469 research outputs found
Political polarization of news media and influencers on Twitter in the 2016 and 2020 US presidential elections
Social media has been transforming political communication dynamics for over a decade. Here using nearly a billion tweets, we analyse the change in Twitter’s news media landscape between the 2016 and 2020 US presidential elections. Using political bias and fact-checking tools, we measure the volume of politically biased content and the number of users propagating such information. We then identify influencers—users with the greatest ability to spread news in the Twitter network. We observe that the fraction of fake and extremely biased content declined between 2016 and 2020. However, results show increasing echo chamber behaviours and latent ideological polarization across the two elections at the user and influencer levels
Placenta-Derived Fetal Specific mRNA Is More Readily Detectable in Maternal Plasma than in Whole Blood
BACKGROUND:Placental mRNA was detected in maternal whole blood, raising the possibility of using maternal blood for noninvasive prenatal diagnosis. We investigated fetal mRNA detection in maternal whole blood and determined if it offered advantages over maternal plasma analysis. METHODOLOGY:The concentrations of placental expressed genes, CSH1, KISS1, PLAC4 and PLAC1 in plasma and whole blood from healthy pregnant and non-pregnant individuals were compared by real-time quantitative reverse-transcriptase polymerase chain reaction analysis. Their fetal specificity was investigated by comparing the transcript concentrations in pre- and post-delivery samples and through SNP genotyping by matrix-assisted laser-desorption and ionization time-of-flight mass spectrometry. The gene expression profiles of pregnant and non-pregnant whole blood were investigated by microarray analysis. Upregulated genes in pregnant whole blood were selected for further quantitative analysis. PRINCIPAL FINDINGS:The concentrations of the four transcripts were significantly higher in third trimester maternal whole blood than corresponding plasma without significant correlations. KISS1, PLAC4 and PLAC1 were detected in non-pregnant whole blood but not plasma. The transcripts remained detectable in some postpartum whole blood samples. The PLAC4 mRNA in maternal plasma showed fetal genotype while that in corresponding whole blood indicated both fetal and maternal contributions. Microarray analysis revealed upregulation of genes involved in neutrophil functions in pregnant whole blood including DEFA4, CEACAM8, OLFM4, ORM1, MMP8 and MPO. Though possibly pregnancy-related, they were not pregnancy-specific as suggested by the lack of post-delivery reduction in concentrations. CONCLUSIONS:Maternal plasma is preferred over maternal whole blood for placenta-derived fetal RNA detection. Most studied 'placental' mRNA molecules in maternal whole blood were of maternal origin and might be derived from processes such as 'illegitimate transcription'
Coexistence of Merons with Skyrmions in the Centrosymmetric van der Waals Ferromagnet Fe5GeTe2
FeGeTe is a centrosymmetric, layered van der Waals (vdW)
ferromagnet that displays Curie temperatures (270-330 K) that are within
the useful range for spintronic applications. However, little is known about
the interplay between its topological spin textures (e.g., merons, skyrmions)
with technologically relevant transport properties such as the topological Hall
effect (THE), or topological thermal transport. Here, we show via
high-resolution Lorentz transmission electron microscopy that merons and
anti-meron pairs coexist with N\'{e}el skyrmions in FeGeTe over a
wide range of temperatures and probe their effects on thermal and electrical
transport. We detect a THE, even at room , that senses merons at higher s
as well as their coexistence with skyrmions as is lowered indicating an
on-demand thermally driven formation of either type of spin texture.
Remarkably, we also observe an unconventional THE in absence of Lorentz force
and attribute it to the interaction between charge carriers and magnetic
field-induced chiral spin textures. Our results expose FeGeTe as a
promising candidate for the development of applications in skyrmionics/meronics
due to the interplay between distinct but coexisting topological magnetic
textures and unconventional transport of charge/heat carriers.Comment: In press. Four figures in the main text. Includes SI file with 19
additional figure
Anomalous metamagnetism in the low carrier density Kondo lattice YbRh3Si7
We report complex metamagnetic transitions in single crystals of the new low
carrier Kondo antiferromagnet YbRh3Si7. Electrical transport, magnetization,
and specific heat measurements reveal antiferromagnetic order at T_N = 7.5 K.
