3,746 research outputs found
Single nucleotide polymorphisms to discriminate different classes of hybrid between wild Atlantic salmon and aquaculture escapees
201
Universal Crossover between Efros-Shklovskii and Mott Variable-Range-Hopping Regimes
A universal scaling function, describing the crossover between the Mott and
the Efros-Shklovskii hopping regimes, is derived, using the percolation picture
of transport in strongly localized systems. This function is agrees very well
with experimental data. Quantitative comparison with experiment allows for the
possible determination of the role played by polarons in the transport.Comment: 7 pages + 1 figure, Revte
Penetration of hot electrons through a cold disordered wire
We study a penetration of an electron with high energy E<<T through strongly
disordered wire of length L<<a (a being the localization length). Such an
electron can loose, but not gain the energy, when hopping from one localized
state to another. We have found a distribution function for the transmission
coefficient t. The typical t remains exponentially small in L/a, but with the
decrement, reduced compared to the case of direct elastic tunnelling. The
distribution function has a relatively strong tail in the domain of anomalously
high t; the average ~(a/L)^2 is controlled by rare configurations of
disorder, corresponding to this tail.Comment: 4 pages, 5 figure
Neuronal chemotaxis by optically manipulated liposomes
We probe chemotaxis of single neurons, induced by signalling molecules which were optically delivered from liposomes in the neighbourhood of the cells. We implemented an optical tweezers setup combined with a micro-dissection system on an inverted microscope platform. Molecules of Netrin-1 protein were encapsulated into micron-sized liposomes and manipulated to micrometric distances from a specific growth cone of a hippocampal neuron by the IR optical tweezers. The molecules were then released broken the liposomes with UV laser pulses. Chemotaxis induced by the delivered molecules was confirmed by the migration of the growth cone toward the liposome position. Since the delivery can be manipulated with high temporal and spatial resolution and the number of molecules released can be controlled quite precisely by tuning the liposome size and the solution concentration, this technique opens new opportunities to investigate the effect of physiological active compounds as Netrin-1 to neuronal signalling and guidance, which represents an important issue in neurobiology
Identification of Tinomiscium petiolare from Vietnam using the DNA barcode
Background. Tinomiscium petiolare Hook.f. & Thomson is a medicinal species of the family Menispermaceae. This species is currently being intensively exploited for therapeutic purposes. Precise and rapid identification of T. petiolare is critical and essential for the classification, propagation, use and conservation of its genetic resources. In recent years, DNA barcoding has been known to be a fast and sensitive method for identifying species at any stage of development, using short DNA sequences. In this study we have performed the identification of T. petiolare specimens in Vietnam based on the sequence analysis of 4 DNA barcode loci: ITS, matK, rbcL and rpoC.Materials and methods. Total DNA was extracted from leaf samples using DNeasy Plant Mini Kit. PCR amplification of the ITS, matK, rbcL and rpoC regions was carried out on the GeneAmp PCR System 9700 with specific primers. The purified PCR products were sequenced on the ABI 3500 Genetic Analyzer system, using BigDye®Terminator v3.1 Cycle Sequencing Kit. These genetic sequences were analyzed and compared, and a phylogenetic tree was constructed using BioEdit, BLAST, and MEGA 6 programs.Results and conclusion. The success rate of amplification and sequencing was 100% for all 4 DNA barcode loci (ITS, matK, rbcL and rpoC) in the studied specimens. The produced sequence sizes of ITS, matK, rbcL and rpoC in the specimens were 574 bp, 810 bp, 527 bp and 488 bp, respectively. Further, we identified that all studied specimens were genetically related to each other and associated with the same species T. petiolare. Overall, the results of the study generated the most complete DNA barcode database of T. petiolare collected in Vietnam, contributing to the taxonomy and identification of this species
ALKBH8-mediated formation of a novel diastereomeric pair of wobble nucleosides in mammalian tRNA
Mammals have nine different homologues (ALKBH1–9) of the Escherichia coli DNA repair demethylase AlkB. ALKBH2 is a genuine DNA repair enzyme, but the in vivo function of the other ALKBH proteins has remained elusive. It was recently shown that ALKBH8 contains an additional transfer RNA (tRNA) methyltransferase domain, which generates the wobble nucleoside 5-methoxycarbonylmethyluridine (mcm5U) from its precursor 5-carboxymethyluridine (cm5U). In this study, we report that (R)- and (S)-5-methoxycarbonylhydroxymethyluridine (mchm5U), hydroxylated forms of mcm5U, are present in mammalian , and , respectively, representing the first example of a diastereomeric pair of modified RNA nucleosides. Through in vitro and in vivo studies, we show that both diastereomers of mchm5U are generated from mcm5U, and that the AlkB domain of ALKBH8 specifically hydroxylates mcm5U into (S)-mchm5U in . These findings expand the function of the ALKBH oxygenases beyond nucleic acid repair and increase the current knowledge on mammalian wobble uridine modifications and their biogenesis
