Numerical simulations of a flux rope ejection

Coronal mass ejections (CMEs) are the most violent phenomena observed on the Sun. One of the most successful models to explain CMEs is the flux rope ejection model, where a magnetic flux rope is expelled from the solar corona after a long phase along which the flux rope stays in equilibrium while magnetic energy is being accumulated. However, still many questions are outstanding on the detailed mechanism of the ejection and observations continuously provide new data to interpret and put in the context. Currently, extreme ultraviolet (EUV) images from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) are providing new insights into the early phase of CME evolution. In particular, observations show the ejection of magnetic flux ropes from the solar corona and how they evolve into CMEs. However, these observations are difficult to interpret in terms of basic physical mechanisms and quantities, thus, we need to compare equivalent quantities to test and improve our models. In our work, we intend to bridge the gap between models and observations with our model of flux rope ejection where we consistently describe the full life span of a flux rope from its formation to ejection. This is done by coupling the global non-linear force-free model (GNLFFF) built to describe the slow low- β formation phase, with a full MHD simulation run with the software MPI-AMRVAC, suitable to describe the fast MHD evolution of the flux rope ejection that happens in a heterogeneous β regime. We also explore the parameter space to identify the conditions upon which the ejection is favoured (gravity stratification and magnetic field intensity) and we produce synthesised AIA observations (171 Å and 211 Å). To carry this out, we run 3D MHD simulation in spherical coordinates where we include the role of thermal conduction and radiative losses, both of which are important for determining the temperature distribution of the solar corona during a CME. Our model of flux rope ejection is successful in realistically describing the entire life span of a flux rope and we also set some conditions for the backgroud solar corona to favour the escape of the flux rope, so that it turns into a CME. Furthermore, our MHD simulation reproduces many of the features found in the AIA observations.Publisher PDFPeer reviewe

The TOF detector of ALICE experiment: Analysis of the first cosmic data

ALICE@LHC is an experiment optimized for study of heavy-ions collisions (Pb-Pb up to 5.5ATeV). The main aim is the search for a new state of matter (called QGP) where quarks and gluons are deconfined. Particle identification is guaranteed by a set of detectors: one of these, the time-of-flight system plays an important role in the identification of charged hadrons (π,K, p) in the momentum range [0.5, 4] GeV/c. The first data-taking periods with cosmic rays have been a great chance to check the performance of the experimental apparatus and of the developed software for description, simulation, recostruction, visualization and analysis. A preliminary time resolution study on this cosmic rays data is presented

Functional adaptivity for digital library services in e-infrastructures: the gCube approach

We consider the problem of e-Infrastructures that wish to reconcile the generality of their services with the bespoke requirements of diverse user communities. We motivate the requirement of functional adaptivity in the context of gCube, a service-based system that integrates Grid and Digital Library technologies to deploy, operate, and monitor Virtual Research Environments defined over infrastructural resources. We argue that adaptivity requires mapping service interfaces onto multiple implementations, truly alternative interpretations of the same functionality. We then analyse two design solutions in which the alternative implementations are, respectively, full-fledged services and local components of a single service. We associate the latter with lower development costs and increased binding flexibility, and outline a strategy to deploy them dynamically as the payload of service plugins. The result is an infrastructure in which services exhibit multiple behaviours, know how to select the most appropriate behaviour, and can seamlessly learn new behaviours

Conflict of Interest, Bias, and Manipulation: Reassessing Prescriber Education and the Learned Intermediary Doctrine

The purpose of this essay is to explore how the pharmaceutical industry’s influence impacts the drug approval process and the resulting information provided by drug manufacturers to healthcare providers and ultimately to patients. For nearly half a century, United States courts have held under the Learned Intermediary Doctrine that the makers of prescription drugs are responsible for educating prescribers, not patients, about their products. The dialectic tension between corporate profits and required prescriber education calls into question the credibility of drug information from corporate, medical, and government sources. The key question to be addressed in this paper is, how credible is the information provided to prescribers by pharmaceutical manufacturers? Numerous critics have called into question the FDA’s ability to assure that medical drugs are safe and effective and the communication about them is accurate and unbiased. But the FDA is not the only healthcare organization that collaborates with the pharmaceutical industry and creates confusion and perpetuates deceptions. Medical schools accept money for clinical trials, provide researchers, and cooperate with pharmaceutical manufacturers much to the concern of numerous critics. In addition, clinical trials data, publications, and continuing education frequently lack credibility related to researcher/author bias and conflicts of interest. Unless the influence of the pharmaceutical industry on contemporary healthcare is markedly altered or eliminated, prescribers cannot rely on the information they are provided and therefore should not be held liable by the courts as learned intermediaries

Securitization, transparency, and liquidity

We present a model in which issuers of asset-backed securities choose to release coarse information to enhance the liquidity of their primary market, at the cost of reducing secondary market liquidity. The degree of transparency is inefficiently low if the social value of secondary market liquidity exceeds its private value. We show that various types of public intervention (mandatory transparency standards, provision of liquidity to distressed banks, or secondary market price support) have quite different welfare implications. Finally, we extend the model by endogenizing the private and social value of liquidity and the proportion of sophisticated investors

Unit equations and Fermat surfaces in positive characteristic

In this article we study the three-variable unit equation $x + y + z = 1$ to be solved in $x, y, z \in \mathcal{O}_S^\ast$, where $\mathcal{O}_S^\ast$ is the $S$-unit group of some global function field. We give upper bounds for the height of solutions and the number of solutions. We also apply these techniques to study the Fermat surface $x^N + y^N + z^N = 1$

Higher genus theory

In $1801$, Gauss found an explicit description, in the language of binary quadratic forms, for the $2$-torsion of the narrow class group and dual narrow class group of a quadratic number field. This is now known as Gauss's genus theory. In this paper we extend Gauss's work to the setting of multi-quadratic number fields. To this end, we introduce and parametrize the categories of expansion groups and expansion Lie algebras, giving an explicit description for the universal objects of these categories. This description is inspired by the ideas of Smith \cite{smith2} in his recent breakthrough on Goldfeld's conjecture and the Cohen--Lenstra conjectures. Our main result shows that the maximal unramified multi-quadratic extension $L$ of a multi-quadratic number field $K$ can be reconstructed from the set of generalized governing expansions supported in the set of primes that ramify in $K$. This provides an explicit description for the group $\text{Gal}(L/\mathbb{Q})$ and a systematic procedure to construct the field $L$. A special case of our main result gives a sharp upper bound for the size of $\text{Cl}^{+}(K)[2]$. For every positive integer $n$, we find infinitely many multi-quadratic number fields $K$ such that $[K:\mathbb{Q}]$ equals $2^n$ and $\text{Gal}(L/\mathbb{Q})$ is a universal expansion group. Such fields $K$ are obtained using Smith's notion of additive systems and their basic Ramsey-theoretic behavior