1,373 research outputs found
Getting the Best of Both Worlds? Developing Complementary Equation-Based and Agent-Based Models
We argue that building agent-based and equation-based versions of the same theoretical model is a fruitful way of gaining insights into real-world phenomena. We use the epistemological concept of âmodels as isolations and surrogate systemsâ as the philosophical underpinning of this argument. In particular, we show that agent-based and equation-based approaches align well when used simultaneously and, contrary to some common misconceptions, should be considered complements rather than substitutes. We illustrate the usefulness of the approach by examining a model of the long-run relationship between economic development and inequality (i.e., the Kuznets hypothesis)
Birth, life and survival of Tidal Dwarf Galaxies
Advances on the formation and survival of the so-called Tidal Dwarf Galaxies
(TDGs) are reviewed. The understanding on how objects of the mass of dwarf
galaxies may form in debris of galactic collisions has recently benefited from
the coupling of multi-wavelength observations with numerical simulations of
galaxy mergers. Nonetheless, no consensual scenario has yet emerged and as a
matter of fact the very definition of TDGs remains elusive. Their real
cosmological importance is also a matter of debate, their presence in our Local
Group of galaxies as well. Identifying old, evolved, TDGs among the population
of regular dwarf galaxies and satellites may not be straightforward. However a
number of specific properties (location, dark matter and metal content) that
objects of tidal origin should have are reminded here. Examples of newly
discovered genuine old TDGs around a nearby elliptical galaxy are finally
presented.Comment: 9 pages, 5 figures, invited talk at JENAM 2010 symposium on "Dwarf
Galaxies", v2:reference and acknowledgements update
Human-to-Human Interaction: the Killer Application of Ubiquitous Computing
Twenty-five years past the Weiser\u2019s vision of Ubiquitous Computing, and there is not a clear understanding of what is or is not a pervasive system. Due to the loose boundaries of such paradigm, almost any kind of remotely ac-cessible networked system is classified as a pervasive system. We think that that is mainly due to the lack of killer applications that could make this vi-sion clearer. Actually, we think that the most promising killer application is already here, but we are so used to it that we do not see it, as a perfect fitting of the Weiser\u2019s vision: the Human-to-Human Interaction mediated by com-puters
Social Institutions and Economic Inequality Modeling the onset of the Kuznets Curve
Theoretical models of the Kuznets Curve have been purely analytical with little contribution to the timing of the process and to the presence of additional mechanisms affecting its timing. This paper proposes an agent-based version of Acemoglu and Robinsons model of the political economy of the Kuznets Curve. In extending their analytical framework we include heterogeneity of agents' income and a mating mechanism that together represent elements of social mobility. These two simple changes proved to be enough to shed light on the length and timing before high inequality implies regime change. Thus, this work may contribute to an effective empirical assessment of the Kuznets curve as it explicitly considers the time dimension of the process and the e ects of considering social dynamics
Experimental Quantum Hamiltonian Learning
Efficiently characterising quantum systems, verifying operations of quantum
devices and validating underpinning physical models, are central challenges for
the development of quantum technologies and for our continued understanding of
foundational physics. Machine-learning enhanced by quantum simulators has been
proposed as a route to improve the computational cost of performing these
studies. Here we interface two different quantum systems through a classical
channel - a silicon-photonics quantum simulator and an electron spin in a
diamond nitrogen-vacancy centre - and use the former to learn the latter's
Hamiltonian via Bayesian inference. We learn the salient Hamiltonian parameter
with an uncertainty of approximately . Furthermore, an observed
saturation in the learning algorithm suggests deficiencies in the underlying
Hamiltonian model, which we exploit to further improve the model itself. We go
on to implement an interactive version of the protocol and experimentally show
its ability to characterise the operation of the quantum photonic device. This
work demonstrates powerful new quantum-enhanced techniques for investigating
foundational physical models and characterising quantum technologies
The politics of vibrant matter: consistency, containment and the concrete of Mussoliniâs bunker
This article explores the idea of how vibrancy can be produced. Specifically, the attempt is to investigate the multiplicities of vibrancy by considering one of Mussoliniâs bunkers. The author examines the location of the bunker in the EUR (Esposizione Universale Romana) neighbourhood in Rome, the bunkerâs materiality, and the context and social meaning of the bunker through a contemporary art exhibition called âConfrontiâ (Confrontations) that took place in the bunker in 2009. The article argues that while emphasizing matterâs inherent vibrancy may be useful in some cases, there is also merit in further unpacking the ways in which vibrancy is produced. In this example, the concrete bunker expresses vibrancy through the processes involved in the emergent material form, and in the sustained politics and social considerations embedded in valuing tangible urban heritage
Emergent global patterns of ecosystem structure and function from a mechanistic general ecosystem model
