202 research outputs found
Studies of opinion stability for small dynamic networks with opportunistic agents
There are numerous examples of societies with extremely stable mix of
contrasting opinions. We argue that this stability is a result of an interplay
between society network topology adjustment and opinion changing processes. To
support this position we present a computer model of opinion formation based on
some novel assumptions, designed to bring the model closer to social reality.
In our model, the agents, in addition to changing their opinions due to
influence of the rest of society and external propaganda, have the ability to
modify their social network, forming links with agents sharing the same
opinions and cutting the links with those they disagree with. To improve the
model further we divide the agents into `fanatics' and `opportunists',
depending on how easy is to change their opinions. The simulations show
significant differences compared to traditional models, where network links are
static. In particular, for the dynamical model where inter-agent links are
adjustable, the final network structure and opinion distribution is shown to
resemble real world observations, such as social structures and persistence of
minority groups even when most of the society is against them and the
propaganda is strong.Comment: Revised version accepted by International Journal of Modern Physics C
Added analysis, references and a new figur
Potential implication of Paxillin in cancer establishment within the bone environment
Background: Bone metastases are a common feature of advanced prostatic malignancies. They are characterised by a unique prevalence of osteoblastic phenotype and a poor prognosis. Paxillin is a 68-kDa signal transduction adaptor and scaffold protein that contains motifs involved in the mediation of protein–protein interactions. The state of paxillin phosphorylation is central to determining a cell's ability to adhere, detach and migrate and hence has been linked to processes such as wound repair and tumour metastasis. The current study explored the impact of paxillin suppression on prostate and breast cancer cell function and their responsiveness to hepatocyte growth factor (HGF) and bone matrix extract (BME) in order to assess its potential to influence bone colonization and homing. Materials and Methods: Hammerhead ribozyme transgenes were used to knockdown the expression of paxillin in breast and prostate cancer cell lines. The impact on the cell growth, migration, adhesion and invasion was assessed using in vitro functional assays. In order to explore potential mechanisms, focal adhesion kinase (FAK) inhibitor was also used. Results: Knockdown of paxillin expression was observed in all tested cell lines following transfection with the ribozyme transgene. The knockdown of paxillin increased proliferation and invasiveness of LNCaP cells, with no effect on their attachment abilities. The opposite, however, is true for PC-3 cells where, following knockdown, cellular attachment was significantly reduced, while no significant changes in growth and invasiveness were detected. In the MDA-MB-231 breast cancer knockdown model, cells had little difference in proliferative rates and generally increased attachment and reduced invasive abilities. Treatments with HGF and BME had differential effects on targeted cells when compared to controls. Conclusion: These data suggest that paxillin appears to influence major cell functions in a diverse range of prostate and breast cancer models. The responsiveness of cells to environmental factors such as HGF or BME may be influenced by paxillin status, although this seems to be dependent on cell type
Statistical physics of the Schelling model of segregation
We investigate the static and dynamic properties of a celebrated model of
social segregation, providing a complete explanation of the mechanisms leading
to segregation both in one- and two-dimensional systems. Standard statistical
physics methods shed light on the rich phenomenology of this simple model,
exhibiting static phase transitions typical of kinetic constrained models,
nontrivial coarsening like in driven-particle systems and percolation-related
phenomena.Comment: 4 pages, 3 figure
An Agent-Based Model of Collective Emotions in Online Communities
We develop a agent-based framework to model the emergence of collective
emotions, which is applied to online communities. Agents individual emotions
are described by their valence and arousal. Using the concept of Brownian
agents, these variables change according to a stochastic dynamics, which also
considers the feedback from online communication. Agents generate emotional
information, which is stored and distributed in a field modeling the online
medium. This field affects the emotional states of agents in a non-linear
manner. We derive conditions for the emergence of collective emotions,
observable in a bimodal valence distribution. Dependent on a saturated or a
superlinear feedback between the information field and the agent's arousal, we
further identify scenarios where collective emotions only appear once or in a
repeated manner. The analytical results are illustrated by agent-based computer
simulations. Our framework provides testable hypotheses about the emergence of
collective emotions, which can be verified by data from online communities.Comment: European Physical Journal B (in press), version 2 with extended
introduction, clarification
Hypotensive effect of atorvastatin in hypertensive patients: the association among flow-mediated dilation, oxidative stress and endothelial dysfunction
Recycling of Pretreated Polyolefin-Based Ocean-Bound Plastic Waste by Incorporating Clay and Rubber
