1,532 research outputs found
Effect of dephasing on the current statistics of mesoscopic devices
We investigate the effects of dephasing on the current statistics of
mesoscopic conductors with a recently developed statistical model, focusing in
particular on mesoscopic cavities and Aharonov-Bohm rings. For such devices, we
analyze the influence of an arbitrary degree of decoherence on the cumulants of
the current. We recover known results for the limiting cases of fully coherent
and totally incoherent transport and are able to obtain detailed information on
the intermediate regime of partial coherence for a varying number of open
channels. We show that dephasing affects the average current, shot noise, and
higher order cumulants in a quantitatively and qualitatively similar way, and
that consequently shot noise or higher order cumulants of the current do not
provide information on decoherence additional or complementary to what can be
already obtained from the average current.Comment: 4 pages, 4 figure
Statistical model of dephasing in mesoscopic devices introduced in the scattering matrix formalism
We propose a phenomenological model of dephasing in mesoscopic transport,
based on the introduction of random phase fluctuations in the computation of
the scattering matrix of the system. A Monte Carlo averaging procedure allows
us to extract electrical and microscopic device properties. We show that, in
this picture, scattering matrix properties enforced by current conservation and
time reversal invariance still hold. In order to assess the validity of the
proposed approach, we present simulations of conductance and magnetoconductance
of Aharonov-Bohm rings that reproduce the behavior observed in experiments, in
particular as far as aspects related to decoherence are concerned.Comment: 6 pages, 6 figure
Cellulose-binding domains as a tool for paper recycling
Treatment of secondary paper fibres with cellulose-binding domains allows for improvements of pulp drainability and of paper mechanical properties. The interfacial system fibrewater- fibre, and after drying, fibre-air-fibre, may be affected by the CBD treatment, influencing the pulp and paper technical properties. Inverse Gas Chromatography provides experimental evidence that support this hypothesis
Towards a volumetric census of close white dwarf binaries I.Reference samples
Close white dwarf binaries play an important role across a range of
astrophysics, including thermonuclear supernovae, the Galactic low-frequency
gravitational wave signal, and the chemical evolution of the Galaxy. Progress
in developing a detailed understanding of the complex, multi-threaded
evolutionary pathways of these systems is limited by the lack of statistically
sound observational constraints on the relative fractions of various
sub-populations, and their physical properties. The available samples are
small, heterogeneous, and subject to a multitude of observational biases. Our
overarching goal is to establish a volume-limited sample of all types of white
dwarf binaries that is representative of the underlying population as well as
sufficiently large to serve as a benchmark for future binary population models.
In this first paper, we provide an overview of the project, and assemble
reference samples within a distance limit of 300\,pc of known white dwarf
binaries spanning the most common sub-classes: post-common envelope binaries
containing a white dwarf plus a main sequence star, cataclysmic variables and
double-degenerate binaries. We carefully vet the members of these "Gold"
Samples, which span most of the evolutionary parameter space of close white
dwarf binary evolution. We also explore the differences between magnitude and
volume limited close white dwarf binary samples, and discuss how these systems
evolve in their observational properties across the Gaia Hertzsprung-Russell
diagram.Comment: Accepted for publication in MNRAS on 11/3/2021 following peer revie
Introducing 12 new dyes for use with oligonucleotide functionalised silver nanoparticles for DNA detection with SERS
Oligonucleotide functionalised metallic nanoparticles (MNPs) have been shown to be an effective tool in the detection of disease-specific DNA and have been employed in a number of diagnostic assays. The MNPs are also capable of facilitating surface enhanced Raman scattering (SERS) enabling detection to become highly sensitive. Herein we demonstrate the expansion of the range of specific SERS-active oligonucleotide MNPs through the use of 12 new Raman-active monomethine and trimethine chalcogenopyrylium and benzochalcogenopyrylium derivatives. This has resulted in an increased ability to carry out multiplexed analysis beyond the current small pool of resonant and non-resonant Raman active molecules, that have been used with oligonucleotide functionalised nanoparticles. Each dye examined here contains a variation of sulphur and selenium atoms in the heterocyclic core, together with phenyl, 2-thienyl, or 2-selenophenyl substituents on the 2,2’,6, and 6’ positions of the chalcogenopyrylium dyes and 2 and 2’ positions of the benzochalcogenopyrylium dyes. The intensity of SERS obtained from each dye upon conjugate hybridisation with a complementary single stranded piece of DNA was explored. Differing concentrations of each dye (1000, 3000, 5000 and 7000 equivalents per NP-DNA conjugate) were used to understand the effects of Raman reporter coating on the overall Raman intensity. It was discovered that dye concentration did not affect the target/control ratio, which remained relatively constant throughout and that a lower concentration of Raman reporter was favourable in order to avoid NP instability. A relationship between the dye structure and SERS intensity was discovered, leaving scope for future development of specific dyes containing substituents favourable for discrimination in a multiplex by SERS. Methine dyes containing S and Se in the backbone and at least 2 phenyls as substituents give the highest SERS signal following DNA-induced aggregation. Principal component analysis (PCA) was performed on the data to show differentiation between the dye classes and highlight possible future multiplexing capabilities of the 12 investigated dyes
Efeito do período de subcultivo sobre a indução de calos embriogênicos em explantes foliares de cafeeiro.
