2,064 research outputs found
PONDER - A Real time software backend for pulsar and IPS observations at the Ooty Radio Telescope
This paper describes a new real-time versatile backend, the Pulsar Ooty Radio
Telescope New Digital Efficient Receiver (PONDER), which has been designed to
operate along with the legacy analog system of the Ooty Radio Telescope (ORT).
PONDER makes use of the current state of the art computing hardware, a
Graphical Processing Unit (GPU) and sufficiently large disk storage to support
high time resolution real-time data of pulsar observations, obtained by
coherent dedispersion over a bandpass of 16 MHz. Four different modes for
pulsar observations are implemented in PONDER to provide standard reduced data
products, such as time-stamped integrated profiles and dedispersed time series,
allowing faster avenues to scientific results for a variety of pulsar studies.
Additionally, PONDER also supports general modes of interplanetary
scintillation (IPS) measurements and very long baseline interferometry data
recording. The IPS mode yields a single polarisation correlated time series of
solar wind scintillation over a bandwidth of about four times larger (16 MHz)
than that of the legacy system as well as its fluctuation spectrum with high
temporal and frequency resolutions. The key point is that all the above modes
operate in real time. This paper presents the design aspects of PONDER and
outlines the design methodology for future similar backends. It also explains
the principal operations of PONDER, illustrates its capabilities for a variety
of pulsar and IPS observations and demonstrates its usefulness for a variety of
astrophysical studies using the high sensitivity of the ORT.Comment: 25 pages, 14 figures, Accepted by Experimental Astronom
Detection of long nulls in PSR B170616, a pulsar with large timing irregularities
Single pulse observations, characterizing in detail, the nulling behaviour of
PSR B170616 are being reported for the first time in this paper. Our regular
long duration monitoring of this pulsar reveals long nulls of 2 to 5 hours with
an overall nulling fraction of 312\%. The pulsar shows two distinct phases
of emission. It is usually in an active phase, characterized by pulsations
interspersed with shorter nulls, with a nulling fraction of about 15 \%, but it
also rarely switches to an inactive phase, consisting of long nulls. The nulls
in this pulsar are concurrent between 326.5 and 610 MHz. Profile mode changes
accompanied by changes in fluctuation properties are seen in this pulsar, which
switches from mode A before a null to mode B after the null. The distribution
of null durations in this pulsar is bimodal. With its occasional long nulls,
PSR B170616 joins the small group of intermediate nullers, which lie between
the classical nullers and the intermittent pulsars. Similar to other
intermediate nullers, PSR B170616 shows high timing noise, which could be
due to its rare long nulls if one assumes that the slowdown rate during such
nulls is different from that during the bursts.Comment: Accepted for publication in MNRA
Simultaneous multi-frequency single pulse observations of pulsars
We performed simultaneous observations at 326.5 MHz with the Ooty Radio
Telescope and at 326, 610 and 1308 MHz with the Giant Meterwave Radio Telescope
for a sample of 12 pulsars, where frequency dependent single pulse behaviour
was reported. The single pulse sequences were analysed with fluctuation
analysis, sensitive to both the average fluctuation properties (using longitude
resolved fluctuation spectrum and two-dimensional fluctuation spectrum) as well
as temporal changes in these (using sliding two-dimensional fluctuation
spectrum ) to establish concurrent changes in subpulse drifting over the
multiple frequencies employed. We report subpulse drifting in PSR J09345249
for the first time. We also report pulse nulling measurements in PSRs
J09345249, B1508+55, J18222256, B184519 and J19010906 for the first
time. Our measurements of subpulse drifting and pulse nulling for the rest of
the pulsars are consistent with previously reported values. Contrary to
previous belief, we find no evidence for a frequency dependent drift pattern in
PSR B2016+28 implied by non-simultaneous observations by Oster et al. (1977).
In PSRs B1237+25, J18222256, J19010906 and B204516, our longer and
more sensitive observations reveal multiple drift rates with distinct P3. We
increase the sample of pulsars showing concurrent nulling across multiple
frequencies by more than 100 percent, adding 4 more pulsars to this sample. Our
results confirm and further strengthen the understanding that the subpulse
drifting and pulse nulling are broadband consistent with previous studies
(Gajjar et al. 2014a; Rankin 1986; Weltevrede et al. 2007) and are closely tied
to physics of polar gap.Comment: 22 pages, 44 figures, Single pulse studies of pulsars, accepted by
A&
Scatter broadening measurements of 124 pulsars at 327 MHz
We present the measurements of scatter broadening time-scales ()
for 124 pulsars at 327 MHz, using the upgraded Ooty Radio Telescope (ORT).
These pulsars lie in the dispersion measure range of 37 503 pc cm
and declination () range of 57. New
estimates for 58 pulsars are presented, increasing the sample of
all such measurements by about 40% at 327 MHz. Using all available
measurements in the literature, we investigate the dependence of on
dispersion measure. Our measurements, together with previously reported values
for , affirm that the ionized interstellar medium upto 3 kpc is
consistent with Kolmogorov spectrum, while it deviates significantly beyond
this distance.Comment: 19 pages, 4 figures, accepted for publication in Ap
Detection of radio emission from the gamma-ray pulsar J1732-3131 at 327 MHz
Although originally discovered as a radio-quiet gamma-ray pulsar, J1732-3131
has exhibited intriguing detections at decameter wavelengths. We report an
extensive follow-up of the pulsar at 327 MHz with the Ooty radio telescope.
