894 research outputs found
Data-parallel agent-based microscopic road network simulation using graphics processing units
Road network microsimulation is computationally expensive, and existing state of the art commercial tools use task parallelism and coarse-grained data-parallelism for multi-core processors to achieve improved levels of performance. An alternative is to use Graphics Processing Units (GPUs) and fine-grained data parallelism. This paper describes a GPU accelerated agent based microsimulation model of a road network transport system. The performance for a procedurally generated grid network is evaluated against that of an equivalent multi-core CPU simulation. In order to utilise GPU architectures effectively the paper describes an approach for graph traversal of neighbouring information which is vital to providing high levels of computational performance. The graph traversal approach has been integrated within a GPU agent based simulation framework as a generalised message traversal technique for graph-based communication. Speed-ups of up to 43 × are demonstrated with increased performance scaling behaviour. Simulation of over half a million vehicles and nearly two million detectors at a rate of 25 × faster than real-time is obtained on a single GPU
Phenomenology of Pseudo Dirac Neutrinos
We formulate general conditions on neutrino mass matrices under
which a degenerate pair of neutrinos at a high scale would split at low scale
by radiative corrections involving only the standard model fields. This
generalizes the original observations of Wolfenstein on pseudo Dirac neutrinos
to three generations. A specific model involving partially broken discrete
symmetry and solving the solar and atmospheric anomalies is proposed. The
symmetry pattern of the model naturally generates two large angles one of which
can account for the large angle MSW solution to the solar neutrino problem.Comment: 15 pages LATE
Assessment of variability sources in grape ripening parameters by using FTIR and multivariate modelling
The variability in grape ripening is associated with the fact that each grape berry undergoes its own biochemical processes. Traditional viticulture manages this by averaging the physicochemical values of hundreds of grapes to make decisions. However, to obtain accurate results it is necessary to evaluate the different sources of variability, so exhaustive sampling is essential. In this article, the factors “grape maturity over time” and “position of the grape” (both in the grapevine and in the bunch/cluster) were considered and studied by analyzing the grapes with a portable ATR-FTIR instrument and evaluating the spectra obtained with ANOVA–simultaneous component analysis (ASCA). Ripeness over time was the main factor affecting the characteristics of the grapes. Position in the vine and in the bunch (in that order) were also significantly important, and their effect on the grapes evolves over time. In addition, it was also possible to predict basic oenological parameters (TSS and pH with errors of 0.3 °Brix and 0.7, respectively). Finally, a quality control chart was built based on the spectra obtained in the optimal state of ripening, which could be used to decide which grapes are suitable for harvest
A Software-Agnostic Agent-based Platform for Modelling Emerging Mobility Systems
Due to the rapidly accelerated innovation cycle in
transport and the emergence of new mobility concepts and
technologies, public authorities, policy makers, and transport
planners are currently in need of the tools for sustainable
spatial and transport planning in the new mobility era. In
this paper, a new modular, software-agnostic and activity-based
spatial and transport planning platform is designed, i.e, the
HARMONY Model Suite, that facilitates a novel integration of
new and existing spatial and transport modelling tools. The paper
focuses on describing the architecture of the platform and its
passenger mobility simulation framework, which integrates -in
an interoperable manner- activity-based models, mobility service
management, and traffic simulation tools for evaluating new
mobility system dynamics. The service management controllers
for new mobility concepts are discussed in more detail with
regards to their functionality and applicability
Two-Stage Inflation in Supergravity
We investigate the viability of a two-stage inflationary scenario in the
context of supergravity, so as to resolve the problem of initial conditions for
hybrid inflation. We allow for non-renormalizable terms in the superpotential
and consider the most general form of the Kahler potential and the gauge
kinetic function. We construct a model with two stages of inflation, the first
driven by D-term and the second by F-term energy density. The viability of this
scenario depends on the non-minimal terms in the Kahler potential, for which we
derive the necessary constraints.Comment: 25 pages, LaTeX file, 2 figures in eps format, minor corrections to
the tex
Transcriptional dissection of pancreatic tumors engrafted in mice.
BACKGROUND: Engraftment of primary pancreas ductal adenocarcinomas (PDAC) in mice to generate patient-derived xenograft (PDX) models is a promising platform for biological and therapeutic studies in this disease. However, these models are still incompletely characterized. Here, we measured the impact of the murine tumor environment on the gene expression of the engrafted human tumoral cells.
METHODS: We have analyzed gene expression profiles from 35 new PDX models and compared them with previously published microarray data of 18 PDX models, 53 primary tumors and 41 cell lines from PDAC. The results obtained in the PDAC system were further compared with public available microarray data from 42 PDX models, 108 primary tumors and 32 cell lines from hepatocellular carcinoma (HCC). We developed a robust analysis protocol to explore the gene expression space. In addition, we completed the analysis with a functional characterization of PDX models, including if changes were caused by murine environment or by serial passing.