Neutron diffraction measurements show that the magnetic ground state of
YbRh3Si7 is a collinear antiferromagnet where the moments are aligned in the ab
plane. With such an ordered state, no metamagnetic transitions are expected
when a magnetic field is applied along the c axis. It is therefore surprising
that high field magnetization, torque, and resistivity measurements with H||c
reveal two metamagnetic transitions at mu_0H_1 = 6.7 T and mu_0H_2 = 21 T. When
the field is tilted away from the c axis, towards the ab plane, both
metamagnetic transitions are shifted to higher fields. The first metamagnetic
transition leads to an abrupt increase in the electrical resistivity, while the
second transition is accompanied by a dramatic reduction in the electrical
resistivity. Thus, the magnetic and electronic degrees of freedom in YbRh3Si7
are strongly coupled. We discuss the origin of the anomalous metamagnetism and
conclude that it is related to competition between crystal electric field
anisotropy and anisotropic exchange interactions.Comment: 23 pages and 4 figures in the main text. 7 pages and 5 figures in the
supplementary materia
Writing and detecting topological charges in exfoliated FeGeTe
FeGeTe is a promising two-dimensional (2D) van der Waals (vdW)
magnet for practical applications, given its magnetic properties. These include
Curie temperatures above room temperature, and topological spin textures (TST
or both merons and skyrmions), responsible for a pronounced anomalous Hall
effect (AHE) and its topological counterpart (THE), which can be harvested for
spintronics. Here, we show that both the AHE and THE can be amplified
considerably by just adjusting the thickness of exfoliated FeGeTe,
with THE becoming observable even in zero magnetic field due to a field-induced
unbalance in topological charges. Using a complementary suite of techniques,
including electronic transport, Lorentz transmission electron microscopy, and
micromagnetic simulations, we reveal the emergence of substantial coercive
fields upon exfoliation, which are absent in the bulk, implying
thickness-dependent magnetic interactions that affect the TST. We detected a
``magic" thickness 30 nm where the formation of TST is maximized,
inducing large magnitudes for the topological charge density ( cm), and the concomitant anomalous ( cm) and topological ( cm) Hall resistivities at ~ 120 K. These values for
and are higher than those
found in magnetic topological insulators and, so far, the largest reported for
2D magnets. The hitherto unobserved THE under zero magnetic field could provide
a platform for the writing and electrical detection of TST aiming at
energy-efficient devices based on vdW ferromagnets.Comment: 45 pages with supporting information file, 5 main figures. Accepted
ACS Nano 202
Individualization as driving force of clustering phenomena in humans
One of the most intriguing dynamics in biological systems is the emergence of
clustering, the self-organization into separated agglomerations of individuals.
Several theories have been developed to explain clustering in, for instance,
multi-cellular organisms, ant colonies, bee hives, flocks of birds, schools of
fish, and animal herds. A persistent puzzle, however, is clustering of opinions
in human populations. The puzzle is particularly pressing if opinions vary
continuously, such as the degree to which citizens are in favor of or against a
vaccination program. Existing opinion formation models suggest that
"monoculture" is unavoidable in the long run, unless subsets of the population
are perfectly separated from each other. Yet, social diversity is a robust
empirical phenomenon, although perfect separation is hardly possible in an
increasingly connected world. Considering randomness did not overcome the
theoretical shortcomings so far. Small perturbations of individual opinions
trigger social influence cascades that inevitably lead to monoculture, while
larger noise disrupts opinion clusters and results in rampant individualism
without any social structure. Our solution of the puzzle builds on recent
empirical research, combining the integrative tendencies of social influence
with the disintegrative effects of individualization. A key element of the new
computational model is an adaptive kind of noise. We conduct simulation
experiments to demonstrate that with this kind of noise, a third phase besides
individualism and monoculture becomes possible, characterized by the formation
of metastable clusters with diversity between and consensus within clusters.
