance that give rise to flicker noise in an {\em n}-simplex lattice. We
propose a simple method to calculate the resistance scaling and give a
closed-form formula to calculate the exponent, , associated with
resistance scaling, for any n. Using current cumulant method we calculate the
exact noise exponent for n-simplex lattices.Comment: Latex, 9 pages including one figur
Sequential Deliberation for Social Choice
In large scale collective decision making, social choice is a normative study
of how one ought to design a protocol for reaching consensus. However, in
instances where the underlying decision space is too large or complex for
ordinal voting, standard voting methods of social choice may be impractical.
How then can we design a mechanism - preferably decentralized, simple,
scalable, and not requiring any special knowledge of the decision space - to
reach consensus? We propose sequential deliberation as a natural solution to
this problem. In this iterative method, successive pairs of agents bargain over
the decision space using the previous decision as a disagreement alternative.
We describe the general method and analyze the quality of its outcome when the
space of preferences define a median graph. We show that sequential
deliberation finds a 1.208- approximation to the optimal social cost on such
graphs, coming very close to this value with only a small constant number of
agents sampled from the population. We also show lower bounds on simpler
classes of mechanisms to justify our design choices. We further show that
sequential deliberation is ex-post Pareto efficient and has truthful reporting
as an equilibrium of the induced extensive form game. We finally show that for
general metric spaces, the second moment of of the distribution of social cost
of the outcomes produced by sequential deliberation is also bounded
A survey of Low Luminosity Compact sources and its implication for evolution of radio-loud AGNs. I. Radio data
We present a new sample of Compact Steep Spectrum (CSS) sources with radio
luminosity below 10^26 W/Hz at 1.4 GHz called the low luminosity compact (LLC)
objects. The sources have been selected from FIRST survey and observed with
MERLIN at L-band and C-band. The main criterion used for selection was
luminosity of the objects and approximately one third of the CSS sources from
the new sample have a value of radio luminosity comparable to FRIs. About 80%
of the sources have been resolved and about 30% of them have weak extended
emission and disturbed structures when compared with the observations of higher
luminosity CSS sources. We studied correlation between radio power and linear
size, and redshift with a larger sample that included also published samples of
compact objects and large scale FRIIs and FRIs. The low luminosity compact
objects occupy the space in radio power versus linear size diagram below the
main evolutionary path of radio objects. We suggest that many of them might be
short-lived objects, and their radio emission may be disrupted several times
before becoming FRIIs. We conclude that there exists a large population of
short-lived low luminosity compact objects unexplored so far and part of them
can be precursors of large scale FRIs.Comment: 19 pages, 5 figures, 3 tables, MNRAS in pres
Optical variability properties of high luminosity AGN classes
We present the results of a comparative study of the intra-night optical
variability (INOV) characteristics of radio-loud and radio-quiet quasars, which
involves a systematic intra-night optical monitoring of seven sets of high
luminosity AGNs covering the redshift range {\it z} to {\it z}
. The sample, matched in the optical luminosity -- redshift (M
-- z) plane, consists of seven radio-quiet quasars (RQQs), eight radio
lobe-dominated quasars (LDQs), six radio core-dominated quasars (CDQs) and five
BL Lac objects (BLs). Systematic CCD observations, aided by a careful data
analysis procedure, have allowed us to detect INOV with amplitudes as low as
1%. Present observations cover a total of 113 nights (720 hours) with only a
single quasar monitored as continuously as possible on a night. Considering
cases of only unambiguous detections of INOV we have estimated duty cycles
(DCs) of 17%, 12%, 20% and 72% respectively for RQQs, LDQs, CDQs, and BLs. The
low amplitude and low DC of INOV shown by RQQs compared to BLs can be
understood in terms of their having optical synchrotron jets which are modestly
misdirected from us. From our fairly extensive dataset, no unambiguous general
trend of a correlation between the INOV amplitude and the apparent optical
brightness of the quasar is noticed.Comment: 36 pages, 14 Figures, due to large size Fig. 5,6,11 and 12 are not
included. Intersted people contact to [email protected]. Submitted to
Journal of Astrophysics and Astronom
On the Populations of Radio Galaxies with Extended Morphology at z<0.3
Extended extragalactic radio sources have traditionally been classified into
FR I and II types, based on the ratio r of the separation S between the
brightest regions on either sides of the host galaxy and the total size T of
the radio source. Here we examine the distribution of various physical
properties as a function of r of 1040 luminous radio galaxies (RGs) at z<0.3
from the SDSS, NVSS, and FIRST. About 2/3 of the RGs are lobe-dominated (LD),
and 1/3 have prominent jets. If we follow the original definition of the FR
types (a division based solely on r), FR I and FR II RGs overlap in their host
galaxy properties. However, the rare, LD sources with r>0.8 AND OIII5007 line
luminosity >10^6 Lsun are markedly different on average from the rest of the
RGs, in the sense that they are hosted in lower mass galaxies, live in
relatively sparse environments, and have higher accretion rates onto the
central SMBH. Thus these objects and the rest of RGs form a well-defined
dichotomy. Motivated by the stark differences in the nuclear emission line
properties of the RG subsamples, we suggest that the accretion rate onto the
SMBH may play the primary role in creating the different morphologies. At
relatively high accretion rates, the accretion system may produce powerful jets
that create the "classical double" morphology (roughly corresponding to the LD
sources with r>0.8 and emission lines); at lower accretion rates the jets from
a radiatively inefficient accretion flow generate radio lobes without apparent
"hot spots" at the edge (corresponding to the majority of LD sources). At
slightly lower accretion rates AND in galaxies with dense galactic structure,
sources with prominent jets result. It is possible that while the high
accretion rate systems could affect sub-Mpc scale environments, the jets from
lower accretion rate systems may efficiently suppress activity within the host
galaxies.Comment: ApJ, accepted. 20 pages, 16 figures, 4 tables. Image quality of
Figures 1 & 2 degraded due to size limits. Table 4 is available and kept
up-to-date at http://member.ipmu.jp/yen-ting.lin/RG/index.html. Higher
resolution version available at
http://member.ipmu.jp/yen-ting.lin/Data/ytlin.pd
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