Efeito do sistema de cultivo e do meio de cultura sobre o crescimento de calos embriogênicos de cafeeiro.
Neste trabalho comparou-se a produção de calos embriogênicos em meio líquido com a de meio gelificado usando-se dois meios de cultura recomendados para café arábica: CP (van Boxtel & Berthouly, 1996) e SM (Teixeira et al. 2004
Crescimento de calos embriogênicos de diferentes genótipos de café em meio de cultura líguido.
The Organization of the Pig T-Cell Receptor γ (TRG) Locus Provides Insights into the Evolutionary Patterns of the TRG Genes across Cetartiodactyla
The domestic pig (Sus scrofa) is a species representative of the Suina, one of the four suborders within Cetartiodactyla. In this paper, we reported our analysis of the pig TRG locus in comparison with the loci of species representative of the Ruminantia, Tylopoda, and Cetacea suborders. The pig TRG genomic structure reiterates the peculiarity of the organization of Cetartiodactyla loci in TRGC "cassettes", each containing the basic V-J-J-C unit. Eighteen genes arranged in four TRGC cassettes, form the pig TRG locus. All the functional TRG genes were expressed, and the TRGV genes preferentially rearrange with the TRGJ genes within their own cassette, which correlates the diversity of the γ-chain repertoire with the number of cassettes. Among them, the TRGC5, located at the 5' end of the locus, is the only cassette that retains a marked homology with the corresponding TRGC cassettes of all the analyzed species. The preservation of the TRGC5 cassette for such a long evolutionary time presumes a highly specialized function of its genes, which could be essential for the survival of species. Therefore, the maintenance of this cassette in pigs confirms that it is the most evolutionarily ancient within Cetartiodactyla, and it has undergone a process of duplication to give rise to the other TRGC cassettes in the different artiodactyl species in a lineage-specific manner
Accurate mass-radius ratios for Hyades white dwarfs
We use the ESPRESSO spectrograph at the Very Large Telescope to measure
velocity shifts and gravitational redshifts of eight bona fide Hyades white
dwarfs, with an accuracy better than 1.5 percent. By comparing the
gravitational redshift measurements of the mass-to-radius ratio with the same
ratios derived by fitting the \textit{Gaia} photometry with theoretical models,
we find an agreement to better than one per cent. It is possible to reproduce
the observed white dwarf cooling sequence and the trend of the mass-to-radius
ratios as a function of colour using isochrones with ages between 725 and 800
Myr, tuned for the Hyades. One star, EGGR\,29, consistently stands out in all
diagrams, indicating that it is possibly the remnant of a blue straggler. We
also computed mass-to-radius ratios from published gravities and masses,
determined from spectroscopy. The comparison between photometric and
spectroscopic stellar parameters reveals that spectroscopic effective
temperature and gravity are systematically larger than the photometric values.
Spectroscopic mass-to-radius ratios disagree with those measured from
gravitational redshift, indicating the presence of systematics affecting the
white dwarf parameters derived from the spectroscopic analysis.Comment: MNRAS, accepted for pubblicatio
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