When clusters are small, individualization tendencies are too weak to prohibit
a fusion of clusters. When clusters grow too large, however, individualization
increases in strength, which promotes their splitting.Comment: 12 pages, 4 figure
Cooperation, Norms, and Revolutions: A Unified Game-Theoretical Approach
Cooperation is of utmost importance to society as a whole, but is often
challenged by individual self-interests. While game theory has studied this
problem extensively, there is little work on interactions within and across
groups with different preferences or beliefs. Yet, people from different social
or cultural backgrounds often meet and interact. This can yield conflict, since
behavior that is considered cooperative by one population might be perceived as
non-cooperative from the viewpoint of another.
To understand the dynamics and outcome of the competitive interactions within
and between groups, we study game-dynamical replicator equations for multiple
populations with incompatible interests and different power (be this due to
different population sizes, material resources, social capital, or other
factors). These equations allow us to address various important questions: For
example, can cooperation in the prisoner's dilemma be promoted, when two
interacting groups have different preferences? Under what conditions can costly
punishment, or other mechanisms, foster the evolution of norms? When does
cooperation fail, leading to antagonistic behavior, conflict, or even
revolutions? And what incentives are needed to reach peaceful agreements
between groups with conflicting interests?
Our detailed quantitative analysis reveals a large variety of interesting
results, which are relevant for society, law and economics, and have
implications for the evolution of language and culture as well
Spatial interactions in agent-based modeling
Agent Based Modeling (ABM) has become a widespread approach to model complex
interactions. In this chapter after briefly summarizing some features of ABM
the different approaches in modeling spatial interactions are discussed.
It is stressed that agents can interact either indirectly through a shared
environment and/or directly with each other. In such an approach, higher-order
variables such as commodity prices, population dynamics or even institutions,
are not exogenously specified but instead are seen as the results of
interactions. It is highlighted in the chapter that the understanding of
patterns emerging from such spatial interaction between agents is a key problem
as much as their description through analytical or simulation means.
The chapter reviews different approaches for modeling agents' behavior,
taking into account either explicit spatial (lattice based) structures or
networks. Some emphasis is placed on recent ABM as applied to the description
of the dynamics of the geographical distribution of economic activities, - out
of equilibrium. The Eurace@Unibi Model, an agent-based macroeconomic model with
spatial structure, is used to illustrate the potential of such an approach for
spatial policy analysis.Comment: 26 pages, 5 figures, 105 references; a chapter prepared for the book
"Complexity and Geographical Economics - Topics and Tools", P. Commendatore,
S.S. Kayam and I. Kubin, Eds. (Springer, in press, 2014
Useful immunohistochemical indicators in canine mast cell tumours
Morphological and immunohistochemical analysis of 45 canine mast cell tumours was performed to determine whether the proteins examined are useful for a more precise description of tumour morphology and a more reliable determination of the prognosis in patients. Tissue sections were stained according to the standard haematoxylin and eosin (HE) technique and with toluidine blue to demonstrate cytoplasmic granules. Immunohistochemical studies were performed, using the cell markers CD117 (c-kit), p16 and von Willebrand factor (FVIII). In CD117 three different staining patterns were observed: (1) membranous reaction, (2) intense staining of cytoplasm, and (3) a diffuse, delicate cytoplasmic reaction. Von Willebrand antibody was evaluated on the basis of the number of blood vessels stained. p16 expression was evaluated by scoring positive nuclear reaction. Positive expression was demonstrated for all examined antigens, but their level of expression differed depending on the grades of tumour malignancy. Statistical analysis of the results documented a pronounced positive correlation between the markers studied and the grade of tumour malignancy (P < 0.001). It was shown that each of the cell markers examined represents a useful prognostic indicator for patients with mast cell tumours. The calculated correlation coefficients demonstrate a strong association between the expressions of CD117, FVIII and p16, and the histological malignancy of a tumour
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