Observation and study of the X(3872) particle with the CMS experiment at LHC

The discovery of the $X(3872)$ resonance in the decay channel $J/\psi \pi^+ \pi^-$ by Belle Collaboration in $2003$ opened up a new chapter in the QCD landscape. Its subsequent observation in other experiments confirms the existence of this new particle. \\The properties of $X(3872)$ are not in agreement with being a charmonium state. Different interpretations are still under study. One possible option is that it is a molecule of $D^{*}$ mesons, another one is that it is a hybrid of bound state and a tetra-quarks state. \\In this thesis it will be reported the study of the $X(3872)$ particle in the CMS experiment, at LHC, in the $2010$ and a first view at the $2011$ data. The observed decay channel is that one into a $J/\psi$ (reconstructed with a muons pair) and a pions pair ($\pi^+ \pi^-$). \\The CMS experiment, one of the two general purpose experiments in the LHC collider, has an impressive performance in the tracks and muons detection and reconstruction, due to the superior tracking performances. This allows the detection of high purity signal for the $J/\psi$ mesons and to reconstruct the $X(3872)$ particle. \\In this thesis it will be shown the measurement procedure of the production cross section ratio of the $X(3872)$ and $\psi(2S)$ in the same decay channel, using the statistics collected by CMS at $\sqrt{s}=7\,TeV$ at LHC in $2010$, corresponding to $\sim 40\,pb^{-1}$ of integrated luminosity. The measurement of the ratio is convenient because of the cancellation of the errors, such the one of the luminosity and the one of the trigger. The value of the ratio is: $R= 0.084\,\pm0.017(stat.)\,\pm0.009(syst.)$. \\The increased number of reconstructed $X(3872)$, $5310\pm342$, in the $2011$ collisions permits to continue the study of this particle. More study is undergoing, in this thesis it will be also shown a preliminary look at the first part of the $2011$ data and a study of the non-prompt composition of the $X(3872)$ in the data

Hierarchical nanomechanics of collagen microfibrils

Collagen constitutes one third of the human proteome, providing mechanical stability, elasticity and strength to connective tissues. Collagen is also the dominating material in the extracellular matrix (ECM) and is thus crucial for cell differentiation, growth and pathology. However, fundamental questions remain with respect to the origin of the unique mechanical properties of collagenous tissues, and in particular its stiffness, extensibility and nonlinear mechanical response. By using x-ray diffraction data of a collagen fibril reported by Orgel et al. (Proceedings of the National Academy of Sciences USA, 2006) in combination with protein structure identification methods, here we present an experimentally validated model of the nanomechanics of a collagen microfibril that incorporates the full biochemical details of the amino acid sequence of the constituting molecules. We report the analysis of its mechanical properties under different levels of stress and solvent conditions, using a full-atomistic force field including explicit water solvent. Mechanical testing of hydrated collagen microfibrils yields a Young’s modulus of ≈300 MPa at small and ≈1.2 GPa at larger deformation in excess of 10% strain, in excellent agreement with experimental data. Dehydrated, dry collagen microfibrils show a significantly increased Young’s modulus of ≈1.8 to 2.25 GPa (or ≈6.75 times the modulus in the wet state) owing to a much tighter molecular packing, in good agreement with experimental measurements (where an increase of the modulus by ≈9 times was found). Our model demonstrates that the unique mechanical properties of collagen microfibrils can be explained based on their hierarchical structure, where deformation is mediated through mechanisms that operate at different hierarchical levels. Key mechanisms involve straightening of initially disordered and helically twisted molecules at small strains, followed by axial stretching of molecules, and eventual molecular uncoiling at extreme deformation. These mechanisms explain the striking difference of the modulus of collagen fibrils compared with single molecules, which is found in the range of 4.8±2 GPa or ≈10-20 times greater. These findings corroborate the notion that collagen tissue properties are highly scale dependent and nonlinear elastic, an issue that must be considered in the development of models that describe the interaction of cells with collagen in the extracellular matrix. A key impact the atomistic model of collagen microfibril mechanics reported here is that it enables the bottom-up elucidation of structure-property relationships in the broader class of collagen materials such as tendon or bone, including studies in the context of genetic disease where the incorporation of biochemical, genetic details in material models of connective tissue is essential

Fabrication strategies towards hydrogels for biomedical application: chemical and mechanical insights

This review aims at giving selected chemical and mechanical insights on design criteria that should be taken into account in hydrogel production for biomedical applications. Particular emphasis will be given to the chemical aspects involved in hydrogel design: macromer chemical composition, cross-linking strategies and chemistry towards “conventional” and smart/stimuliresponsive hydrogels. Mechanical properties of hydrogels in view of regenerative medicine applications will also be considered

Gouverner et punir en temps de crise économique. Les pratiques pénales dans la Belgique du milieu du XIXe siècle

À travers l’exploitation des statistiques officielles et des archives des parquets, cet article propose d’étudier la « répression ordinaire » dans la Belgique du milieu du XIXe siècle. Outre la question des acteurs, il s’agit de cibler plus largement les mécanismes et les logiques influençant peu ou prou le sort des affaires introduites dans le système pénal, depuis la plainte jusqu’à la peine. L’arrière-plan de crise de subsistance permet de révéler des lignes de fractures qui traversent les pratiques, de prendre la véritable mesure de la capacité organique des institutions et de poser la question de l’usage du pénal comme mode de gouvernement.Using official statistics and court archives, this article studies ordinary repression in mid 19th century Belgium. Besides asking about actors, there is a wider focusing on the mechanisms and logics determining the outcome of cases entering the penal system, from the complaint to the sentence. The deep economic crisis background shows up the fracture lines running through practices, allows us to accurately measure the organic capacity of institutions as well as to question the use of the penal as a means of government

Collision avoidance and dynamic modeling for wheeled mobile robots and industrial manipulators

Collision Avoidance and Dynamic Modeling are key topics for researchers dealing with mobile and industrial robotics. A wide variety of algorithms, approaches and methodologies have been exploited, designed or adapted to tackle the problems of finding safe trajectories for mobile robots and industrial manipulators, and of calculating reliable dynamics models able to capture expected and possible also unexpected behaviors of robots. The knowledge of these two aspects and their potential is important to ensure the efficient and correct functioning of Industry 4.0 plants such as automated warehouses, autonomous surveillance systems and assembly lines. Collision avoidance is a crucial aspect to improve automation and safety, and to solve the problem of planning collision-free trajectories in systems composed of multiple autonomous agents such as unmanned mobile robots and manipulators with several degrees of freedom. A rigorous and accurate model explaining the dynamics of robots, is necessary to tackle tasks such as simulation, torque estimation, reduction of mechanical vibrations and design of control law

Introduction

Les premières entreprises statistiques « modernes », qui ont vu le jour dès la fin du xviiie siècle, ont tôt fait d’intégrer en leur sein des composantes « judiciaire » et « pénale ». Tour à tour destinées à rationaliser les modes de gouvernement et à mieux connaître les phénomènes de criminalité, ces entreprises ont laissé derrière elles un patrimoine scientifique monumental. De cette fabuleuse épopée subsistent quelques « états », fiches, registres ou encore comptes intermédiaires, dissémin..