Plastic waste found in oceans has become a major concern because of its impact on marine organisms and human health. There is significant global interest in recycling these materials, but their reclamation, sorting, cleaning, and reprocessing, along with the degradation that occurs in the natural environment, all make it difficult to achieve high quality recycled resins from ocean plastic waste. To mitigate these limitations, various additives including clay and rubber were explored. In this study, we compounded different types of ocean-bound (o-HDPE and o-PP) and virgin polymers (v-LDPE and v-PS) with various additives including a functionalized clay, styrene-multi-block-copolymer (SMB), and ethylene-propylene-based rubber (EPR). Physical observation showed that all blends containing PS were brittle due to the weak interfaces between the polyolefin regions and the PS domains within the polymer blend matrix. Blends containing clay showed rough surfaces and brittleness because of the non-uniform distribution of clay particles in the polymer matrix. To evaluate the properties and compatibility of the blends, characterizations using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and small-amplitude oscillatory shear (SAOS) rheology were carried out. The polymer blend (v-LDPE, o-HDPE, o-PP) containing EPR showed improved elasticity. Incorporating additives such as rubber could improve the mechanical properties of polymer blends for recycling purposes
Interband mixing between two-dimensional states localized in a surface quantum well and heavy hole states of the valence band in narrow gap semiconductor
Theoretical calculations in the framework of Kane model have been carried out
in order to elucidate the role of interband mixing in forming the energy
spectrum of two-dimensional carriers, localized in a surface quantum well in
narrow gap semiconductor. Of interest was the mixing between the 2D states and
heavy hole states in the volume of semiconductor. It has been shown that the
interband mixing results in two effects: the broadening of 2D energy levels and
their shift, which are mostly pronounced for semiconductors with high doping
level. The interband mixing has been found to influence mostly the effective
mass of 2D carriers for large their concentration, whereas it slightly changes
the subband distribution in a wide concentration range.Comment: 12 pages (RevTEX) and 4 PostScript-figure
Band structure of semimagnetic Hg1-yMnyTe quantum wells
The band structure of semimagnetic Hg_1-yMn_yTe/Hg_1-xCd_xTe type-III quantum
wells has been calculated using eight-band kp model in an envelope function
approach. Details of the band structure calculations are given for the Mn free
case (y=0). A mean field approach is used to take the influence of the sp-d
exchange interaction on the band structure of QW's with low Mn concentrations
into account. The calculated Landau level fan diagram and the density of states
of a Hg_0.98Mn_0.02Te/Hg_0.3Cd_0.7Te QW are in good agreement with recent
experimental transport observations. The model can be used to interpret the
mutual influence of the two-dimensional confinement and the sp-d exchange
interaction on the transport properties of Hg_1-yMn_yTe/Hg_1-xCd_xTe QW's.Comment: 12 pages, 4 figure
Złożoność obrazu klinicznego i trudności terapeutyczne u 85-letniej pacjentki z migotaniem przedsionków
We present a case of 85-year-old patient diagnosed with ST-segment elevation myocardial infarction of anterior wall due to coronary embolism secondary to persistent atrial fibrillation. The patient was performed coronary angiography and aspiration thrombectomy. Due to lack of atherosclerotic lesions, there was no need of stent implantation. On echocardiography we found left atrium appendage thrombus. After she was given dual antiplatelet therapy and rivaroxaban, gastrointestinal bleeding was observed. After that incident rivaroxaban was discontinued, which has led to the right axillary artery embolism. Afterwords she was given therapy only with oral anticoagulant and qualified to left atrium appendage closure.W niniejszej pracy zaprezentowano przypadek 85-letniej pacjentki z wywiadem przetrwałego migotania przedsionków, z rozpoznanym zawałem serca (ściany przedniej) z uniesieniem odcinka ST w mechanizmie zatorowym. Pacjentka miała wykonaną koronarografię i trombektomię aspiracyjną. Ze względu na brak zmian miażdżycowych w naczyniach wieńcowych nie implantowano stentu. W badaniu echokardiograficznym stwierdzono skrzeplinę w uszku lewego przedsionka. U chorej zastosowano podwójną terapię przeciwpłytkową i riwaroksaban, po czym doszło do krwawienia z przewodu pokarmowego. Po tym incydencie odstawiono riwaroksaban, co doprowadziło do wystąpienia zatoru w tętnicy pachowej prawej. Wobec całokształtu obrazu klinicznego pacjentka otrzymała tylko doustny antykoagulant i została zakwalifikowana do zabiegu zamknięcia uszka lewego przedsionka
A bounded confidence approach to understanding user participation in peer production systems
Commons-based peer production does seem to rest upon a paradox. Although
users produce all contents, at the same time participation is commonly on a
voluntary basis, and largely incentivized by achievement of project's goals.
This means that users have to coordinate their actions and goals, in order to
keep themselves from leaving. While this situation is easily explainable for
small groups of highly committed, like-minded individuals, little is known
about large-scale, heterogeneous projects, such as Wikipedia.
In this contribution we present a model of peer production in a large online
community. The model features a dynamic population of bounded confidence users,
and an endogenous process of user departure. Using global sensitivity analysis,
we identify the most important parameters affecting the lifespan of user
participation. We find that the model presents two distinct regimes, and that
the shift between them is governed by the bounded confidence parameter. For low
values of this parameter, users depart almost immediately. For high values,
however, the model produces a bimodal distribution of user lifespan. These
results suggest that user participation to online communities could be
explained in terms of group consensus, and provide a novel connection between
models of opinion dynamics and commons-based peer production.Comment: 17 pages, 5 figures, accepted to SocInfo201
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