Using the previously observed radio characteristics, and with an effective
integration time of 60 hrs, we present a detection of the pulsar at a
confidence level of 99.82%. The 327 MHz mean flux density is estimated to be
0.5-0.8 mJy, which establishes the pulsar to be a steep spectrum source and one
of the least-luminous pulsars known to date. We also phase-aligned the radio
and gamma-ray profiles of the pulsar, and measured the phase-offset between the
main peaks in the two profiles to be 0.240.06. We discuss the observed
phase-offset in the context of various trends exhibited by the radio-loud
gamma-ray pulsar population, and suggest that the gamma-ray emission from
J1732-3131 is best explained by outer magnetosphere models. Details of our
analysis leading to the pulsar detection, and measurements of various
parameters and their implications relevant to the pulsar's emission mechanism
are presented.Comment: 8 pages, 6 figures; Accepted for publication in MNRA
A process for the preparation of nolignan 3- ethyl-2-methyl-3- (2",4",5"-trimethoxy) phenyl-1-(2',4',5'-trimethoxy) phenyl-1-propene
The present invention relates to a novel neolignan (Neolasa-I) 3-ethyl-2-methyl-3-(2", 4", 5"-
trimethoxy-phenyl-1-(2' ,4' ,5'-trimethoxy)Phenyl-(2' ,4',5'-Trimethoxy)phenyl-1- propene and
a process for the preparation of high purity, higher yield neolignan, a-asarone, 2,4,5-
trimethoxy-phenylpropionone from B-asarone or B-asarone rich acorus calamus oil
containing a and Y-asarone by hydrogenating and dimerizing by treatment with DDQ in
presence of an organic acid
A PROCESS FOR THE PREPARATION OF PHARMACOLOGICALLY ACTIVE ά-ASARONE FROM TOXIC β-ASARONE RICH ACORUS CALAMUS OIL"
The present invention relates to a process for the preparation of high purity and yield aasarone,
trans 2,4,5-trimethoxy cinnamaldehyde, 2,4,5-trimethoxy-phenyl propionone, from
p-asarone or P-asarone rich Acorus calamus oil containing a and y-asarone by
hydrogenating, followed by treatment with DDQ with or without solid support of silica gel or
alumina in dry organic solvent and a-asarone can also be obtained by treating the
hydrogenated product of P-asarone or P-asarone rich Acorus calamus with DDQ in an
aqueous organic solvent to obtain an intermediate 2,4,5-trimethoxy phenyl propionone,
which in turn is reduced with sodiumborohydride to obtain the corresponding 2,4,5-
trimethoxy-phenyl propanol and followed by final treatment with a dehydrating agen
Identification of Genomic Regions and Sources for Wheat Blast Resistance through GWAS in Indian Wheat Genotypes
Wheat blast (WB) is a devastating fungal disease that has recently spread to Bangladesh and poses a threat to the wheat production in India, which is the second-largest wheat producing country in the world. In this study, 350 Indian wheat genotypes were evaluated for WB resistance in 12 field experiments in three different locations, namely Jashore in Bangladesh and Quirusillas and Okinawa in Bolivia. Single nucleotide polymorphisms (SNPs) across the genome were obtained using DArTseq (R) technology, and 7554 filtered SNP markers were selected for a genome-wide association study (GWAS). All the three GWAS approaches used identified the 2NS translocation as the only major source of resistance, explaining up to 32% of the phenotypic variation. Additional marker-trait associations were located on chromosomes 2B, 3B, 4D, 5A and 7A, and the combined effect of three SNPs (2B_180938790, 7A_752501634 and 5A_618682953) showed better resistance, indicating their additive effects on WB resistance. Among the 298 bread wheat genotypes, 89 (29.9%) carried the 2NS translocation, the majority of which (60 genotypes) were CIMMYT introductions, and 29 were from India. The 2NS carriers with a grand mean WB index of 6.6 showed higher blast resistance compared to the non-2NS genotypes with a mean index of 46.5. Of the 52 durum wheats, only one genotype, HI 8819, had the 2NS translocation and was the most resistant, with a grand mean WB index of 0.93. Our study suggests that the 2NS translocation is the only major resistance source in the Indian wheat panel analysed and emphasizes the urgent need to identify novel non-2NS resistance sources and genomic regions
Marker-assisted improvement of grain protein content and grain weight in Indian bread wheat
The leading Indian wheat cultivar ‘HUW234’ produces grain with relatively low protein content (GPC) and thousand grain weight (TGW). Therefore, marker-assisted backcrossing was used to improve these two important traits by introducing favorable genes/alleles from cv. ‘Glu133’, which harbors both alleles for both GPC (Gpc-B1) and TGW. Foreground selection for GPC was achieved using microsatellite markers Xucw108 linked with Gpc-B1 and Xgwm297 linked with TGW. Background selection applied to support recovery of the recurrent parent genotype was based on 86 genomically distributed microsatellites. A selected BC2F1 plant was the progenitor of 15 BC2F4 families, in which representation of the cv. HUW234 genome ranged from 89.5 to 93.0 %. The new derivatives of HUW234 were comparable in yield to the original cultivar, but with both significantly higher GPC and heavier kernels
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