977 resultados para Weak Decays
Resumo:
This dissertation concerns the well-posedness of the Navier-Stokes-Smoluchowski system. The system models a mixture of fluid and particles in the so-called bubbling regime. The compressible Navier-Stokes equations governing the evolution of the fluid are coupled to the Smoluchowski equation for the particle density at a continuum level. First, working on fixed domains, the existence of weak solutions is established using a three-level approximation scheme and based largely on the Lions-Feireisl theory of compressible fluids. The system is then posed over a moving domain. By utilizing a Brinkman-type penalization as well as penalization of the viscosity, the existence of weak solutions of the Navier-Stokes-Smoluchowski system is proved over moving domains. As a corollary the convergence of the Brinkman penalization is proved. Finally, a suitable relative entropy is defined. This relative entropy is used to establish a weak-strong uniqueness result for the Navier-Stokes-Smoluchowski system over moving domains, ensuring that strong solutions are unique in the class of weak solutions.
Resumo:
We describe a one-step bio-refinery process for shrimp composites by-products. Its originality lies in a simple rapid (6 h) biotechnological cuticle fragmentation process that recovers all major compounds (chitins, peptides and minerals in particular calcium). The process consists of a controlled exogenous enzymatic proteolysis in a food-grade acidic medium allowing chitin purification (solid phase), and recovery of peptides and minerals (liquid phase). At a pH of between 3.5 and 4, protease activity is effective, and peptides are preserved. Solid phase demineralization kinetics were followed for phosphoric, hydrochloric, acetic, formic and citric acids with pKa ranging from 2.1 to 4.76. Formic acid met the initial aim of (i) 99 % of demineralization yield and (ii) 95 % deproteinization yield at a pH close to 3.5 and a molar ratio of 1.5. The proposed one-step process is proven to be efficient. To formalize the necessary elements for the future optimization of the process, two models to predict shell demineralization kinetics were studied, one based on simplified physical considerations and a second empirical one. The first model did not accurately describe the kinetics for times exceeding 30 minutes, the empirical one performed adequately.
Resumo:
In this work, we study the Zeeman splitting effects in the parallel magnetic field versus temperature phase diagram of two-dimensional superconductors with one graphene-like band and the orbital effects of perpendicular magnetic fields in isotropic two-dimensional semi-metallic superconductors. We show that when parallel magnetic fields are applied to graphene and as the intraband interaction decreases to a critical value, the width of the metastability region present in the phase diagram decreases, vanishing completely at that critical value. In the case of two-band superconductors with one graphene-like band, a new critical interaction, associated primarily with the graphene-like band, is required in order for a second metastability region to be present in the phase diagram. For intermediate values of this interaction, a low-temperature first-order transition line bifurcates at an intermediate temperature into a first-order transition between superconducting phases and a second-order transition line between the normal and the superconducting states. In our study on the upper critical fields in generic semi-metallic superconductors, we find that the pair propagator decays faster than that of a superconductor with a metallic band. As result, the zero field band gap equation does not have solution for weak intraband interactions, meaning that there is a critical intraband interaction value in order for a superconducting phase to be present in semi-metallic superconductors. Finally, we show that the out-of-plane critical magnetic field versus temperature phase diagram displays a positive curvature, contrasting with the parabolic-like behaviour typical of metallic superconductors.
Resumo:
In this thesis we study weak isometries of Hamming spaces. These are permutations of a Hamming space that preserve some but not necessarily all distances. We wish to find conditions under which a weak isometry is in fact an isometry. This type of problem was first posed by Beckman and Quarles for Rn. In chapter 2 we give definitions pertinent to our research. The 3rd chapter focuses on some known results in this area with special emphasis on papers by V. Krasin as well as S. De Winter and M. Korb who solved this problem for the Boolean cube, that is, the binary Hamming space. We attempted to generalize some of their methods to the non-boolean case. The 4th chapter has our new results and is split into two major contributions. Our first contribution shows if n=p or p < n2, then every weak isometry of Hnq that preserves distance p is an isometry. Our second contribution gives a possible method to check if a weak isometry is an isometry using linear algebra and graph theory.