Joint PDF modelling of turbulent flow and dispersion in an urban street canyon
The joint probability density function (PDF) of turbulent velocity and
concentration of a passive scalar in an urban street canyon is computed using a
newly developed particle-in-cell Monte Carlo method. Compared to moment
closures, the PDF methodology provides the full one-point one-time PDF of the
underlying fields containing all higher moments and correlations. The
small-scale mixing of the scalar released from a concentrated source at the
street level is modelled by the interaction by exchange with the conditional
mean (IECM) model, with a micro-mixing time scale designed for geometrically
complex settings. The boundary layer along no-slip walls (building sides and
tops) is fully resolved using an elliptic relaxation technique, which captures
the high anisotropy and inhomogeneity of the Reynolds stress tensor in these
regions. A less computationally intensive technique based on wall functions to
represent boundary layers and its effect on the solution are also explored. The
calculated statistics are compared to experimental data and large-eddy
simulation. The present work can be considered as the first example of
computation of the full joint PDF of velocity and a transported passive scalar
in an urban setting. The methodology proves successful in providing high level
statistical information on the turbulence and pollutant concentration fields in
complex urban scenarios.Comment: Accepted in Boundary-Layer Meteorology, Feb. 19, 200
The stress hormone corticosterone in a marine top predatorreflects short-term changes in food availability
-In many seabird studies, single annual proxies of prey abundance have been
used to explain variability in breeding performance, but much more important
is probably the timing of prey availability relative to the breeding season when
energy demand is at a maximum. Until now, intraseasonal variation in prey
availability has been difficult to quantify in seabirds. Using a state-of-the-art
ocean drift model of larval cod Gadus morhua, an important constituent of the
diet of common guillemots Uria aalge in the southwestern Barents Sea, we were
able to show clear, short-term correlations between food availability and measurements
of the stress hormone corticosterone (CORT) in parental guillemots
over a 3-year period (2009–2011). The model allowed the extraction of abundance
and size of cod larvae with very high spatial (4 km) and temporal resolutions
(1 day) and showed that cod larvae from adjacent northern spawning
grounds in Norway were always available near the guillemot breeding colony
while those from more distant southerly spawning grounds were less frequent,
but larger. The latter arrived in waves whose magnitude and timing, and thus
overlap with the guillemot breeding season, varied between years. CORT levels
in adult guillemots were lower in birds caught after a week with high frequencies
of southern cod larvae. This pattern was restricted to the two years (2009
and 2010) in which southern larvae arrived before the end of the guillemot
breeding season. Any such pattern was masked in 2011 by already exceptionally
high numbers of cod larvae in the region throughout chick-rearing period. The
findings suggest that CORT levels in breeding birds increase when the arrival of
southern sizable larvae does not match the period of peak energy requirements
during breeding.
Common guillemot, CORT, food availability,
seabird, Uria aalg
The central engine of GRB 130831A and the energy breakdown of a relativistic explosion
Gamma-ray bursts (GRBs) are the most luminous explosions in the universe, yet
the nature and physical properties of their energy sources are far from
understood. Very important clues, however, can be inferred by studying the
afterglows of these events. We present optical and X-ray observations of GRB
130831A obtained by Swift, Chandra, Skynet, RATIR, Maidanak, ISON, NOT, LT and
GTC. This burst shows a steep drop in the X-ray light-curve at s
after the trigger, with a power-law decay index of . Such a rare
behaviour cannot be explained by the standard forward shock (FS) model and
indicates that the emission, up to the fast decay at s, must be of
"internal origin", produced by a dissipation process within an
ultrarelativistic outflow. We propose that the source of such an outflow, which
must produce the X-ray flux for day in the cosmological rest frame,
is a newly born magnetar or black hole. After the drop, the faint X-ray
afterglow continues with a much shallower decay. The optical emission, on the
other hand, shows no break across the X-ray steep decrease, and the late-time
decays of both the X-ray and optical are consistent. Using both the X-ray and
optical data, we show that the emission after s can be explained
well by the FS model. We model our data to derive the kinetic energy of the
ejecta and thus measure the efficiency of the central engine of a GRB with
emission of internal origin visible for a long time. Furthermore, we break down
the energy budget of this GRB into the prompt emission, the late internal
dissipation, the kinetic energy of the relativistic ejecta, and compare it with
the energy of the associated supernova, SN 2013fu.Comment: Accepted for publication by MNRAS. 21 pages, 3 figures, 8 tables.
Extra table with magnitudes in the sourc
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