3,271 research outputs found
Adventures of a tidally induced bar
Using N-body simulations, we study the properties of a bar induced in a discy dwarf galaxy as a result of tidal interaction with the Milky Way. The bar forms at the first pericentre passage and survives until the end of the evolution at 10 Gyr. Fourier decomposition of the bar reveals that only even modes are significant and preserve a hierarchy so that the bar mode is always the strongest. They show a characteristic profile with a maximum, similar to simulated bars forming in isolated galaxies and observed bars in real galaxies. We adopt the maximum of the bar mode as a measure of the bar strength and we estimate the bar length by comparing the density profiles along the bar and perpendicular to it. The bar strength and the bar length decrease with time, mainly at pericentres, as a result of tidal torques acting at those times and not to secular evolution. The pattern speed of the bar varies significantly on a time-scale of 1 Gyr and is controlled by the orientation of the tidal torque from the Milky Way. The bar is never tidally locked, but we discover a hint of a 5/2 orbital resonance between the third and fourth pericentre passage. The speed of the bar decreases in the long run so that the bar changes from initially rather fast to slow in the later stages. The boxy/peanut shape is present for some time and its occurrence is preceded by a short period of buckling instability
Galaxy cluster mergers as triggers for the formation of jellyfish galaxies: case study of the A901/2 system
The A901/2 system is a rare case of galaxy cluster interaction, in which two
galaxy clusters and two smaller groups are seen in route of collision with each
other simultaneously. Within each of the four substructures, several galaxies
with features indicative of jellyfish morphologies have been observed. In this
paper, we propose a hydrodynamic model for the merger as a whole, compatible
with its diffuse X-ray emission, and correlate the gas properties in this model
with the locations of the jellyfish galaxy candidates in the real system. We
find that jellyfish galaxies seem to be preferentially located near a boundary
inside each subcluster where diffuse gas moving along with the subcluster and
diffuse gas from the remainder of the system meet. The velocity change in those
boundaries is such that a factor of up to 1000 increase in the ram
pressure takes place within a few hundred kpc, which could trigger the high
rate of gas loss necessary for a jellyfish morphology to emerge. A theoretical
treatment of ram pressure stripping in the environment of galaxy cluster
mergers has not been presented in the literature so far; we propose that this
could be a common scenario for the formation of jellyfish morphologies in such
systems.Comment: Accepted for publication in MNRAS. 10 pages, 9 figure
Sign-changing tower of bubbles for a sinh-Poisson equation with asymmetric exponents
Motivated by the statistical mechanics description of stationary
2D-turbulence, for a sinh-Poisson type equation with asymmetric nonlinearity,
we construct a concentrating solution sequence in the form of a tower of
singular Liouville bubbles, each of which has a different degeneracy exponent.
The asymmetry parameter corresponds to the ratio between the
intensity of the negatively rotating vortices and the intensity of the
positively rotating vortices. Our solutions correspond to a superposition of
highly concentrated vortex configurations of alternating orientation; they
extend in a nontrivial way some known results for . Thus, by
analyzing the case we emphasize specific properties of the
physically relevant parameter in the vortex concentration phenomena
Comparison of direct and indirect methods to maximise the detection of Babesia caballi and Theileria equi infections in Central Southern Italy
: Equine piroplasmosis is a disease of equids, caused by tick-borne apicomplexan protozoan pathogens Babesia caballi and Theileria equi, which, according to the World Organisation for Animal Health (OIE), can be diagnosed by enzyme-linked immunosorbent assay (ELISA), immunofluorescent antibody test (IFAT) and polymerase chain reaction (PCR). The present study was conducted to evaluate and compare the assays available for the diagnosis of equine piroplasmosis. Data employed were obtained from 1300 blood samples collected between 2012-2014 from asymptomatic and symptomatic equines (horses and donkeys) of central-southern regions of Italy and analyzed by ELISA, IFAT, PCR (one commercial and one from literature) and blood smear microscopic examination. Statistical differences of the proportions of positivity for each parasite and group (asymptomatic and symptomatic) among the methods were verified by the z test to identify the most sensitive. The concordance between each pair of methods - for each parasite and within the groups - and trends in detection of suspect samples of four hypothetical diagnostic algorithms using serological