Resumo:
The results of two separate searches for the rare two-body charmless baryonic decays B0 -> p pbar and B0s -> p pbar at the LHCb experiment are reported in this thesis. The first analysis uses a data sample, corresponding to an integrated luminosity of 0.9 fb^-1, of proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 7 TeV. An excess of B0 -> p pbar candidates with respect to background expectations is seen with a statistical significance of 3.3 standard deviations. This constitutes the first evidence for a two-body charmless baryonic B0 decay. No significant B0s -> p pbar signal was observed. However, a small excess of B0s -> p pbar events allowed the extraction of two sided confidence level intervals for the B0s -> p pbar branching fraction using the Feldman-Cousins frequentist method. This improved the upper limit on the B0s -> p pbar branching fraction by three orders of magnitude over previous bounds. The 68.3% confidence level intervals on the branching fractions were measured to be BF(B0 -> p pbar) = ( 1.47 ^{+0.62}_{-0.51} ^{+0.35}_{-0.14} ) x 10^-8, BF(B0s -> p pbar) = ( 2.84 ^{+2.03}_{-1.68} ^{+0.85}_{-0.18} ) x 10^-8, where the first uncertainty is statistical and the second is systematic. The second analysis followed on from the first LHCb result and included the full 2011 and 2012 samples of proton-proton collision data at centre of mass energies of 7 and 8 TeV, corresponding to a total integrated luminosity of 3.122 fb^-1.
Resumo:
A search for time-integrated violation of the CP symmetry, ACP(K−K+), in the Cabibbo-suppressed D0 → K−K+ decays is performed at the LHCb detector using proton- proton collisions recorded from 2015 to 2018 at the centre of mass energy of 13 TeV. The data used corresponds to an integrated luminosity of 5.7 fb−1. The flavour of the charm mesons is defined from the charge of the pion in D∗+ → D0π+ and D∗− → D0π− decays. Nuisance asymmetries are constrained from D∗+ → D0(→ K−π+)π+, D+ → KS0π+, D+ → K−π+π+, Ds+ → KS0K+ and Ds+ → φπ+ decays. The ACP(K−K+) asymme- try is measured to be ACP (K−K+) = (6.8 ± 5.4 (stat) ± 1.6 (syst)) · 10−4, in agreement with the previous LHCb results and the current world average. This represents the world’s most precise measurement of this quantity to date. Combining ACP (K−K+) with the time-integrated CP asymmetry difference, ∆ACP = ACP (K−K+)− ACP (π−π+), and the time-dependent CP asymmetry, ∆Y , measured with D0 → K−K+ and D0 → π−π+ decays, the direct CP asymmetries in D0 → K−K+ and D0 → π−π+ decays, adKK and adππ, result to be adKK =(7.7±5.7)·10−4, adππ =(23.2±6.1)·10−4, where the errors include systematic and statistical uncertainties and the correlation be- tween the two values is ρ(adKK,adππ) = 0.88. The values differ from zero for 1.4 and 3.8 standard deviations, respectively. In particular, adππ shows an evidence for direct CP violation in D0 → π−π+ decays.
