Interpretable Machine Learning Methods Applied to Jet Background Subtraction in Heavy Ion Collisions

Jet measurements in heavy ion collisions can provide constraints on the properties of the quark gluon plasma, but the kinematic reach is limited by a large, fluctuating background. We present a novel application of symbolic regression to extract a functional representation of a deep neural network trained to subtract the background for measurements of jets in relativistic heavy ion collisions. We show that the deep neural network is approximately the same as a method using the particle multiplicity in a jet. This demonstrates that interpretable machine learning methods can provide insight into underlying physical processes

Multiplicity Based Background Subtraction for Jets in Heavy Ion Collisions

Jet measurements in heavy ion collisions at low jet momentum can provide constraints on the properties of the quark gluon plasma but are overwhelmed by a significant, fluctuating background. We build upon our previous work which demonstrated the ability of the jet multiplicity method to extend jet measurements into the domain of low jet momentum [1, Mengel:2023]. We extend this method to a wide range of jet resolution parameters. We investigate the over-complexity of non-interpretable machine learning used to tackle the problem of jet background subtraction through network optimization. Finally, we show that the resulting shallow neural network is able to learn the underlying relationship between jet multiplicity and background fluctuations, with a lesser complexity, reinforcing the utility of interpretable methods.Comment: 14 pages including references. 10 figures. 1 appendi

Modelling height in adolescence: a comparison of methods for estimating the age at peak height velocity

Background: Controlling for maturational status and timing is crucial in lifecourse epidemiology. One popular non-invasive measure of maturity is the age at peak height velocity (PHV). There are several ways to estimate age at PHV, but it is unclear which of these to use in practice. Aim: To find the optimal approach for estimating age at PHV. Subjects and methods: Methods included the Preece & Baines non-linear growth model, multi-level models with fractional polynomials, SuperImposition by Translation And Rotation (SITAR) and functional data analysis. These were compared through a simulation study and using data from a large cohort of adolescent boys from the Christ’s Hospital School. Results: The SITAR model gave close to unbiased estimates of age at PHV, but convergence issues arose when measurement error was large. Preece & Baines achieved close to unbiased estimates, but shares similarity with the data generation model for our simulation study and was also computationally inefficient, taking 24 hours to fit the data from Christ’s Hospital School. Functional data analysis consistently converged, but had higher mean bias than SITAR. Almost all methods demonstrated strong correlations (r > 0.9) between true and estimated age at PHV. Conclusions: Both SITAR or the PBGM are useful models for adolescent growth and provide unbiased estimates of age at peak height velocity. Care should be taken as substantial bias and variance can occur with large measurement error

Economic migration, social cohesion and development: towards an integrated approach

Dans la déclaration finale de leur 8e conférence, les ministres européens responsables des questions de migration se sont engagés à promouvoir et à protéger les droits fondamentaux des migrants, avec une attention particulière portée à l'égalité de genre et aux droits des femmes, au renforcement du dialogue et de la coopération entre les pays d'accueil, de transit et d'origine, notamment en Europe, et à la promotion de la cohérence entre les politiques de migration, de développement et d'intégration à tous les niveaux (international, national, régional et local).Les ministres se sont également engagés à gérer les migrations économiques afin de favoriser le progrès économique et social dans les pays d'accueil, de transit et d'origine ; à renforcer la cohésion sociale en améliorant l'intégration des migrants et des personnes issues de l'immigration, et la réintégration des migrants qui retournent dans leur pays d'origine ; à renforcer la contribution des migrants et des personnes issues de l'immigration au développement dans les pays d'accueil et d'origine, et leur participation à des programmes de codéveloppement. Cet ouvrage a été préparé pour servir de support aux débats des ministres durant la conférence. Il présente les aspects et caractéristiques principaux des migrations dans les Etats membres du Conseil de l'Europe, analyse les problèmes soulevés par les migrations contemporaines et définit un programme d'action adapté.In the final declaration of their 8th conference, the European ministers responsible for migration affairs committed to promoting and protecting the human rights of migrants, with special attention to gender equality and the rights of women; to strengthening dialogue and co-operation between receiving, transit and origin countries, particularly within Europe; and to promoting coherence at all levels (international, national, regional and local) between migration, development and integration policies. The ministers also agreed to manage economic migration with a view to promoting economic and social progress in receiving, transit and origin countries; to enhance social cohesion by improving the integration of migrants and persons of immigrant background and the re-integration of migrants who return to their countries of origin; and to strengthen the contribution of migrants and persons of immigrant background to development in receiving and origin countries and their involvement in co-development programs. This report was prepared to support the ministerial debate during the conference. It presents the main aspects and characteristics of migration in the member states of the Council of Europe, analyses policy challenges raised by contemporary migration and identifies an integrated policy agenda.info:eu-repo/semantics/publishedVersio

