52 research outputs found
The fly's eye project: Sidereal tracking on a hexapod mount
The driving objective of the Fly's Eye Project is a high resolution, high coverage time-domain survey in multiple optical passbands: our goal is to cover the entire visible sky above the 30° horizontal altitude with a cadence of ~ 3 min. Imaging is intended to perform with 19 wide-field cameras mounted on a hexapod platform. The essence of the hexapod allows us to build an instrument that does not require any kind of precise alignment and, in addition, the similar mechanics can be involved independently of the geographical location of the device. Here we summarize our early results with a single camera, focusing on the sidereal tracking as it is performed with the hexapod built by our group
HAT-P-13: a multi-site campaign to detect the transit of the second planet in the system
A possible transit of HAT-P-13c has been predicted to occur on 2010 April 28.
Here we report on the results of a multi-site campaign that has been organised
to detect the event. CCD photometric observations have been carried out at five
observatories in five countries. We reached 30% time coverage in a 5 days
interval centered on the suspected transit of HAT-P-13c. Two transits of
HAT-P-13b were also observed. No transit of HAT-P-13c has been detected while
the campaign was on. By a numerical experiment with 10^5 model systems we
conclude that HAT-P-13c is not a transiting exoplanet with a significance level
from 65% to 72%, depending on the planet parameters and the prior assumptions.
We present two times of transit of HAT-P-13b ocurring at BJD 2455141.5522 +-
0.0010 and BJD 2455249.4508 +- 0.0020. The TTV of HAT-P-13b is consistent with
zero within 0.001 days. The refined orbital period of HAT-P-13b is 2.916293 +-
0.000010 days.Comment: 5 pages, 4 figures, to be accepted by A&
Image-based Classification of Variable Stars: First Results from Optical Gravitational Lensing Experiment Data
Recently, machine learning methods presented a viable solution for automated
classification of image-based data in various research fields and business
applications. Scientists require a fast and reliable solution to be able to
handle the always growing enormous amount of data in astronomy. However, so far
astronomers have been mainly classifying variable star light curves based on
various pre-computed statistics and light curve parameters. In this work we use
an image-based Convolutional Neural Network to classify the different types of
variable stars. We used images of phase-folded light curves from the OGLE-III
survey for training, validating and testing and used OGLE-IV survey as an
independent data set for testing. After the training phase, our neural network
was able to classify the different types between 80 and 99%, and 77-98%
accuracy for OGLE-III and OGLE-IV, respectively.Comment: Accepted in ApJL, 11pages, 5 figures, 8 table
Antimycobacterial activity of peptide conjugate of pyridopyrimidine derivative against Mycobacterium tuberculosis in a series of in vitro and in vivo models
New pyridopyrimidine derivatives were defined using a novel HTS in silico docking method
(FRIGATE). The target protein was a dUTPase enzyme (EC 3.6.1.23; Rv2697) which plays a key
role in nucleotide biosynthesis of Mycobacterium tuberculosis (Mtb). Top hit molecules were
assayed in vitro for their antimycobacterial effect on Mtb H37Rv culture. In order to enhance the
cellular uptake rate, the TB820 compound was conjugated to a peptid-based carrier and a
nanoparticle type delivery system (polylactide-co-glycolide, PLGA) was applied. The conjugate had
relevant in vitro antitubercular activity with low in vitro and in vivo toxicity. In a Mtb H37Rv
infected guinea pig model the in vivo efficacy of orally administrated PLGA encapsulated
compound was proved: animals maintained a constant weight gain and no external clinical signs of
tuberculosis were observed. All tissue homogenates from lung, liver and kidney were found
negative for Mtb, and diagnostic autopsy showed that no significant malformations on the tissues
occurred
On the selection and design of proteins and peptide derivatives for the production of photoluminescent, red-emitting gold quantum clusters
Novel pathways of the synthesis of photoluminescent gold quantum clusters (AuQCs) using biomolecules as reactants provide biocompatible products for biological imaging techniques. In order to rationalize the rules for the preparation of red-emitting AuQCs in aqueous phase using proteins or peptides, the role of different organic structural units was investigated. Three systems were studied: proteins, peptides, and amino acid mixtures, respectively. We have found that cysteine and tyrosine are indispensable residues. The SH/S-S ratio in a single molecule is not a critical factor in the synthesis, but on the other hand, the stoichiometry of cysteine residues and the gold precursor is crucial. These observations indicate the importance of proper chemical behavior of all species in a wide size range extending from the atomic distances (in the AuI-S semi ring) to nanometer distances covering the larger sizes of proteins assuring the hierarchical structure of the whole self-assembled system
The rise and fall of a binary AGN candidate: the story of PSO J334.2028+1.4075
Apparently periodic optical variations of the luminous high-redshift (z=2.06)
quasar PSO J334.2028+1.4075 led Liu et al. (2015) to interpret the variability
as the orbital period of a binary supermassive black hole (SMBH) residing in a
single circumbinary accretion disk. The proposed orbital separation was around
0.006 pc, and the possible inspiral time about 7 yr in the rest frame of the
quasar. Such objects would be of high interest as the difficult-to-find end
products of binary SMBH evolution, and potential sources of low-frequency
gravitational waves. However, extending the time baseline of the variability
study, Liu et al. (2016) later found that the periodicity of PSO
J334.2028+1.4075 does not remain persistent. Foord et al. (2017) did not find
evidence for the binary active galactic nucleus scenario based on Chandra X-ray
observations. The object has also been studied in detail in the radio (Mooley
et al. 2018) with the Karl G. Jansky Very Large Array (VLA) and the Very Long
Baseline Array (VLBA), revealing a lobe-dominated quasar at kpc scales, and
possibly a precessing jet, which might retain PSO J334.2028+1.4075 as a binary
SMBH candidate. Here we report on our 1.7-GHz observation with the European
VLBI Network (EVN) which complements the VLBA data taken at higher frequencies,
and discuss the current knowledge about the nature of this interesting object.Comment: 4 pages, 1 figure, accepted for the proceedings of the 14th European
VLBI Network Symposium & Users Meeting (Granada, Spain, 8-11 Oct 2018).
Proceedings of Science, PoS(EVN2018)09
An additive manufactured CubeSat mirror incorporating a novel circular lattice
Additive Manufacturing (AM; 3D printing) for mirror fabrication allows for intricate designs that can combine lightweight structures and integrated mounting. Conventional lightweight structures utilise cubic or prismatic unit cells, which do not provide uniform support at the edge of curved mirrors. We present a new circular lattice based upon cylindrical coordinates and how this lattice has been incorporated within an 80 mm diameter mirror intended for use in a 3U CubeSat telescope. Several design iterations are explored, which include prototype mirrors produced in a titanium alloy and a finite element analysis of the one of the design iterations
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