and biomolecular assays were evaluated to identify the most suitable laboratory diagnostic workflow. The results of this study highlighted a lower capacity to detect suspect samples of commercial ELISA for B. caballi in all groups when compared to biomolecular methods and IFAT; and of the commercial PCRs in asymptomatic animals, identifying a PCR from literature and IFAT as the best choice for a combined diagnosis. For T. equi, IFAT detected more suspect samples than ELISA, even if the latter showed good performance and some samples were positive only by the ELISA and PCR, indicating that their simultaneous employment is still advantageous. Host-parasite interaction, amino-acid/genetic diversity and differences in detection limits among the assays could be among the reasons in explaining the present results. In view of further studies, ELISA should be used in combination with PCR, that should regularly be included in the laboratory diagnosis to maximise the detection of early infections and support the evaluation of pharmacological treatment
On the structure of phase transition maps for three or more coexisting phases
This paper is partly based on a lecture delivered by the author at the ERC
workshop "Geometric Partial Differential Equations" held in Pisa in September
2012. What is presented here is an expanded version of that lecture.Comment: 23 pages, 6 figure
Role of Linker Functionality in Polymers Exhibiting Main-Chain Thermally Activated Delayed Fluorescence
Excellent performance has been reported for organic light‐emitting diodes (OLEDs) based on small molecule emitters that exhibit thermally activated delayed fluorescence. However, the necessary vacuum processing makes the fabrication of large‐area devices based on these emitters cumbersome and expensive. Here, the authors present high performance OLEDs, based on novel, TADF polymers that can be readily processed from a solution. These polymers are based on the acridine‐benzophenone donor–acceptor motif as main‐chain TADF chromophores, linked by various conjugated and non‐conjugated spacer moieties. The authors’ extensive spectroscopic and electronic analysis shows that in particular in case of alkyl spacers, the properties and performance of the monomeric TADF chromophores are virtually left unaffected by the polymerization. They present efficient solution‐processed OLEDs based on these TADF polymers, diluted in oligostyrene as a host. The devices based on the alkyl spacer‐based TADF polymers exhibit external quantum efficiencies (EQEs) ≈12%, without any outcoupling‐enhancing measures. What's more, the EQE of these devices does not drop substantially upon diluting the polymer down to only ten weight percent of active material. In contrast, the EQE of devices based on the monomeric chromophore show significant losses upon dilution due to loss of charge percolation
Resumption of postpartum ovarian cyclicity in dairy cows and its relationship with acute phase proteins, uterine health and lipolysis during the transition period.
O objetivo deste estudo foi avaliar a retomada do pós-parto ciclicidade e sua relação com proteínas de fase aguda, a saúde uterina e lipólise durante o período de transição de vacas leiteiras
Semeadura direta como estratégia de implantação do componente arbóreo de agroflorestas.
Os sistemas agroflorestais (SAF) são uma forma de agricultura ancestral, onde árvores e culturas agrícolas (anuais ou perenes) são cultivadas de forma consorciada no tempo e/ou espaço
Prepartum body condition score changes and the secretion of acute phase proteins in dairy cows.
O objetivo deste estudo foi investigar o efeito da condição corporal (BCS) durante o período de pré-parto, sobre a concentração de proteínas de fase aguda e parâmetros metabólicos em vacas leiteiras
Ginzburg-Landau model with small pinning domains
We consider a Ginzburg-Landau type energy with a piecewise constant pinning
term in the potential . The function is different from
1 only on finitely many disjoint domains, called the {\it pinning domains}.
These pinning domains model small impurities in a homogeneous superconductor
and shrink to single points in the limit ; here, \v is the inverse of
the Ginzburg-Landau parameter. We study the energy minimization in a smooth
simply connected domain with Dirichlet boundary
condition on \d \O, with topological degree {\rm deg}_{\d \O} (g) = d
>0. Our main result is that, for small \v, minimizers have distinct
zeros (vortices) which are inside the pinning domains and they have a degree
equal to 1. The question of finding the locations of the pinning domains with
vortices is reduced to a discrete minimization problem for a finite-dimensional
functional of renormalized energy. We also find the position of the vortices
inside the pinning domains and show that, asymptotically, this position is
determined by {\it local renormalized energy} which does not depend on the
external boundary conditions.Comment: 39 page
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