Anthropogenic activities are causing widespread degradation of ecosystems worldwide, threatening the ecosystem services upon which all human life depends. Improved understanding of this degradation is urgently needed to improve avoidance and mitigation measures. One tool to assist these efforts is predictive models of ecosystem structure and function that are mechanistic: based on fundamental ecological principles. Here we present the first mechanistic General Ecosystem Model (GEM) of ecosystem structure and function that is both global and applies in all terrestrial and marine environments. Functional forms and parameter values were derived from the theoretical and empirical literature where possible. Simulations of the fate of all organisms with body masses between 10 Âľg and 150,000 kg (a range of 14 orders of magnitude) across the globe led to emergent properties at individual (e.g., growth rate), community (e.g., biomass turnover rates), ecosystem (e.g., trophic pyramids), and macroecological scales (e.g., global patterns of trophic structure) that are in general agreement with current data and theory. These properties emerged from our encoding of the biology of, and interactions among, individual organisms without any direct constraints on the properties themselves. Our results indicate that ecologists have gathered sufficient information to begin to build realistic, global, and mechanistic models of ecosystems, capable of predicting a diverse range of ecosystem properties and their response to human pressures
Cold gas accretion in galaxies
Evidence for the accretion of cold gas in galaxies has been rapidly
accumulating in the past years. HI observations of galaxies and their
environment have brought to light new facts and phenomena which are evidence of
ongoing or recent accretion:
1) A large number of galaxies are accompanied by gas-rich dwarfs or are
surrounded by HI cloud complexes, tails and filaments. It may be regarded as
direct evidence of cold gas accretion in the local universe. It is probably the
same kind of phenomenon of material infall as the stellar streams observed in
the halos of our galaxy and M31. 2) Considerable amounts of extra-planar HI
have been found in nearby spiral galaxies. While a large fraction of this gas
is produced by galactic fountains, it is likely that a part of it is of
extragalactic origin. 3) Spirals are known to have extended and warped outer
layers of HI. It is not clear how these have formed, and how and for how long
the warps can be sustained. Gas infall has been proposed as the origin. 4) The
majority of galactic disks are lopsided in their morphology as well as in their
kinematics. Also here recent accretion has been advocated as a possible cause.
In our view, accretion takes place both through the arrival and merging of
gas-rich satellites and through gas infall from the intergalactic medium (IGM).
The infall may have observable effects on the disk such as bursts of star
formation and lopsidedness. We infer a mean ``visible'' accretion rate of cold
gas in galaxies of at least 0.2 Msol/yr. In order to reach the accretion rates
needed to sustain the observed star formation (~1 Msol/yr), additional infall
of large amounts of gas from the IGM seems to be required.Comment: To appear in Astronomy & Astrophysics Reviews. 34 pages.
Full-resolution version available at
http://www.astron.nl/~oosterlo/accretionRevie
Prostate transglutaminase (TGase-4) antagonizes the anti-tumour action of MDA-7/IL-24 in prostate cancer
Background
Transglutamiase-4 (TGase-4), also known as prostate transglutaminase, belongs to the TGase family and is uniquely expressed in the prostate gland. The functions of this interesting protein are not clearly defined. In the present study, we have investigated an unexpected link between TGase-4 and the melanoma differentiation-associated gene-7/interleukin-24 (MDA-7/IL-24), a cytokine known to regulate the growth and apoptosis of certain cancer and immune cells.
Methods
Frozen sections of normal and malignant human prostate tissues and human prostate cancer (PCa) cell lines PC-3 and CA-HPV-10, cell lines expressing low and high levels of TGase-4, and recombinant MDA-7/IL-24 (rhMDA-7/IL-24) were used. Expression construct for human TGase-4 was generated using a mammalian expression vector with full length human TGase-4 isolated from normal human prostate tissues. PC-3 cells were transfected with expression construct or control plasmid. Stably transfected cells for control transfection and TGase-4 over expression were created. Similarly, expression of TGase-4 in CA-HPV-10 cells were knocked down by way of ribozyme transgenes. Single and double immunofluorescence microscopy was used for localization and co-localization of TGase-4 and MDA-7/IL-24 in PCa tissues and cells with antibodies to TGase-4; MDA-7/IL-24; IL-20alpha; IL-20beta and IL-22R. Cell-matrix adhesion, attachment and migration were by electric cell substrate impedance sensing and growth by in vitro cell growth assay. A panel of small molecule inhibitors, including Akt, was used to determine signal pathways involving TGase-4 and MDA-7/IL-24.
Results
We initially noted that MDA-7 resulted in inhibition of cell adhesion, growth and migration of human PCa PC-3 cells which did not express TGase-4. However, after the cells over-expressed TGase-4 by way of transfection, the TGase-4 expressing cells lost their adhesion, growth and migratory inhibitory response to MDA-7. On the other hand, CA-HPV-10 cells, a cell type naturally expressing high levels of TGase-4, had a contrasting response to MDA-7 when compared with PC-3 cells. Inhibitor to Akt reversed the inhibitory effect of MDA-7, only in PC-3 control cells, but not the TGase-4 expressing PC-3 cells. In human prostate tissues, TGase-4 was found to have a good degree of co-localization with one of the MDA-7 receptor complexes, IL-20Ra.
Conclusion
The presence of TGase-4 has a biological impact on a prostate cancer cell's response to MDA-7. TGase-4, via mechanism(s) yet to be identified, blocked the action of MDA-7 in prostate cancer cells. This has an important implication when considering the use of MDA-7 as a potential anticancer cytokine in prostate cancer therapies
Health-related quality of life for pre-diabetic states and type 2 diabetes mellitus: a cross-sectional study in Västerbotten Sweden
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