Resumo:
The time-dependent CP asymmetries of the $B^0\to\pi^+\pi^-$ and $B^0_s\toK^+K^-$ decays and the time-integrated CP asymmetries of the $B^0\toK^+\pi^-$ and $B^0_s\to\pi^+K^-$ decays are measured, using the $p-p$ collision data collected with the LHCb detector and corresponding to the full Run2. The results are compatible with previous determinations of these quantities from LHCb, except for the CP-violation parameters of the $B^0_s\to K^+K^-$ decays, that show a discrepancy exceeding 3 standard deviations between different data-taking periods. The investigations being conducted to understand the discrepancy are documented. The measurement of the CKM matrix element $|V_{cb}|$ using $B^0_{s}\to D^{(*)-}_s\mu^+ \nu_\mu$ is also reported, using the $p-p$ collision data collected with the LHCb detector and corresponding to the full Run1. The measurement leads to $|V_{cb}| = (41.4\pm0.6\pm0.9\pm1.2)\times 10^{-3}$, where the first uncertainty is statistical, the second is systematic, and the third is due to external inputs. This measurement is compatible with the world averages and constitutes the first measurement of $|V_{cb}|$ at a hadron collider and the absolute first one with decays of the $B^0_s$ meson. The analysis also provides the very first measurements of the branching ratio and form factors parameters of the signal decay modes. The study of the characteristics ruling the response of an electromagnetic calorimeter (ECAL) to profitably operate in the high luminosity regime foreseen for the Upgrade2 of LHCb is reported in the final part of this Thesis. A fast and flexible simulation framework is developed to this purpose. Physics performance of different configurations of the ECAL are evaluated using samples of fully simulated $B^0\to \pi^+\pi^-\pi^0$ and $B^0\to K^{*0}e^+e^-$ decays. The results are used to guide the development of the future ECAL and are reported in the Framework Technical Design Report of the LHCb Upgrade2 detector.
Resumo:
In the literature on philosophical practices, despite the crucial role that argumentation plays in these activities, no specific argumentative theories have ever been proposed to assist the figure of the facilitator in conducting philosophical dialogue and to enhance student’s critical thinking skills. The dissertation starts from a cognitive perspective that challenges the classic Cartesian notion of rationality by focusing on limits and biases of human reasoning. An argumentative model (WRAT – Weak Reasoning Argumentative Theory) is then outlined in order to respond to the needs of philosophical dialogue. After justifying the claim that this learning activity, among other inductive methodologies, is the most suitable for critical thinking education, I inquired into the specific goal of ‘arguing’ within this context by means of the tools provided by Speech Act Theory: the speaker’s intention is to construct new knowledge by questioning her own and other’s beliefs. The model proposed has been theorized on this assumption, starting from which the goals, and, in turn, the related norms, have been pinpointed. In order to include all the epistemic attitudes required to accomplish the complex task of arguing in philosophical dialogue, I needed to integrate two opposed cognitive accounts, Dual Process Theory and Evolutionary Approach, that, although they provide incompatible descriptions of reasoning, can be integrated to provide a normative account of argumentation. The model, apart from offering a theoretical contribution to argumentation studies, is designed to be applied to the Italian educational system, in particular to classes in technical and professional high schools belonging to the newly created network Inventio. This initiative is one of the outcomes of the research project by the same name, which also includes an original Syllabus, research seminars, a monitoring action and publications focused on introducing philosophy, in the form of workshop activities, into technical and professional schools.
Resumo:
This thesis presents a search for a sterile right-handed neutrino $N$ produced in $D_s$ meson decays, using proton-proton collisions collected by the CMS experiment at the LHC. The data set used for the analysis, the B-Parking data set, corresponds to an integrated luminosity of $41.7\,\textrm{fb}^{-1}$ and was collected during the 2018 data-taking period. The analysis is targeting the $D_s^+\rightarrow N(\rightarrow\mu^{\pm}\pi^{\mp})\mu^{+}$ decays, where the final state muons can have the same electric charge allowing for a lepton flavor violating decay. To separate signal from background, a cut-based analysis is optimized using requirements on the sterile neutrino vertex displacement, muon and pion impact parameter, and impact parameter significance. The expected limit on the active-sterile neutrino mixing matrix parameter $|V_{\mu}|^2$ is extracted by performing a fit of the $\mu\pi$ invariant mass spectrum for two sterile neutrino mass hypotheses, 1.0 and 1.5 GeV. The analysis is currently blinded, following the internal CMS review process. The expected limit ranges between approximately $10^{-4}$ for a 1.0 GeV neutrino to $7\times10^{-5}$ for a 1.5 GeV neutrino. This is competitive with the best existing results from collider experiments over the same mass range.