Adaptation or constraint? Reference-dependent scatter in honey bee dances

The waggle dance of the honey bee is used to recruit nest mates to a resource. Dancer bees, however, may indicate many directions within a single dance bout; we show that this scatter in honey bee dances is strongly dependent on the sensory modality used to determine a reference angle in the dance. Dances with a visual reference are more precise than those with a gravity reference. This finding undermines the idea that scatter is introduced into dances, which the bees could perform more precisely, in order to spread recruits out over resource patches. It also calls into question reported interspecific differences that had been interpreted as adaptations of the dance to different habitats. Our results support a non-adaptive hypothesis: that dance scatter results from sensory and performance constraints, rather than modulation of the scatter by the dancing bee. However, an alternative adaptive hypothesis cannot be ruled out

The classical limit for a class of quantum baker's maps

We show that the class of quantum baker's maps defined by Schack and Caves have the proper classical limit provided the number of momentum bits approaches infinity. This is done by deriving a semi-classical approximation to the coherent-state propagator.Comment: 18 pages, 5 figure

A constitutive law for dense granular flows

A continuum description of granular flows would be of considerable help in predicting natural geophysical hazards or in designing industrial processes. However, the constitutive equations for dry granular flows, which govern how the material moves under shear, are still a matter of debate. One difficulty is that grains can behave like a solid (in a sand pile), a liquid (when poured from a silo) or a gas (when strongly agitated). For the two extreme regimes, constitutive equations have been proposed based on kinetic theory for collisional rapid flows, and soil mechanics for slow plastic flows. However, the intermediate dense regime, where the granular material flows like a liquid, still lacks a unified view and has motivated many studies over the past decade. The main characteristics of granular liquids are: a yield criterion (a critical shear stress below which flow is not possible) and a complex dependence on shear rate when flowing. In this sense, granular matter shares similarities with classical visco-plastic fluids such as Bingham fluids. Here we propose a new constitutive relation for dense granular flows, inspired by this analogy and recent numerical and experimental work. We then test our three-dimensional (3D) model through experiments on granular flows on a pile between rough sidewalls, in which a complex 3D flow pattern develops. We show that, without any fitting parameter, the model gives quantitative predictions for the flow shape and velocity profiles. Our results support the idea that a simple visco-plastic approach can quantitatively capture granular flow properties, and could serve as a basic tool for modelling more complex flows in geophysical or industrial applications.Comment: http://www.nature.com/nature/journal/v441/n7094/abs/nature04801.htm

Rural to Urban Migration and Changes in Cardiovascular risk Factors in Tanzania: A Prospective Cohort Study.

High levels of rural to urban migration are a feature of most African countries. Our aim was to investigate changes, and their determinants, in cardiovascular risk factors on rural to urban migration in Tanzania. Men and women (15 to 59 years) intending to migrate from Morogoro rural region to Dar es Salaam for at least 6 months were identified. Measurements were made at least one week but no more than one month prior to migration, and 1 to 3 monthly after migration. Outcome measures included body mass index, blood pressure, fasting lipids, and self reported physical activity and diet. One hundred and three men, 106 women, mean age 29 years, were recruited and 132 (63.2%) followed to 12 months. All the figures presented here refer to the difference between baseline and 12 months in these 132 individuals. Vigorous physical activity declined (79.4% to 26.5% in men, 37.8% to 15.6% in women, p < 0.001), and weight increased (2.30 kg men, 2.35 kg women, p < 0.001). Intake of red meat increased, but so did the intake of fresh fruit and vegetables. HDL cholesterol increased in men and women (0.24, 0.25 mmoll-1 respectively, p < 0.001); and in men, not women, total cholesterol increased (0.42 mmoll-1, p = 0.01), and triglycerides fell (0.31 mmoll-1, p = 0.034). Blood pressure appeared to fall in both men and women. For example, in men systolic blood pressure fell by 5.4 mmHg, p = 0.007, and in women by 8.6 mmHg, p = 0.001. The lower level of physical activity and increasing weight will increase the risk of diabetes and cardiovascular disease. However, changes in diet were mixed, and may have contributed to mixed changes in lipid profiles and a lack of rise in blood pressure. A better understanding of the changes occurring on rural to urban migration is needed to guide preventive measures

Chemical Defense by the Native Winter Ant (Prenolepis imparis) against the Invasive Argentine Ant (Linepithema humile)

The invasive Argentine ant (Linepithema humile) is established worldwide and displaces native ant species. In northern California, however, the native winter ant (Prenolepis imparis) persists in invaded areas. We found that in aggressive interactions between the two species, P. imparis employs a potent defensive secretion. Field observations were conducted at P. imparis nest sites both in the presence and absence of L. humile. These observations suggested and laboratory assays confirmed that P. imparis workers are more likely to secrete when outnumbered by L. humile. Workers of P. imparis were also more likely to secrete near their nest entrances than when foraging on trees. One-on-one laboratory trials showed that the P. imparis secretion is highly lethal to L. humile, causing 79% mortality. The nonpolar fraction of the secretion was chemically analyzed with gas chromatography/mass spectrometry, and found to be composed of long-chain and cyclic hydrocarbons. Chemical analysis of dissected P. imparis workers showed that the nonpolar fraction is derived from the Dufour's gland. Based on these conclusions, we hypothesize that this chemical defense may help P. imparis to resist displacement by L. humile