25 research outputs found
A LOFAR radio search for single and periodic pulses from M31
Bright, short radio bursts are emitted by sources at a large range of
distances: from the nearby Crab pulsar to remote Fast Radio Bursts (FRBs). FRBs
are likely to originate from distant neutron stars, but our knowledge of the
radio pulsar population has been limited to the Galaxy and the Magellanic
Clouds. In an attempt to increase our understanding of extragalactic pulsar
populations, and its giant-pulse emission, we employed the low-frequency radio
telescope LOFAR to search the Andromeda Galaxy (M31) for radio bursts emitted
by young, Crab-like pulsars. For direct comparison we also present a LOFAR
study on the low-frequency giant pulses from the Crab pulsar; their fluence
distribution follows a power law with slope 3.04(3). A number of candidate
signals were detected from M31 but none proved persistent. FRBs are sometimes
thought of as Crab-like pulsars with exceedingly bright giant pulses -- given
our sensitivity, we can rule out that M31 hosts pulsars more than an order of
magnitude brighter than the Crab pulsar, assuming their pulse scattering
follows that of the known FRBs.Comment: Accepted for publication in A&A. 6 pages with 4 nice figure
Reconstructing the evolution of the mitochondrial ribosomal proteome
For production of proteins that are encoded by the mitochondrial genome, mitochondria rely on their own mitochondrial translation system, with the mitoribosome as its central component. Using extensive homology searches, we have reconstructed the evolutionary history of the mitoribosomal proteome that is encoded by a diverse subset of eukaryotic genomes, revealing an ancestral ribosome of alpha-proteobacterial descent that more than doubled its protein content in most eukaryotic lineages. We observe large variations in the protein content of mitoribosomes between different eukaryotes, with mammalian mitoribosomes sharing only 74 and 43% of its proteins with yeast and Leishmania mitoribosomes, respectively. We detected many previously unidentified mitochondrial ribosomal proteins (MRPs) and found that several have increased in size compared to their bacterial ancestral counterparts by addition of functional domains. Several new MRPs have originated via duplication of existing MRPs as well as by recruitment from outside of the mitoribosomal proteome. Using sensitive profileâprofile homology searches, we found hitherto undetected homology between bacterial and eukaryotic ribosomal proteins, as well as between fungal and mammalian ribosomal proteins, detecting two novel human MRPs. These newly detected MRPs constitute, along with evolutionary conserved MRPs, excellent new screening targets for human patients with unresolved mitochondrial oxidative phosphorylation disorders
Correction:How the COVID-19 pandemic highlights the necessity of animal research (vol 30, pg R1014, 2020)
(Current Biology 30, R1014âR1018; September 21, 2020) As a result of an author oversight in the originally published version of this article, a number of errors were introduced in the author list and affiliations. First, the middle initials were omitted from the names of several authors. Second, the surname of Dr. van Dam was mistakenly written as âDam.â Third, the first name of author Bernhard Englitz was misspelled as âBernardâ and the surname of author B.J.A. Pollux was misspelled as âPullox.â Finally, Dr. Keijer's first name was abbreviated rather than written in full. These errors, as well as various errors in the author affiliations, have now been corrected online
The LOFAR pilot surveys for pulsars and fast radio transients
We have conducted two pilot surveys for radio pulsars and fast transients
with the Low-Frequency Array (LOFAR) around 140 MHz and here report on the
first low-frequency fast-radio burst limit and the discovery of two new
pulsars. The first survey, the LOFAR Pilot Pulsar Survey (LPPS), observed a
large fraction of the northern sky, ~1.4 x 10^4 sq. deg, with 1-hr dwell times.
Each observation covered ~75 sq. deg using 7 independent fields formed by
incoherently summing the high-band antenna fields. The second pilot survey, the
LOFAR Tied-Array Survey (LOTAS), spanned ~600 sq. deg, with roughly a 5-fold
increase in sensitivity compared with LPPS. Using a coherent sum of the 6 LOFAR
"Superterp" stations, we formed 19 tied-array beams, together covering 4 sq.
deg per pointing. From LPPS we derive a limit on the occurrence, at 142 MHz, of
dispersed radio bursts of 107 Jy
for the narrowest searched burst duration of 0.66 ms. In LPPS, we re-detected
65 previously known pulsars. LOTAS discovered two pulsars, the first with LOFAR
or any digital aperture array. LOTAS also re-detected 27 previously known
pulsars. These pilot studies show that LOFAR can efficiently carry out all-sky
surveys for pulsars and fast transients, and they set the stage for further
surveying efforts using LOFAR and the planned low-frequency component of the
Square Kilometer Array.Comment: 18 pages, 10 figures, accepted for A&
Van Warder naar Zwitserland: Op het spoor van de fluit
Een dwarsfluit uit het begin van de zestiende eeuw. Die doken archeologen op uit een scheepswrak in het Markermeer. Alleen dat al is een extreem zeldzame gebeurtenis. Maar van wie kan die fluit geweest zijn? Een stuk papier bij het mondgat zet een gevarieerd team van deskundigen op een spoor dat warmer en warmer word
Combining solvents and surfactants for inkjet printing PEDOT: PSS on P3HT/PCBM in organic solar cells
A commonly used strategy in the fabrication of organic electronics involves the use of orthogonal solvents, i.e. the alternating use of organic solvents and water for the application of consecutive layers to prevent dissolution of previous layers. This strategy therefore requires the deposition of sequential layers with a large mismatch in surface energy. In case of organic photovoltaics (OPV) a particularly challenging deposition is that of the aqueous Poly(3,4-ethylenedioxythiophene) Polystyrene sulfonate (PEDOT:PSS) on the hydrophobic Poly(3-hexylthiophene-2,5-diyl/Phenyl-C61-butyric acid methyl ester (P3HT/PCBM) layer. The mismatch in surface energy causes dewetting and inhomogeneous layer formation. In inkjet printing individually placed droplets should spread sufficiently far to form a homogeneous closed layer before the solvents in the droplet evaporate. A formulation for the aqueous PEDOT:PSS layer has been developed in which the combination of solvents and surfactants is essential for achieving a homogenous layer on the timescales needed for inkjet printing. Homogenous layers of PEDOT:PSS on P3HT/PCBM were achieved for layer thicknesses from 400 nm to 50 nm. The efficiency of the OPV's fabricated with the new formulation were comparable with reference devices, where evaporated molybdenum oxide (MoOx) was used as a topelectrode. This shows that by the addition of solvents and surfactants a hydrophilic solution can be inkjet printed successfully to form homogenous layers on hydrophobic surfaces and achieve good efficiencies in an inverted organic solar cell.Green Open Access added to TU Delft Institutional Repository âYou share, we take care!â â Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Novel Aerospace Material