RESULTS: Our results showed that PDX models derived from PDAC, or HCC, were clearly different to the cell lines derived from the same cancer tissues. Indeed, PDAC- and HCC-derived cell lines are indistinguishable from each other based on their gene expression profiles. In contrast, the transcriptomes of PDAC and HCC PDX models can be separated into two different groups that share some partial similarity with their corresponding original primary tumors. Our results point to the lack of human stromal involvement in PDXs as a major factor contributing to their differences from the original primary tumors. The main functional differences between pancreatic PDX models and human PDAC are the lower expression of genes involved in pathways related to extracellular matrix and hemostasis and the up- regulation of cell cycle genes. Importantly, most of these differences are detected in the first passages after the tumor engraftment.
CONCLUSIONS: Our results suggest that PDX models of PDAC and HCC retain, to some extent, a gene expression memory of the original primary tumors, while this pattern is not detected in conventional cancer cell lines. Expression changes in PDXs are mainly related to pathways reflecting the lack of human infiltrating cells and the adaptation to a new environment. We also provide evidence of the stability of gene expression patterns over subsequent passages, indicating early phases of the adaptation process
Dynamics of coupled bosonic systems with applications to preheating
Coupled, multi-field models of inflation can provide several attractive
features unavailable in the case of a single inflaton field. These models have
a rich dynamical structure resulting from the interaction of the fields and
their associated fluctuations. We present a formalism to study the
nonequilibrium dynamics of coupled scalar fields. This formalism solves the
problem of renormalizing interacting models in a transparent way using
dimensional regularization. The evolution is generated by a renormalized
effective Lagrangian which incorporates the dynamics of the mean fields and
their associated fluctuations at one-loop order. We apply our method to two
problems of physical interest: (i) a simple two-field model which exemplifies
applications to reheating in inflation, and (ii) a supersymmetric hybrid
inflation model. This second case is interesting because inflation terminates
via a smooth phase transition which gives rise to a spinodal instability in one
of the fields. We study the evolution of the zero mode of the fields and the
energy density transfer to the fluctuations from the mean fields. We conclude
that back reaction effects can be significant over a wide parameter range. In
particular for the supersymmetric hybrid model we find that particle production
can be suppressed due to these effects.Comment: 23 pages, 16 eps-figures, minor changes in the text, references
added, accepted for publication in PR
Predictive Framework with a Pair of Degenerate Neutrinos at a high scale
Radiative generation of the solar scale is discussed in the
presence of leptonic CP violation. We assume that both the solar scale and
are zero at a high scale and the weak radiative corrections generate
them. It is shown that all leptonic mass matrices satisfying these requirements
lead to a unique prediction for the solar scale in terms of the
radiative correction parameter , the physical solar (atmospheric)
mixing angles and the Majorana neutrino mass
probed in neutrinoless double beta decay. This relation is independent
of the mixing matrix and CP-violating phases at the high scale. The presence of
CP-violating phases leads to dilution in the solar mixing angle defined at the
high scale. Because of this, bi-maximal mixing pattern at the high energy leads
to large but non-maximal solar mixing in the low-energy theory. An illustrative
model with this feature is discussed.Comment: 15 pages, including a postscript figur
Supersymmetric D-term Inflation, Reheating and Affleck-Dine Baryogenesis
The phenomenology of supersymmetric models of inflation, where the
inflationary vacuum energy is dominated by D-terms of a U(1), is investigated.
Particular attention is paid to the questions of how to arrange for sufficient
e-folds of inflation to occur, what kind of thermal history is expected after
the end of inflation, and how to implement successful baryogenesis. Such models
are argued to require a more restrictive symmetry structure than previously
thought. In particular, it is non-trivial that the decays of the fields driving
D-inflation can reheat the universe in such a way as to avoid the strong
gravitino production constraints. We also show how the initial conditions for
Affleck-Dine baryogenesis can arise in these models and that the simplest flat
directions along which baryon number is generated can often be ruled out by the
constraints coming from decoherence of the condensate in a hot environment. At
the end, we find that successful reheating and baryogenesis can take place in a
large subset of D-inflationary models.Comment: 23 pages LaTe
Inflationary models with a flat potential enforced by non-abelian discrete gauge symmetries
Non-abelian discrete gauge symmetries can provide the inflaton with a flat
potential even when one takes into account gravitational strength effects. The
discreteness of the symmetries also provide special field values where
inflation can end via a hybrid type mechanism. An interesting feature of this
method is that it can naturally lead to extremely flat potentials and so, in
principle, to inflation at unusually low energy scales. Two examples of
effective field theories with this mechanism are given, one with a hybrid exit
and one with a mutated hybrid exit. They include an explicit example in which
the single field consistency condition is violated.Comment: 24 pages, uses revtex.sty, submitted to PRD (Nov. 1999) Final version
to appear in PRD. Background information on supergravity expande
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