Resumo:
The main aim of the thesis is to prove the local Lipschitz regularity of the weak solutions to a class of parabolic PDEs modeled on the parabolic p-Laplacian. This result is well known in the Euclidean case and recently has been extended in the Heisenberg group, while higher regularity results are not known in subriemannian parabolic setting. In this thesis we will consider vector fields more general than those in the Heisenberg setting, introducing some technical difficulties. To obtain our main result we will use a Moser-like iteration. Due to the non linearity of the equation, we replace the usual parabolic cylinders with new ones, whose dimension also depends on the L^p norm of the solution. In addition, we deeply simplify the iterative procedure, using the standard Sobolev inequality, instead of the parabolic one.
Resumo:
The models of teaching social sciences and clinical practice are insufficient for the needs of practical-reflective teaching of social sciences applied to health. The scope of this article is to reflect on the challenges and perspectives of social science education for health professionals. In the 1950s the important movement bringing together social sciences and the field of health began, however weak credentials still prevail. This is due to the low professional status of social scientists in health and the ill-defined position of the social sciences professionals in the health field. It is also due to the scant importance attributed by students to the social sciences, the small number of professionals and the colonization of the social sciences by the biomedical culture in the health field. Thus, the professionals of social sciences applied to health are also faced with the need to build an identity, even after six decades of their presence in the field of health. This is because their ambivalent status has established them as a partial, incomplete and virtual presence, requiring a complex survival strategy in the nebulous area between social sciences and health.
Resumo:
Viscosupplements, used for treating joint and cartilage diseases, restore the rheological properties of synovial fluid, regulate joint homeostasis and act as scaffolds for cell growth and tissue regeneration. Most viscosupplements are hydrogels composed of hyaluronic acid (HA) microparticles suspended in fluid HA. These microparticles are crosslinked with chemicals to assure their stability against enzyme degradation and to prolong the action of the viscosupplement. However, the crosslinking also modifies the mechanical, swelling and rheological properties of the HA microparticle hydrogels, with consequences on the effectiveness of the application. The aim of this study is to correlate the crosslinking degree (CD) with these properties to achieve modulation of HA/DVS microparticles through CD control. Because divinyl sulfone (DVS) is the usual crosslinker of HA in viscosupplements, we examined the effects of CD by preparing HA microparticles at 1:1, 2:1, 3:1, and 5:1 HA/DVS mass ratios. The CD was calculated from inductively coupled plasma spectrometry data. HA microparticles were previously sized to a mean diameter of 87.5 µm. Higher CD increased the viscoelasticity and the extrusion force and reduced the swelling of the HA microparticle hydrogels, which also showed Newtonian pseudoplastic behavior and were classified as covalent weak. The hydrogels were not cytotoxic to fibroblasts according to an MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2014.
Resumo:
Very high field (29)Si-NMR measurements using a fully (29)Si-enriched URu(2)Si(2) single crystal were carried out in order to microscopically investigate the hidden order (HO) state and adjacent magnetic phases in the high field limit. At the lowest measured temperature of 0.4 K, a clear anomaly reflecting a Fermi surface instability near 22 T inside the HO state is detected by the (29)Si shift, (29)K(c). Moreover, a strong enhancement of (29)K(c) develops near a critical field H(c) ≃ 35.6 T, and the ^{29}Si-NMR signal disappears suddenly at H(c), indicating the total suppression of the HO state. Nevertheless, a weak and shifted (29)Si-NMR signal reappears for fields higher than H(c) at 4.2 K, providing evidence for a magnetic structure within the magnetic phase caused by the Ising-type anisotropy of the uranium ordered moments.